/*
 * Xen hypercall batching.
 *
 * Xen allows multiple hypercalls to be issued at once, using the
 * multicall interface.  This allows the cost of trapping into the
 * hypervisor to be amortized over several calls.
 *
 * This file implements a simple interface for multicalls.  There's a
 * per-cpu buffer of outstanding multicalls.  When you want to queue a
 * multicall for issuing, you can allocate a multicall slot for the
 * call and its arguments, along with storage for space which is
 * pointed to by the arguments (for passing pointers to structures,
 * etc).  When the multicall is actually issued, all the space for the
 * commands and allocated memory is freed for reuse.
 *
 * Multicalls are flushed whenever any of the buffers get full, or
 * when explicitly requested.  There's no way to get per-multicall
 * return results back.  It will BUG if any of the multicalls fail.
 *
 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
 */
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/debugfs.h>

#include <asm/xen/hypercall.h>

#include "multicalls.h"
#include "debugfs.h"

#define MC_BATCH        32

#define MC_DEBUG        1

#define MC_ARGS         (MC_BATCH * 16)


struct mc_buffer {
        struct multicall_entry entries[MC_BATCH];
#if MC_DEBUG
        struct multicall_entry debug[MC_BATCH];
        void *caller[MC_BATCH];
#endif
        unsigned char args[MC_ARGS];
        struct callback {
                void (*fn)(void *);
                void *data;
        } callbacks[MC_BATCH];
        unsigned mcidx, argidx, cbidx;
};

static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);

/* flush reasons 0- slots, 1- args, 2- callbacks */
enum flush_reasons
{
        FL_SLOTS,
        FL_ARGS,
        FL_CALLBACKS,

        FL_N_REASONS
};

#ifdef CONFIG_XEN_DEBUG_FS
#define NHYPERCALLS     40              /* not really */

static struct {
        unsigned histo[MC_BATCH+1];

        unsigned issued;
        unsigned arg_total;
        unsigned hypercalls;
        unsigned histo_hypercalls[NHYPERCALLS];

        unsigned flush[FL_N_REASONS];
} mc_stats;

static u8 zero_stats;

static inline void check_zero(void)
{
        if (unlikely(zero_stats)) {
                memset(&mc_stats, 0, sizeof(mc_stats));
                zero_stats = 0;
        }
}

static void mc_add_stats(const struct mc_buffer *mc)
{
        int i;

        check_zero();

        mc_stats.issued++;
        mc_stats.hypercalls += mc->mcidx;
        mc_stats.arg_total += mc->argidx;

        mc_stats.histo[mc->mcidx]++;
        for(i = 0; i < mc->mcidx; i++) {
                unsigned op = mc->entries[i].op;
                if (op < NHYPERCALLS)
                        mc_stats.histo_hypercalls[op]++;
        }
}

static void mc_stats_flush(enum flush_reasons idx)
{
        check_zero();

        mc_stats.flush[idx]++;
}

#else  /* !CONFIG_XEN_DEBUG_FS */

static inline void mc_add_stats(const struct mc_buffer *mc)
{
}

static inline void mc_stats_flush(enum flush_reasons idx)
{
}
#endif  /* CONFIG_XEN_DEBUG_FS */

void xen_mc_flush(void)
{
        struct mc_buffer *b = &__get_cpu_var(mc_buffer);
        int ret = 0;
        unsigned long flags;
        int i;

        BUG_ON(preemptible());

        /* Disable interrupts in case someone comes in and queues
           something in the middle */
        local_irq_save(flags);

        mc_add_stats(b);

        if (b->mcidx) {
#if MC_DEBUG
                memcpy(b->debug, b->entries,
                       b->mcidx * sizeof(struct multicall_entry));
#endif

                if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
                        BUG();
                for (i = 0; i < b->mcidx; i++)
                        if (b->entries[i].result < 0)
                                ret++;

#if MC_DEBUG
                if (ret) {
                        printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
                               ret, smp_processor_id());
                        dump_stack();
                        for (i = 0; i < b->mcidx; i++) {
                                printk(KERN_DEBUG "  call %2d/%d: op=%lu arg=[%lx] result=%ld\t%pF\n",
                                       i+1, b->mcidx,
                                       b->debug[i].op,
                                       b->debug[i].args[0],
                                       b->entries[i].result,
                                       b->caller[i]);
                        }
                }
#endif

                b->mcidx = 0;
                b->argidx = 0;
        } else
                BUG_ON(b->argidx != 0);

        for (i = 0; i < b->cbidx; i++) {
                struct callback *cb = &b->callbacks[i];

                (*cb->fn)(cb->data);
        }
        b->cbidx = 0;

        local_irq_restore(flags);

        WARN_ON(ret);
}

struct multicall_space __xen_mc_entry(size_t args)
{
        struct mc_buffer *b = &__get_cpu_var(mc_buffer);
        struct multicall_space ret;
        unsigned argidx = roundup(b->argidx, sizeof(u64));

        BUG_ON(preemptible());
        BUG_ON(b->argidx > MC_ARGS);

        if (b->mcidx == MC_BATCH ||
            (argidx + args) > MC_ARGS) {
                mc_stats_flush(b->mcidx == MC_BATCH ? FL_SLOTS : FL_ARGS);
                xen_mc_flush();
                argidx = roundup(b->argidx, sizeof(u64));
        }

        ret.mc = &b->entries[b->mcidx];
#ifdef MC_DEBUG
        b->caller[b->mcidx] = __builtin_return_address(0);
#endif
        b->mcidx++;
        ret.args = &b->args[argidx];
        b->argidx = argidx + args;

        BUG_ON(b->argidx > MC_ARGS);
        return ret;
}

struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
{
        struct mc_buffer *b = &__get_cpu_var(mc_buffer);
        struct multicall_space ret = { NULL, NULL };

        BUG_ON(preemptible());
        BUG_ON(b->argidx > MC_ARGS);

        if (b->mcidx == 0)
                return ret;

        if (b->entries[b->mcidx - 1].op != op)
                return ret;

        if ((b->argidx + size) > MC_ARGS)
                return ret;

        ret.mc = &b->entries[b->mcidx - 1];
        ret.args = &b->args[b->argidx];
        b->argidx += size;

        BUG_ON(b->argidx > MC_ARGS);
        return ret;
}

void xen_mc_callback(void (*fn)(void *), void *data)
{
        struct mc_buffer *b = &__get_cpu_var(mc_buffer);
        struct callback *cb;

        if (b->cbidx == MC_BATCH) {
                mc_stats_flush(FL_CALLBACKS);
                xen_mc_flush();
        }

        cb = &b->callbacks[b->cbidx++];
        cb->fn = fn;
        cb->data = data;
}

#ifdef CONFIG_XEN_DEBUG_FS

static struct dentry *d_mc_debug;

static int __init xen_mc_debugfs(void)
{
        struct dentry *d_xen = xen_init_debugfs();

        if (d_xen == NULL)
                return -ENOMEM;

        d_mc_debug = debugfs_create_dir("multicalls", d_xen);

        debugfs_create_u8("zero_stats", 0644, d_mc_debug, &zero_stats);

        debugfs_create_u32("batches", 0444, d_mc_debug, &mc_stats.issued);
        debugfs_create_u32("hypercalls", 0444, d_mc_debug, &mc_stats.hypercalls);
        debugfs_create_u32("arg_total", 0444, d_mc_debug, &mc_stats.arg_total);

        xen_debugfs_create_u32_array("batch_histo", 0444, d_mc_debug,
                                     mc_stats.histo, MC_BATCH);
        xen_debugfs_create_u32_array("hypercall_histo", 0444, d_mc_debug,
                                     mc_stats.histo_hypercalls, NHYPERCALLS);
        xen_debugfs_create_u32_array("flush_reasons", 0444, d_mc_debug,
                                     mc_stats.flush, FL_N_REASONS);

        return 0;
}
fs_initcall(xen_mc_debugfs);

#endif  /* CONFIG_XEN_DEBUG_FS */