/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2004-2006 Silicon Graphics, Inc.  All Rights Reserved.
 */


/*
 * Cross Partition Communication (XPC) partition support.
 *
 *      This is the part of XPC that detects the presence/absence of
 *      other partitions. It provides a heartbeat and monitors the
 *      heartbeats of other partitions.
 *
 */


#include <linux/kernel.h>
#include <linux/sysctl.h>
#include <linux/cache.h>
#include <linux/mmzone.h>
#include <linux/nodemask.h>
#include <asm/uncached.h>
#include <asm/sn/bte.h>
#include <asm/sn/intr.h>
#include <asm/sn/sn_sal.h>
#include <asm/sn/nodepda.h>
#include <asm/sn/addrs.h>
#include <asm/sn/xpc.h>


/* XPC is exiting flag */
int xpc_exiting;


/* SH_IPI_ACCESS shub register value on startup */
static u64 xpc_sh1_IPI_access;
static u64 xpc_sh2_IPI_access0;
static u64 xpc_sh2_IPI_access1;
static u64 xpc_sh2_IPI_access2;
static u64 xpc_sh2_IPI_access3;


/* original protection values for each node */
u64 xpc_prot_vec[MAX_NUMNODES];


/* this partition's reserved page pointers */
struct xpc_rsvd_page *xpc_rsvd_page;
static u64 *xpc_part_nasids;
static u64 *xpc_mach_nasids;
struct xpc_vars *xpc_vars;
struct xpc_vars_part *xpc_vars_part;

static int xp_nasid_mask_bytes; /* actual size in bytes of nasid mask */
static int xp_nasid_mask_words; /* actual size in words of nasid mask */


/*
 * For performance reasons, each entry of xpc_partitions[] is cacheline
 * aligned. And xpc_partitions[] is padded with an additional entry at the
 * end so that the last legitimate entry doesn't share its cacheline with
 * another variable.
 */
struct xpc_partition xpc_partitions[XP_MAX_PARTITIONS + 1];


/*
 * Generic buffer used to store a local copy of portions of a remote
 * partition's reserved page (either its header and part_nasids mask,
 * or its vars).
 */
char *xpc_remote_copy_buffer;
void *xpc_remote_copy_buffer_base;


/*
 * Guarantee that the kmalloc'd memory is cacheline aligned.
 */
void *
xpc_kmalloc_cacheline_aligned(size_t size, gfp_t flags, void **base)
{
        /* see if kmalloc will give us cachline aligned memory by default */
        *base = kmalloc(size, flags);
        if (*base == NULL) {
                return NULL;
        }
        if ((u64) *base == L1_CACHE_ALIGN((u64) *base)) {
                return *base;
        }
        kfree(*base);

        /* nope, we'll have to do it ourselves */
        *base = kmalloc(size + L1_CACHE_BYTES, flags);
        if (*base == NULL) {
                return NULL;
        }
        return (void *) L1_CACHE_ALIGN((u64) *base);
}


/*
 * Given a nasid, get the physical address of the  partition's reserved page
 * for that nasid. This function returns 0 on any error.
 */
static u64
xpc_get_rsvd_page_pa(int nasid)
{
        bte_result_t bte_res;
        s64 status;
        u64 cookie = 0;
        u64 rp_pa = nasid;      /* seed with nasid */
        u64 len = 0;
        u64 buf = buf;
        u64 buf_len = 0;
        void *buf_base = NULL;


        while (1) {

                status = sn_partition_reserved_page_pa(buf, &cookie, &rp_pa,
                                                                &len);

                dev_dbg(xpc_part, "SAL returned with status=%li, cookie="
                        "0x%016lx, address=0x%016lx, len=0x%016lx\n",
                        status, cookie, rp_pa, len);

                if (status != SALRET_MORE_PASSES) {
                        break;
                }

                if (L1_CACHE_ALIGN(len) > buf_len) {
                        kfree(buf_base);
                        buf_len = L1_CACHE_ALIGN(len);
                        buf = (u64) xpc_kmalloc_cacheline_aligned(buf_len,
                                                        GFP_KERNEL, &buf_base);
                        if (buf_base == NULL) {
                                dev_err(xpc_part, "unable to kmalloc "
                                        "len=0x%016lx\n", buf_len);
                                status = SALRET_ERROR;
                                break;
                        }
                }

                bte_res = xp_bte_copy(rp_pa, buf, buf_len,
                                        (BTE_NOTIFY | BTE_WACQUIRE), NULL);
                if (bte_res != BTE_SUCCESS) {
                        dev_dbg(xpc_part, "xp_bte_copy failed %i\n", bte_res);
                        status = SALRET_ERROR;
                        break;
                }
        }

        kfree(buf_base);

        if (status != SALRET_OK) {
                rp_pa = 0;
        }
        dev_dbg(xpc_part, "reserved page at phys address 0x%016lx\n", rp_pa);
        return rp_pa;
}


/*
 * Fill the partition reserved page with the information needed by
 * other partitions to discover we are alive and establish initial
 * communications.
 */
struct xpc_rsvd_page *
xpc_rsvd_page_init(void)
{
        struct xpc_rsvd_page *rp;
        AMO_t *amos_page;
        u64 rp_pa, nasid_array = 0;
        int i, ret;


        /* get the local reserved page's address */

        preempt_disable();
        rp_pa = xpc_get_rsvd_page_pa(cpuid_to_nasid(smp_processor_id()));
        preempt_enable();
        if (rp_pa == 0) {
                dev_err(xpc_part, "SAL failed to locate the reserved page\n");
                return NULL;
        }
        rp = (struct xpc_rsvd_page *) __va(rp_pa);

        if (rp->partid != sn_partition_id) {
                dev_err(xpc_part, "the reserved page's partid of %d should be "
                        "%d\n", rp->partid, sn_partition_id);
                return NULL;
        }

        rp->version = XPC_RP_VERSION;

        /* establish the actual sizes of the nasid masks */
        if (rp->SAL_version == 1) {
                /* SAL_version 1 didn't set the nasids_size field */
                rp->nasids_size = 128;
        }
        xp_nasid_mask_bytes = rp->nasids_size;
        xp_nasid_mask_words = xp_nasid_mask_bytes / 8;

        /* setup the pointers to the various items in the reserved page */
        xpc_part_nasids = XPC_RP_PART_NASIDS(rp);
        xpc_mach_nasids = XPC_RP_MACH_NASIDS(rp);
        xpc_vars = XPC_RP_VARS(rp);
        xpc_vars_part = XPC_RP_VARS_PART(rp);

        /*
         * Before clearing xpc_vars, see if a page of AMOs had been previously
         * allocated. If not we'll need to allocate one and set permissions
         * so that cross-partition AMOs are allowed.
         *
         * The allocated AMO page needs MCA reporting to remain disabled after
         * XPC has unloaded.  To make this work, we keep a copy of the pointer
         * to this page (i.e., amos_page) in the struct xpc_vars structure,
         * which is pointed to by the reserved page, and re-use that saved copy
         * on subsequent loads of XPC. This AMO page is never freed, and its
         * memory protections are never restricted.
         */
        if ((amos_page = xpc_vars->amos_page) == NULL) {
                amos_page = (AMO_t *) TO_AMO(uncached_alloc_page(0));
                if (amos_page == NULL) {
                        dev_err(xpc_part, "can't allocate page of AMOs\n");
                        return NULL;
                }

                /*
                 * Open up AMO-R/W to cpu.  This is done for Shub 1.1 systems
                 * when xpc_allow_IPI_ops() is called via xpc_hb_init().
                 */
                if (!enable_shub_wars_1_1()) {
                        ret = sn_change_memprotect(ia64_tpa((u64) amos_page),
                                        PAGE_SIZE, SN_MEMPROT_ACCESS_CLASS_1,
                                        &nasid_array);
                        if (ret != 0) {
                                dev_err(xpc_part, "can't change memory "
                                        "protections\n");
                                uncached_free_page(__IA64_UNCACHED_OFFSET |
                                                   TO_PHYS((u64) amos_page));
                                return NULL;
                        }
                }
        } else if (!IS_AMO_ADDRESS((u64) amos_page)) {
                /*
                 * EFI's XPBOOT can also set amos_page in the reserved page,
                 * but it happens to leave it as an uncached physical address
                 * and we need it to be an uncached virtual, so we'll have to
                 * convert it.
                 */
                if (!IS_AMO_PHYS_ADDRESS((u64) amos_page)) {
                        dev_err(xpc_part, "previously used amos_page address "
                                "is bad = 0x%p\n", (void *) amos_page);
                        return NULL;
                }
                amos_page = (AMO_t *) TO_AMO((u64) amos_page);
        }

        /* clear xpc_vars */
        memset(xpc_vars, 0, sizeof(struct xpc_vars));

        xpc_vars->version = XPC_V_VERSION;
        xpc_vars->act_nasid = cpuid_to_nasid(0);
        xpc_vars->act_phys_cpuid = cpu_physical_id(0);
        xpc_vars->vars_part_pa = __pa(xpc_vars_part);
        xpc_vars->amos_page_pa = ia64_tpa((u64) amos_page);
        xpc_vars->amos_page = amos_page;  /* save for next load of XPC */


        /* clear xpc_vars_part */
        memset((u64 *) xpc_vars_part, 0, sizeof(struct xpc_vars_part) *
                                                        XP_MAX_PARTITIONS);

        /* initialize the activate IRQ related AMO variables */
        for (i = 0; i < xp_nasid_mask_words; i++) {
                (void) xpc_IPI_init(XPC_ACTIVATE_IRQ_AMOS + i);
        }

        /* initialize the engaged remote partitions related AMO variables */
        (void) xpc_IPI_init(XPC_ENGAGED_PARTITIONS_AMO);
        (void) xpc_IPI_init(XPC_DISENGAGE_REQUEST_AMO);

        /* timestamp of when reserved page was setup by XPC */
        rp->stamp = CURRENT_TIME;

        /*
         * This signifies to the remote partition that our reserved
         * page is initialized.
         */
        rp->vars_pa = __pa(xpc_vars);

        return rp;
}


/*
 * Change protections to allow IPI operations (and AMO operations on
 * Shub 1.1 systems).
 */
void
xpc_allow_IPI_ops(void)
{
        int node;
        int nasid;


        // >>> Change SH_IPI_ACCESS code to use SAL call once it is available.

        if (is_shub2()) {
                xpc_sh2_IPI_access0 =
                        (u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH2_IPI_ACCESS0));
                xpc_sh2_IPI_access1 =
                        (u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH2_IPI_ACCESS1));
                xpc_sh2_IPI_access2 =
                        (u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH2_IPI_ACCESS2));
                xpc_sh2_IPI_access3 =
                        (u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH2_IPI_ACCESS3));

                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
                                                                -1UL);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
                                                                -1UL);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
                                                                -1UL);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
                                                                -1UL);
                }

        } else {
                xpc_sh1_IPI_access =
                        (u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH1_IPI_ACCESS));

                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
                                                                -1UL);

                        /*
                         * Since the BIST collides with memory operations on
                         * SHUB 1.1 sn_change_memprotect() cannot be used.
                         */
                        if (enable_shub_wars_1_1()) {
                                /* open up everything */
                                xpc_prot_vec[node] = (u64) HUB_L((u64 *)
                                                GLOBAL_MMR_ADDR(nasid,
                                                SH1_MD_DQLP_MMR_DIR_PRIVEC0));
                                HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid,
                                                SH1_MD_DQLP_MMR_DIR_PRIVEC0),
                                                                -1UL);
                                HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid,
                                                SH1_MD_DQRP_MMR_DIR_PRIVEC0),
                                                                -1UL);
                        }
                }
        }
}


/*
 * Restrict protections to disallow IPI operations (and AMO operations on
 * Shub 1.1 systems).
 */
void
xpc_restrict_IPI_ops(void)
{
        int node;
        int nasid;


        // >>> Change SH_IPI_ACCESS code to use SAL call once it is available.

        if (is_shub2()) {

                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
                                                        xpc_sh2_IPI_access0);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
                                                        xpc_sh2_IPI_access1);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
                                                        xpc_sh2_IPI_access2);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
                                                        xpc_sh2_IPI_access3);
                }

        } else {

                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
                                                        xpc_sh1_IPI_access);

                        if (enable_shub_wars_1_1()) {
                                HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid,
                                                SH1_MD_DQLP_MMR_DIR_PRIVEC0),
                                                        xpc_prot_vec[node]);
                                HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid,
                                                SH1_MD_DQRP_MMR_DIR_PRIVEC0),
                                                        xpc_prot_vec[node]);
                        }
                }
        }
}


/*
 * At periodic intervals, scan through all active partitions and ensure
 * their heartbeat is still active.  If not, the partition is deactivated.
 */
void
xpc_check_remote_hb(void)
{
        struct xpc_vars *remote_vars;
        struct xpc_partition *part;
        partid_t partid;
        bte_result_t bres;


        remote_vars = (struct xpc_vars *) xpc_remote_copy_buffer;

        for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {

                if (xpc_exiting) {
                        break;
                }

                if (partid == sn_partition_id) {
                        continue;
                }

                part = &xpc_partitions[partid];

                if (part->act_state == XPC_P_INACTIVE ||
                                part->act_state == XPC_P_DEACTIVATING) {
                        continue;
                }

                /* pull the remote_hb cache line */
                bres = xp_bte_copy(part->remote_vars_pa,
                                        (u64) remote_vars,
                                        XPC_RP_VARS_SIZE,
                                        (BTE_NOTIFY | BTE_WACQUIRE), NULL);
                if (bres != BTE_SUCCESS) {
                        XPC_DEACTIVATE_PARTITION(part,
                                                xpc_map_bte_errors(bres));
                        continue;
                }

                dev_dbg(xpc_part, "partid = %d, heartbeat = %ld, last_heartbeat"
                        " = %ld, heartbeat_offline = %ld, HB_mask = 0x%lx\n",
                        partid, remote_vars->heartbeat, part->last_heartbeat,
                        remote_vars->heartbeat_offline,
                        remote_vars->heartbeating_to_mask);

                if (((remote_vars->heartbeat == part->last_heartbeat) &&
                        (remote_vars->heartbeat_offline == 0)) ||
                             !xpc_hb_allowed(sn_partition_id, remote_vars)) {

                        XPC_DEACTIVATE_PARTITION(part, xpcNoHeartbeat);
                        continue;
                }

                part->last_heartbeat = remote_vars->heartbeat;
        }
}


/*
 * Get a copy of a portion of the remote partition's rsvd page.
 *
 * remote_rp points to a buffer that is cacheline aligned for BTE copies and
 * is large enough to contain a copy of their reserved page header and
 * part_nasids mask.
 */
static enum xpc_retval
xpc_get_remote_rp(int nasid, u64 *discovered_nasids,
                struct xpc_rsvd_page *remote_rp, u64 *remote_rp_pa)
{
        int bres, i;


        /* get the reserved page's physical address */

        *remote_rp_pa = xpc_get_rsvd_page_pa(nasid);
        if (*remote_rp_pa == 0) {
                return xpcNoRsvdPageAddr;
        }


        /* pull over the reserved page header and part_nasids mask */
        bres = xp_bte_copy(*remote_rp_pa, (u64) remote_rp,
                                XPC_RP_HEADER_SIZE + xp_nasid_mask_bytes,
                                (BTE_NOTIFY | BTE_WACQUIRE), NULL);
        if (bres != BTE_SUCCESS) {
                return xpc_map_bte_errors(bres);
        }


        if (discovered_nasids != NULL) {
                u64 *remote_part_nasids = XPC_RP_PART_NASIDS(remote_rp);


                for (i = 0; i < xp_nasid_mask_words; i++) {
                        discovered_nasids[i] |= remote_part_nasids[i];
                }
        }


        /* check that the partid is for another partition */

        if (remote_rp->partid < 1 ||
                                remote_rp->partid > (XP_MAX_PARTITIONS - 1)) {
                return xpcInvalidPartid;
        }

        if (remote_rp->partid == sn_partition_id) {
                return xpcLocalPartid;
        }


        if (XPC_VERSION_MAJOR(remote_rp->version) !=
                                        XPC_VERSION_MAJOR(XPC_RP_VERSION)) {
                return xpcBadVersion;
        }

        return xpcSuccess;
}


/*
 * Get a copy of the remote partition's XPC variables from the reserved page.
 *
 * remote_vars points to a buffer that is cacheline aligned for BTE copies and
 * assumed to be of size XPC_RP_VARS_SIZE.
 */
static enum xpc_retval
xpc_get_remote_vars(u64 remote_vars_pa, struct xpc_vars *remote_vars)
{
        int bres;


        if (remote_vars_pa == 0) {
                return xpcVarsNotSet;
        }

        /* pull over the cross partition variables */
        bres = xp_bte_copy(remote_vars_pa, (u64) remote_vars, XPC_RP_VARS_SIZE,
                                (BTE_NOTIFY | BTE_WACQUIRE), NULL);
        if (bres != BTE_SUCCESS) {
                return xpc_map_bte_errors(bres);
        }

        if (XPC_VERSION_MAJOR(remote_vars->version) !=
                                        XPC_VERSION_MAJOR(XPC_V_VERSION)) {
                return xpcBadVersion;
        }

        return xpcSuccess;
}


/*
 * Update the remote partition's info.
 */
static void
xpc_update_partition_info(struct xpc_partition *part, u8 remote_rp_version,
                struct timespec *remote_rp_stamp, u64 remote_rp_pa,
                u64 remote_vars_pa, struct xpc_vars *remote_vars)
{
        part->remote_rp_version = remote_rp_version;
        dev_dbg(xpc_part, "  remote_rp_version = 0x%016x\n",
                part->remote_rp_version);

        part->remote_rp_stamp = *remote_rp_stamp;
        dev_dbg(xpc_part, "  remote_rp_stamp (tv_sec = 0x%lx tv_nsec = 0x%lx\n",
                part->remote_rp_stamp.tv_sec, part->remote_rp_stamp.tv_nsec);

        part->remote_rp_pa = remote_rp_pa;
        dev_dbg(xpc_part, "  remote_rp_pa = 0x%016lx\n", part->remote_rp_pa);

        part->remote_vars_pa = remote_vars_pa;
        dev_dbg(xpc_part, "  remote_vars_pa = 0x%016lx\n",
                part->remote_vars_pa);

        part->last_heartbeat = remote_vars->heartbeat;
        dev_dbg(xpc_part, "  last_heartbeat = 0x%016lx\n",
                part->last_heartbeat);

        part->remote_vars_part_pa = remote_vars->vars_part_pa;
        dev_dbg(xpc_part, "  remote_vars_part_pa = 0x%016lx\n",
                part->remote_vars_part_pa);

        part->remote_act_nasid = remote_vars->act_nasid;
        dev_dbg(xpc_part, "  remote_act_nasid = 0x%x\n",
                part->remote_act_nasid);

        part->remote_act_phys_cpuid = remote_vars->act_phys_cpuid;
        dev_dbg(xpc_part, "  remote_act_phys_cpuid = 0x%x\n",
                part->remote_act_phys_cpuid);

        part->remote_amos_page_pa = remote_vars->amos_page_pa;
        dev_dbg(xpc_part, "  remote_amos_page_pa = 0x%lx\n",
                part->remote_amos_page_pa);

        part->remote_vars_version = remote_vars->version;
        dev_dbg(xpc_part, "  remote_vars_version = 0x%x\n",
                part->remote_vars_version);
}


/*
 * Prior code has determined the nasid which generated an IPI.  Inspect
 * that nasid to determine if its partition needs to be activated or
 * deactivated.
 *
 * A partition is consider "awaiting activation" if our partition
 * flags indicate it is not active and it has a heartbeat.  A
 * partition is considered "awaiting deactivation" if our partition
 * flags indicate it is active but it has no heartbeat or it is not
 * sending its heartbeat to us.
 *
 * To determine the heartbeat, the remote nasid must have a properly
 * initialized reserved page.
 */
static void
xpc_identify_act_IRQ_req(int nasid)
{
        struct xpc_rsvd_page *remote_rp;
        struct xpc_vars *remote_vars;
        u64 remote_rp_pa;
        u64 remote_vars_pa;
        int remote_rp_version;
        int reactivate = 0;
        int stamp_diff;
        struct timespec remote_rp_stamp = { 0, 0 };
        partid_t partid;
        struct xpc_partition *part;
        enum xpc_retval ret;


        /* pull over the reserved page structure */

        remote_rp = (struct xpc_rsvd_page *) xpc_remote_copy_buffer;

        ret = xpc_get_remote_rp(nasid, NULL, remote_rp, &remote_rp_pa);
        if (ret != xpcSuccess) {
                dev_warn(xpc_part, "unable to get reserved page from nasid %d, "
                        "which sent interrupt, reason=%d\n", nasid, ret);
                return;
        }

        remote_vars_pa = remote_rp->vars_pa;
        remote_rp_version = remote_rp->version;
        if (XPC_SUPPORTS_RP_STAMP(remote_rp_version)) {
                remote_rp_stamp = remote_rp->stamp;
        }
        partid = remote_rp->partid;
        part = &xpc_partitions[partid];


        /* pull over the cross partition variables */

        remote_vars = (struct xpc_vars *) xpc_remote_copy_buffer;

        ret = xpc_get_remote_vars(remote_vars_pa, remote_vars);
        if (ret != xpcSuccess) {

                dev_warn(xpc_part, "unable to get XPC variables from nasid %d, "
                        "which sent interrupt, reason=%d\n", nasid, ret);

                XPC_DEACTIVATE_PARTITION(part, ret);
                return;
        }


        part->act_IRQ_rcvd++;

        dev_dbg(xpc_part, "partid for nasid %d is %d; IRQs = %d; HB = "
                "%ld:0x%lx\n", (int) nasid, (int) partid, part->act_IRQ_rcvd,
                remote_vars->heartbeat, remote_vars->heartbeating_to_mask);

        if (xpc_partition_disengaged(part) &&
                                        part->act_state == XPC_P_INACTIVE) {

                xpc_update_partition_info(part, remote_rp_version,
                                        &remote_rp_stamp, remote_rp_pa,
                                        remote_vars_pa, remote_vars);

                if (XPC_SUPPORTS_DISENGAGE_REQUEST(part->remote_vars_version)) {
                        if (xpc_partition_disengage_requested(1UL << partid)) {
                                /*
                                 * Other side is waiting on us to disengage,
                                 * even though we already have.
                                 */
                                return;
                        }
                } else {
                        /* other side doesn't support disengage requests */
                        xpc_clear_partition_disengage_request(1UL << partid);
                }

                xpc_activate_partition(part);
                return;
        }

        DBUG_ON(part->remote_rp_version == 0);
        DBUG_ON(part->remote_vars_version == 0);

        if (!XPC_SUPPORTS_RP_STAMP(part->remote_rp_version)) {
                DBUG_ON(XPC_SUPPORTS_DISENGAGE_REQUEST(part->
                                                        remote_vars_version));

                if (!XPC_SUPPORTS_RP_STAMP(remote_rp_version)) {
                        DBUG_ON(XPC_SUPPORTS_DISENGAGE_REQUEST(remote_vars->
                                                                version));
                        /* see if the other side rebooted */
                        if (part->remote_amos_page_pa ==
                                remote_vars->amos_page_pa &&
                                        xpc_hb_allowed(sn_partition_id,
                                                                remote_vars)) {
                                /* doesn't look that way, so ignore the IPI */
                                return;
                        }
                }

                /*
                 * Other side rebooted and previous XPC didn't support the
                 * disengage request, so we don't need to do anything special.
                 */

                xpc_update_partition_info(part, remote_rp_version,
                                                &remote_rp_stamp, remote_rp_pa,
                                                remote_vars_pa, remote_vars);
                part->reactivate_nasid = nasid;
                XPC_DEACTIVATE_PARTITION(part, xpcReactivating);
                return;
        }

        DBUG_ON(!XPC_SUPPORTS_DISENGAGE_REQUEST(part->remote_vars_version));

        if (!XPC_SUPPORTS_RP_STAMP(remote_rp_version)) {
                DBUG_ON(!XPC_SUPPORTS_DISENGAGE_REQUEST(remote_vars->version));

                /*
                 * Other side rebooted and previous XPC did support the
                 * disengage request, but the new one doesn't.
                 */

                xpc_clear_partition_engaged(1UL << partid);
                xpc_clear_partition_disengage_request(1UL << partid);

                xpc_update_partition_info(part, remote_rp_version,
                                                &remote_rp_stamp, remote_rp_pa,
                                                remote_vars_pa, remote_vars);
                reactivate = 1;

        } else {
                DBUG_ON(!XPC_SUPPORTS_DISENGAGE_REQUEST(remote_vars->version));

                stamp_diff = xpc_compare_stamps(&part->remote_rp_stamp,
                                                        &remote_rp_stamp);
                if (stamp_diff != 0) {
                        DBUG_ON(stamp_diff >= 0);

                        /*
                         * Other side rebooted and the previous XPC did support
                         * the disengage request, as does the new one.
                         */

                        DBUG_ON(xpc_partition_engaged(1UL << partid));
                        DBUG_ON(xpc_partition_disengage_requested(1UL <<
                                                                partid));

                        xpc_update_partition_info(part, remote_rp_version,
                                                &remote_rp_stamp, remote_rp_pa,
                                                remote_vars_pa, remote_vars);
                        reactivate = 1;
                }
        }

        if (part->disengage_request_timeout > 0 &&
                                        !xpc_partition_disengaged(part)) {
                /* still waiting on other side to disengage from us */
                return;
        }

        if (reactivate) {
                part->reactivate_nasid = nasid;
                XPC_DEACTIVATE_PARTITION(part, xpcReactivating);

        } else if (XPC_SUPPORTS_DISENGAGE_REQUEST(part->remote_vars_version) &&
                        xpc_partition_disengage_requested(1UL << partid)) {
                XPC_DEACTIVATE_PARTITION(part, xpcOtherGoingDown);
        }
}


/*
 * Loop through the activation AMO variables and process any bits
 * which are set.  Each bit indicates a nasid sending a partition
 * activation or deactivation request.
 *
 * Return #of IRQs detected.
 */
int
xpc_identify_act_IRQ_sender(void)
{
        int word, bit;
        u64 nasid_mask;
        u64 nasid;                      /* remote nasid */
        int n_IRQs_detected = 0;
        AMO_t *act_amos;


        act_amos = xpc_vars->amos_page + XPC_ACTIVATE_IRQ_AMOS;


        /* scan through act AMO variable looking for non-zero entries */
        for (word = 0; word < xp_nasid_mask_words; word++) {

                if (xpc_exiting) {
                        break;
                }

                nasid_mask = xpc_IPI_receive(&act_amos[word]);
                if (nasid_mask == 0) {
                        /* no IRQs from nasids in this variable */
                        continue;
                }

                dev_dbg(xpc_part, "AMO[%d] gave back 0x%lx\n", word,
                        nasid_mask);


                /*
                 * If this nasid has been added to the machine since
                 * our partition was reset, this will retain the
                 * remote nasid in our reserved pages machine mask.
                 * This is used in the event of module reload.
                 */
                xpc_mach_nasids[word] |= nasid_mask;


                /* locate the nasid(s) which sent interrupts */

                for (bit = 0; bit < (8 * sizeof(u64)); bit++) {
                        if (nasid_mask & (1UL << bit)) {
                                n_IRQs_detected++;
                                nasid = XPC_NASID_FROM_W_B(word, bit);
                                dev_dbg(xpc_part, "interrupt from nasid %ld\n",
                                        nasid);
                                xpc_identify_act_IRQ_req(nasid);
                        }
                }
        }
        return n_IRQs_detected;
}


/*
 * See if the other side has responded to a partition disengage request
 * from us.
 */
int
xpc_partition_disengaged(struct xpc_partition *part)
{
        partid_t partid = XPC_PARTID(part);
        int disengaged;


        disengaged = (xpc_partition_engaged(1UL << partid) == 0);
        if (part->disengage_request_timeout) {
                if (!disengaged) {
                        if (jiffies < part->disengage_request_timeout) {
                                /* timelimit hasn't been reached yet */
                                return 0;
                        }

                        /*
                         * Other side hasn't responded to our disengage
                         * request in a timely fashion, so assume it's dead.
                         */

                        dev_info(xpc_part, "disengage from remote partition %d "
                                "timed out\n", partid);
                        xpc_disengage_request_timedout = 1;
                        xpc_clear_partition_engaged(1UL << partid);
                        disengaged = 1;
                }
                part->disengage_request_timeout = 0;

                /* cancel the timer function, provided it's not us */
                if (!in_interrupt()) {
                        del_singleshot_timer_sync(&part->
                                                      disengage_request_timer);
                }

                DBUG_ON(part->act_state != XPC_P_DEACTIVATING &&
                                        part->act_state != XPC_P_INACTIVE);
                if (part->act_state != XPC_P_INACTIVE) {
                        xpc_wakeup_channel_mgr(part);
                }

                if (XPC_SUPPORTS_DISENGAGE_REQUEST(part->remote_vars_version)) {
                        xpc_cancel_partition_disengage_request(part);
                }
        }
        return disengaged;
}


/*
 * Mark specified partition as active.
 */
enum xpc_retval
xpc_mark_partition_active(struct xpc_partition *part)
{
        unsigned long irq_flags;
        enum xpc_retval ret;


        dev_dbg(xpc_part, "setting partition %d to ACTIVE\n", XPC_PARTID(part));

        spin_lock_irqsave(&part->act_lock, irq_flags);
        if (part->act_state == XPC_P_ACTIVATING) {
                part->act_state = XPC_P_ACTIVE;
                ret = xpcSuccess;
        } else {
                DBUG_ON(part->reason == xpcSuccess);
                ret = part->reason;
        }
        spin_unlock_irqrestore(&part->act_lock, irq_flags);

        return ret;
}


/*
 * Notify XPC that the partition is down.
 */
void
xpc_deactivate_partition(const int line, struct xpc_partition *part,
                                enum xpc_retval reason)
{
        unsigned long irq_flags;


        spin_lock_irqsave(&part->act_lock, irq_flags);

        if (part->act_state == XPC_P_INACTIVE) {
                XPC_SET_REASON(part, reason, line);
                spin_unlock_irqrestore(&part->act_lock, irq_flags);
                if (reason == xpcReactivating) {
                        /* we interrupt ourselves to reactivate partition */
                        xpc_IPI_send_reactivate(part);
                }
                return;
        }
        if (part->act_state == XPC_P_DEACTIVATING) {
                if ((part->reason == xpcUnloading && reason != xpcUnloading) ||
                                        reason == xpcReactivating) {
                        XPC_SET_REASON(part, reason, line);
                }
                spin_unlock_irqrestore(&part->act_lock, irq_flags);
                return;
        }

        part->act_state = XPC_P_DEACTIVATING;
        XPC_SET_REASON(part, reason, line);

        spin_unlock_irqrestore(&part->act_lock, irq_flags);

        if (XPC_SUPPORTS_DISENGAGE_REQUEST(part->remote_vars_version)) {
                xpc_request_partition_disengage(part);
                xpc_IPI_send_disengage(part);

                /* set a timelimit on the disengage request */
                part->disengage_request_timeout = jiffies +
                                        (xpc_disengage_request_timelimit * HZ);
                part->disengage_request_timer.expires =
                                        part->disengage_request_timeout;
                add_timer(&part->disengage_request_timer);
        }

        dev_dbg(xpc_part, "bringing partition %d down, reason = %d\n",
                XPC_PARTID(part), reason);

        xpc_partition_going_down(part, reason);
}


/*
 * Mark specified partition as inactive.
 */

void
xpc_mark_partition_inactive(struct xpc_partition *part)
{
        unsigned long irq_flags;


        dev_dbg(xpc_part, "setting partition %d to INACTIVE\n",
                XPC_PARTID(part));

        spin_lock_irqsave(&part->act_lock, irq_flags);
        part->act_state = XPC_P_INACTIVE;
        spin_unlock_irqrestore(&part->act_lock, irq_flags);
        part->remote_rp_pa = 0;
}


/*
 * SAL has provided a partition and machine mask.  The partition mask
 * contains a bit for each even nasid in our partition.  The machine
 * mask contains a bit for each even nasid in the entire machine.
 *
 * Using those two bit arrays, we can determine which nasids are
 * known in the machine.  Each should also have a reserved page
 * initialized if they are available for partitioning.
 */
void
xpc_discovery(void)
{
        void *remote_rp_base;
        struct xpc_rsvd_page *remote_rp;
        struct xpc_vars *remote_vars;
        u64 remote_rp_pa;
        u64 remote_vars_pa;
        int region;
        int region_size;
        int max_regions;
        int nasid;
        struct xpc_rsvd_page *rp;
        partid_t partid;
        struct xpc_partition *part;
        u64 *discovered_nasids;
        enum xpc_retval ret;


        remote_rp = xpc_kmalloc_cacheline_aligned(XPC_RP_HEADER_SIZE +
                                                xp_nasid_mask_bytes,
                                                GFP_KERNEL, &remote_rp_base);
        if (remote_rp == NULL) {
                return;
        }
        remote_vars = (struct xpc_vars *) remote_rp;


        discovered_nasids = kzalloc(sizeof(u64) * xp_nasid_mask_words,
                                                        GFP_KERNEL);
        if (discovered_nasids == NULL) {
                kfree(remote_rp_base);
                return;
        }

        rp = (struct xpc_rsvd_page *) xpc_rsvd_page;

        /*
         * The term 'region' in this context refers to the minimum number of
         * nodes that can comprise an access protection grouping. The access
         * protection is in regards to memory, IOI and IPI.
         */
        max_regions = 64;
        region_size = sn_region_size;

        switch (region_size) {
        case 128:
                max_regions *= 2;
        case 64:
                max_regions *= 2;
        case 32:
                max_regions *= 2;
                region_size = 16;
                DBUG_ON(!is_shub2());
        }

        for (region = 0; region < max_regions; region++) {

                if ((volatile int) xpc_exiting) {
                        break;
                }

                dev_dbg(xpc_part, "searching region %d\n", region);

                for (nasid = (region * region_size * 2);
                     nasid < ((region + 1) * region_size * 2);
                     nasid += 2) {

                        if ((volatile int) xpc_exiting) {
                                break;
                        }

                        dev_dbg(xpc_part, "checking nasid %d\n", nasid);


                        if (XPC_NASID_IN_ARRAY(nasid, xpc_part_nasids)) {
                                dev_dbg(xpc_part, "PROM indicates Nasid %d is "
                                        "part of the local partition; skipping "
                                        "region\n", nasid);
                                break;
                        }

                        if (!(XPC_NASID_IN_ARRAY(nasid, xpc_mach_nasids))) {
                                dev_dbg(xpc_part, "PROM indicates Nasid %d was "
                                        "not on Numa-Link network at reset\n",
                                        nasid);
                                continue;
                        }

                        if (XPC_NASID_IN_ARRAY(nasid, discovered_nasids)) {
                                dev_dbg(xpc_part, "Nasid %d is part of a "
                                        "partition which was previously "
                                        "discovered\n", nasid);
                                continue;
                        }


                        /* pull over the reserved page structure */

                        ret = xpc_get_remote_rp(nasid, discovered_nasids,
                                              remote_rp, &remote_rp_pa);
                        if (ret != xpcSuccess) {
                                dev_dbg(xpc_part, "unable to get reserved page "
                                        "from nasid %d, reason=%d\n", nasid,
                                        ret);

                                if (ret == xpcLocalPartid) {
                                        break;
                                }
                                continue;
                        }

                        remote_vars_pa = remote_rp->vars_pa;

                        partid = remote_rp->partid;
                        part = &xpc_partitions[partid];


                        /* pull over the cross partition variables */

                        ret = xpc_get_remote_vars(remote_vars_pa, remote_vars);
                        if (ret != xpcSuccess) {
                                dev_dbg(xpc_part, "unable to get XPC variables "
                                        "from nasid %d, reason=%d\n", nasid,
                                        ret);

                                XPC_DEACTIVATE_PARTITION(part, ret);
                                continue;
                        }

                        if (part->act_state != XPC_P_INACTIVE) {
                                dev_dbg(xpc_part, "partition %d on nasid %d is "
                                        "already activating\n", partid, nasid);
                                break;
                        }

                        /*
                         * Register the remote partition's AMOs with SAL so it
                         * can handle and cleanup errors within that address
                         * range should the remote partition go down. We don't
                         * unregister this range because it is difficult to
                         * tell when outstanding writes to the remote partition
                         * are finished and thus when it is thus safe to
                         * unregister. This should not result in wasted space
                         * in the SAL xp_addr_region table because we should
                         * get the same page for remote_act_amos_pa after
                         * module reloads and system reboots.
                         */
                        if (sn_register_xp_addr_region(
                                            remote_vars->amos_page_pa,
                                                        PAGE_SIZE, 1) < 0) {
                                dev_dbg(xpc_part, "partition %d failed to "
                                        "register xp_addr region 0x%016lx\n",
                                        partid, remote_vars->amos_page_pa);

                                XPC_SET_REASON(part, xpcPhysAddrRegFailed,
                                                __LINE__);
                                break;
                        }

                        /*
                         * The remote nasid is valid and available.
                         * Send an interrupt to that nasid to notify
                         * it that we are ready to begin activation.
                         */
                        dev_dbg(xpc_part, "sending an interrupt to AMO 0x%lx, "
                                "nasid %d, phys_cpuid 0x%x\n",
                                remote_vars->amos_page_pa,
                                remote_vars->act_nasid,
                                remote_vars->act_phys_cpuid);

                        if (XPC_SUPPORTS_DISENGAGE_REQUEST(remote_vars->
                                                                version)) {
                                part->remote_amos_page_pa =
                                                remote_vars->amos_page_pa;
                                xpc_mark_partition_disengaged(part);
                                xpc_cancel_partition_disengage_request(part);
                        }
                        xpc_IPI_send_activate(remote_vars);
                }
        }

        kfree(discovered_nasids);
        kfree(remote_rp_base);
}


/*
 * Given a partid, get the nasids owned by that partition from the
 * remote partition's reserved page.
 */
enum xpc_retval
xpc_initiate_partid_to_nasids(partid_t partid, void *nasid_mask)
{
        struct xpc_partition *part;
        u64 part_nasid_pa;
        int bte_res;


        part = &xpc_partitions[partid];
        if (part->remote_rp_pa == 0) {
                return xpcPartitionDown;
        }

        memset(nasid_mask, 0, XP_NASID_MASK_BYTES);

        part_nasid_pa = (u64) XPC_RP_PART_NASIDS(part->remote_rp_pa);

        bte_res = xp_bte_copy(part_nasid_pa, (u64) nasid_mask,
                        xp_nasid_mask_bytes, (BTE_NOTIFY | BTE_WACQUIRE), NULL);

        return xpc_map_bte_errors(bte_res);
}