/*
 * KVM paravirt_ops implementation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 * Copyright IBM Corporation, 2007
 *   Authors: Anthony Liguori <aliguori@us.ibm.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kvm_para.h>
#include <linux/cpu.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/hardirq.h>

#define MMU_QUEUE_SIZE 1024

struct kvm_para_state {
        u8 mmu_queue[MMU_QUEUE_SIZE];
        int mmu_queue_len;
        enum paravirt_lazy_mode mode;
};

static DEFINE_PER_CPU(struct kvm_para_state, para_state);

static struct kvm_para_state *kvm_para_state(void)
{
        return &per_cpu(para_state, raw_smp_processor_id());
}

/*
 * No need for any "IO delay" on KVM
 */
static void kvm_io_delay(void)
{
}

static void kvm_mmu_op(void *buffer, unsigned len)
{
        int r;
        unsigned long a1, a2;

        do {
                a1 = __pa(buffer);
                a2 = 0;   /* on i386 __pa() always returns <4G */
                r = kvm_hypercall3(KVM_HC_MMU_OP, len, a1, a2);
                buffer += r;
                len -= r;
        } while (len);
}

static void mmu_queue_flush(struct kvm_para_state *state)
{
        if (state->mmu_queue_len) {
                kvm_mmu_op(state->mmu_queue, state->mmu_queue_len);
                state->mmu_queue_len = 0;
        }
}

static void kvm_deferred_mmu_op(void *buffer, int len)
{
        struct kvm_para_state *state = kvm_para_state();

        if (state->mode != PARAVIRT_LAZY_MMU) {
                kvm_mmu_op(buffer, len);
                return;
        }
        if (state->mmu_queue_len + len > sizeof state->mmu_queue)
                mmu_queue_flush(state);
        memcpy(state->mmu_queue + state->mmu_queue_len, buffer, len);
        state->mmu_queue_len += len;
}

static void kvm_mmu_write(void *dest, u64 val)
{
        __u64 pte_phys;
        struct kvm_mmu_op_write_pte wpte;

#ifdef CONFIG_HIGHPTE
        struct page *page;
        unsigned long dst = (unsigned long) dest;

        page = kmap_atomic_to_page(dest);
        pte_phys = page_to_pfn(page);
        pte_phys <<= PAGE_SHIFT;
        pte_phys += (dst & ~(PAGE_MASK));
#else
        pte_phys = (unsigned long)__pa(dest);
#endif
        wpte.header.op = KVM_MMU_OP_WRITE_PTE;
        wpte.pte_val = val;
        wpte.pte_phys = pte_phys;

        kvm_deferred_mmu_op(&wpte, sizeof wpte);
}

/*
 * We only need to hook operations that are MMU writes.  We hook these so that
 * we can use lazy MMU mode to batch these operations.  We could probably
 * improve the performance of the host code if we used some of the information
 * here to simplify processing of batched writes.
 */
static void kvm_set_pte(pte_t *ptep, pte_t pte)
{
        kvm_mmu_write(ptep, pte_val(pte));
}

static void kvm_set_pte_at(struct mm_struct *mm, unsigned long addr,
                           pte_t *ptep, pte_t pte)
{
        kvm_mmu_write(ptep, pte_val(pte));
}

static void kvm_set_pmd(pmd_t *pmdp, pmd_t pmd)
{
        kvm_mmu_write(pmdp, pmd_val(pmd));
}

#if PAGETABLE_LEVELS >= 3
#ifdef CONFIG_X86_PAE
static void kvm_set_pte_atomic(pte_t *ptep, pte_t pte)
{
        kvm_mmu_write(ptep, pte_val(pte));
}

static void kvm_set_pte_present(struct mm_struct *mm, unsigned long addr,
                                pte_t *ptep, pte_t pte)
{
        kvm_mmu_write(ptep, pte_val(pte));
}

static void kvm_pte_clear(struct mm_struct *mm,
                          unsigned long addr, pte_t *ptep)
{
        kvm_mmu_write(ptep, 0);
}

static void kvm_pmd_clear(pmd_t *pmdp)
{
        kvm_mmu_write(pmdp, 0);
}
#endif

static void kvm_set_pud(pud_t *pudp, pud_t pud)
{
        kvm_mmu_write(pudp, pud_val(pud));
}

#if PAGETABLE_LEVELS == 4
static void kvm_set_pgd(pgd_t *pgdp, pgd_t pgd)
{
        kvm_mmu_write(pgdp, pgd_val(pgd));
}
#endif
#endif /* PAGETABLE_LEVELS >= 3 */

static void kvm_flush_tlb(void)
{
        struct kvm_mmu_op_flush_tlb ftlb = {
                .header.op = KVM_MMU_OP_FLUSH_TLB,
        };

        kvm_deferred_mmu_op(&ftlb, sizeof ftlb);
}

static void kvm_release_pt(unsigned long pfn)
{
        struct kvm_mmu_op_release_pt rpt = {
                .header.op = KVM_MMU_OP_RELEASE_PT,
                .pt_phys = (u64)pfn << PAGE_SHIFT,
        };

        kvm_mmu_op(&rpt, sizeof rpt);
}

static void kvm_enter_lazy_mmu(void)
{
        struct kvm_para_state *state = kvm_para_state();

        paravirt_enter_lazy_mmu();
        state->mode = paravirt_get_lazy_mode();
}

static void kvm_leave_lazy_mmu(void)
{
        struct kvm_para_state *state = kvm_para_state();

        mmu_queue_flush(state);
        paravirt_leave_lazy(paravirt_get_lazy_mode());
        state->mode = paravirt_get_lazy_mode();
}

static void paravirt_ops_setup(void)
{
        pv_info.name = "KVM";
        pv_info.paravirt_enabled = 1;

        if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
                pv_cpu_ops.io_delay = kvm_io_delay;

        if (kvm_para_has_feature(KVM_FEATURE_MMU_OP)) {
                pv_mmu_ops.set_pte = kvm_set_pte;
                pv_mmu_ops.set_pte_at = kvm_set_pte_at;
                pv_mmu_ops.set_pmd = kvm_set_pmd;
#if PAGETABLE_LEVELS >= 3
#ifdef CONFIG_X86_PAE
                pv_mmu_ops.set_pte_atomic = kvm_set_pte_atomic;
                pv_mmu_ops.set_pte_present = kvm_set_pte_present;
                pv_mmu_ops.pte_clear = kvm_pte_clear;
                pv_mmu_ops.pmd_clear = kvm_pmd_clear;
#endif
                pv_mmu_ops.set_pud = kvm_set_pud;
#if PAGETABLE_LEVELS == 4
                pv_mmu_ops.set_pgd = kvm_set_pgd;
#endif
#endif
                pv_mmu_ops.flush_tlb_user = kvm_flush_tlb;
                pv_mmu_ops.release_pte = kvm_release_pt;
                pv_mmu_ops.release_pmd = kvm_release_pt;
                pv_mmu_ops.release_pud = kvm_release_pt;

                pv_mmu_ops.lazy_mode.enter = kvm_enter_lazy_mmu;
                pv_mmu_ops.lazy_mode.leave = kvm_leave_lazy_mmu;
        }
}

void __init kvm_guest_init(void)
{
        if (!kvm_para_available())
                return;

        paravirt_ops_setup();
}