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Message-ID: <5196349b-95dd-97ad-214a-0101e9e68cf9@loongson.cn>
Date: Tue, 20 Jun 2023 16:14:39 +0800
From: zhaotianrui <zhaotianrui@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>,
WANG Xuerui <kernel@...0n.name>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
loongarch@...ts.linux.dev, Jens Axboe <axboe@...nel.dk>,
Mark Brown <broonie@...nel.org>,
Alex Deucher <alexander.deucher@....com>,
Oliver Upton <oliver.upton@...ux.dev>, maobibo@...ngson.cn,
Xi Ruoyao <xry111@...111.site>, tangyouling@...ngson.cn
Subject: Re: [PATCH v14 19/30] LoongArch: KVM: Implement kvm mmu operations
在 2023/6/20 下午2:59, zhaotianrui 写道:
>
> 在 2023/6/19 下午6:30, Huacai Chen 写道:
>> Hi, Tianrui,
>>
>> On Mon, Jun 19, 2023 at 4:33 PM Tianrui Zhao
>> <zhaotianrui@...ngson.cn> wrote:
>>> Implement LoongArch kvm mmu, it is used to switch gpa to hpa when
>>> guest exit because of address translation exception. This patch
>>> implement allocate gpa page table, search gpa from it and flush guest
>>> gpa in the table.
>>>
>>> Reviewed-by: Bibo Mao <maobibo@...ngson.cn>
>>> Signed-off-by: Tianrui Zhao <zhaotianrui@...ngson.cn>
>>> ---
>>> arch/loongarch/kvm/mmu.c | 725
>>> +++++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 725 insertions(+)
>>> create mode 100644 arch/loongarch/kvm/mmu.c
>>>
>>> diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c
>>> new file mode 100644
>>> index 000000000000..d75446139546
>>> --- /dev/null
>>> +++ b/arch/loongarch/kvm/mmu.c
>>> @@ -0,0 +1,725 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Copyright (C) 2020-2023 Loongson Technology Corporation Limited
>>> + */
>>> +
>>> +#include <linux/highmem.h>
>>> +#include <linux/page-flags.h>
>>> +#include <linux/kvm_host.h>
>>> +#include <linux/uaccess.h>
>>> +#include <asm/mmu_context.h>
>>> +#include <asm/pgalloc.h>
>>> +#include <asm/tlb.h>
>>> +
>>> +/*
>>> + * KVM_MMU_CACHE_MIN_PAGES is the number of GPA page table
>>> translation levels
>>> + * for which pages need to be cached.
>>> + */
>>> +#define KVM_MMU_CACHE_MIN_PAGES (CONFIG_PGTABLE_LEVELS - 1)
>>> +
>>> +/**
>>> + * kvm_pgd_alloc() - Allocate and initialise a KVM GPA page directory.
>>> + *
>>> + * Allocate a blank KVM GPA page directory (PGD) for representing
>>> guest physical
>>> + * to host physical page mappings.
>>> + *
>>> + * Returns: Pointer to new KVM GPA page directory.
>>> + * NULL on allocation failure.
>>> + */
>>> +pgd_t *kvm_pgd_alloc(void)
>>> +{
>>> + pgd_t *pgd;
>>> +
>>> + pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, 0);
>>> + if (pgd)
>>> + pgd_init((void *)pgd);
>>> +
>>> + return pgd;
>>> +}
>>> +
>>> +/**
>>> + * kvm_walk_pgd() - Walk page table with optional allocation.
>>> + * @pgd: Page directory pointer.
>>> + * @addr: Address to index page table using.
>>> + * @cache: MMU page cache to allocate new page tables from, or
>>> NULL.
>>> + *
>>> + * Walk the page tables pointed to by @pgd to find the PTE
>>> corresponding to the
>>> + * address @addr. If page tables don't exist for @addr, they will
>>> be created
>>> + * from the MMU cache if @cache is not NULL.
>>> + *
>>> + * Returns: Pointer to pte_t corresponding to @addr.
>>> + * NULL if a page table doesn't exist for @addr and
>>> !@...he.
>>> + * NULL if a page table allocation failed.
>>> + */
>>> +static pte_t *kvm_walk_pgd(pgd_t *pgd, struct kvm_mmu_memory_cache
>>> *cache,
>>> + unsigned long addr)
>>> +{
>>> + p4d_t *p4d;
>>> + pud_t *pud;
>>> + pmd_t *pmd;
>>> +
>>> + pgd += pgd_index(addr);
>>> + if (pgd_none(*pgd)) {
>>> + /* Not used yet */
>>> + BUG();
>>> + return NULL;
>>> + }
>>> + p4d = p4d_offset(pgd, addr);
>>> + pud = pud_offset(p4d, addr);
>>> + if (pud_none(*pud)) {
>>> + pmd_t *new_pmd;
>>> +
>>> + if (!cache)
>>> + return NULL;
>>> + new_pmd = kvm_mmu_memory_cache_alloc(cache);
>>> + pmd_init((void *)new_pmd);
>>> + pud_populate(NULL, pud, new_pmd);
>>> + }
>>> + pmd = pmd_offset(pud, addr);
>>> + if (pmd_none(*pmd)) {
>>> + pte_t *new_pte;
>>> +
>>> + if (!cache)
>>> + return NULL;
>>> + new_pte = kvm_mmu_memory_cache_alloc(cache);
>>> + clear_page(new_pte);
>>> + pmd_populate_kernel(NULL, pmd, new_pte);
>>> + }
>>> + return pte_offset_kernel(pmd, addr);
>>> +}
>>> +
>>> +/* Caller must hold kvm->mm_lock */
>>> +static pte_t *kvm_pte_for_gpa(struct kvm *kvm,
>>> + struct kvm_mmu_memory_cache *cache,
>>> + unsigned long addr)
>>> +{
>>> + return kvm_walk_pgd(kvm->arch.gpa_mm.pgd, cache, addr);
>>> +}
>>> +
>>> +/*
>>> + * level2_flush_{pte,pmd,pud,pgd,pt}.
>>> + * Flush a range of guest physical address space from the VM's GPA
>>> page tables.
>>> + */
>> What's the meaning of level2 in this patch? It looks strange and I
>> haven't seen others use them, maybe we can use some better names.
>>
>> Huacai
> level2 means the address translation of gpa to hpa. As for level1, it
> means gva to gpa. The same as stage-2 in arm64 KVM.
>
> Thanks
> Tianrui Zhao
And there are some other archs KVM mmu name, such as gstage_mmu in
riscv, tdp(two dimension paging)_mmu in x86, stage2_mmu in arm64, so
what do you think of level2_mmu in our LoongArch KVM?
Thanks
Tianrui Zhao
>>
>>> +static int level2_flush_pte(pmd_t *pmd, unsigned long addr,
>>> unsigned long end)
>>> +{
>>> + pte_t *pte;
>>> + unsigned long next, start;
>>> + int ret;
>>> +
>>> + ret = 0;
>>> + start = addr;
>>> + pte = pte_offset_kernel(pmd, addr);
>>> + do {
>>> + next = addr + PAGE_SIZE;
>>> + if (!pte_present(*pte))
>>> + continue;
>>> +
>>> + set_pte(pte, __pte(0));
>>> + ret = 1;
>>> + } while (pte++, addr = next, addr != end);
>>> +
>>> + if (start + PMD_SIZE == end) {
>>> + pte = pte_offset_kernel(pmd, 0);
>>> + pmd_clear(pmd);
>>> + pte_free_kernel(NULL, pte);
>>> + }
>>> + return ret;
>>> +}
>>> +
>>> +static int level2_flush_pmd(pud_t *pud, unsigned long addr,
>>> unsigned long end)
>>> +{
>>> + pmd_t *pmd;
>>> + unsigned long next, start;
>>> + int ret;
>>> +
>>> + ret = 0;
>>> + start = addr;
>>> + pmd = pmd_offset(pud, addr);
>>> + do {
>>> + next = pmd_addr_end(addr, end);
>>> + if (!pmd_present(*pmd))
>>> + continue;
>>> +
>>> + ret |= level2_flush_pte(pmd, addr, next);
>>> + } while (pmd++, addr = next, addr != end);
>>> +
>>> + if (start + PUD_SIZE == end) {
>>> + pmd = pmd_offset(pud, 0);
>>> + pud_clear(pud);
>>> + pmd_free(NULL, pmd);
>>> + }
>>> + return ret;
>>> +}
>>> +
>>> +static int level2_flush_pud(pgd_t *pgd, unsigned long addr,
>>> unsigned long end)
>>> +{
>>> + p4d_t *p4d;
>>> + pud_t *pud;
>>> + unsigned long next, start;
>>> + int ret;
>>> +
>>> + ret = 0;
>>> + start = addr;
>>> + p4d = p4d_offset(pgd, addr);
>>> + pud = pud_offset(p4d, addr);
>>> + do {
>>> + next = pud_addr_end(addr, end);
>>> + if (!pud_present(*pud))
>>> + continue;
>>> +
>>> + ret |= level2_flush_pmd(pud, addr, next);
>>> + } while (pud++, addr = next, addr != end);
>>> +
>>> + if (start + PGDIR_SIZE == end) {
>>> + pud = pud_offset(p4d, 0);
>>> + pgd_clear(pgd);
>>> + pud_free(NULL, pud);
>>> + }
>>> + return ret;
>>> +}
>>> +
>>> +static int level2_flush_pgd(pgd_t *pgd, unsigned long addr,
>>> unsigned long end)
>>> +{
>>> + unsigned long next;
>>> + int ret;
>>> +
>>> + ret = 0;
>>> + if (addr > end - 1)
>>> + return ret;
>>> + pgd = pgd + pgd_index(addr);
>>> + do {
>>> + next = pgd_addr_end(addr, end);
>>> + if (!pgd_present(*pgd))
>>> + continue;
>>> +
>>> + ret |= level2_flush_pud(pgd, addr, next);
>>> + } while (pgd++, addr = next, addr != end);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +/**
>>> + * level2_flush_range() - Flush a range of guest physical addresses.
>>> + * @kvm: KVM pointer.
>>> + * @start_gfn: Guest frame number of first page in GPA range to flush.
>>> + * @end_gfn: Guest frame number of last page in GPA range to flush.
>>> + *
>>> + * Flushes a range of GPA mappings from the GPA page tables.
>>> + *
>>> + * The caller must hold the @kvm->mmu_lock spinlock.
>>> + *
>>> + * Returns: Whether its safe to remove the top level page
>>> directory because
>>> + * all lower levels have been removed.
>>> + */
>>> +static bool level2_flush_range(struct kvm *kvm, gfn_t start_gfn,
>>> gfn_t end_gfn)
>>> +{
>>> + return level2_flush_pgd(kvm->arch.gpa_mm.pgd, start_gfn <<
>>> PAGE_SHIFT,
>>> + end_gfn << PAGE_SHIFT);
>>> +}
>>> +
>>> +typedef int (*level2_pte_ops)(void *pte);
>>> +/*
>>> + * level2_mkclean_pte
>>> + * Mark a range of guest physical address space clean (writes
>>> fault) in the VM's
>>> + * GPA page table to allow dirty page tracking.
>>> + */
>>> +static int level2_mkclean_pte(void *pte)
>>> +{
>>> + pte_t val;
>>> +
>>> + val = *(pte_t *)pte;
>>> + if (pte_dirty(val)) {
>>> + *(pte_t *)pte = pte_mkclean(val);
>>> + return 1;
>>> + }
>>> + return 0;
>>> +}
>>> +
>>> +static int level2_ptw_pte(pmd_t *pmd, unsigned long addr, unsigned
>>> long end,
>>> + level2_pte_ops func)
>>> +{
>>> + pte_t *pte;
>>> + unsigned long next;
>>> + int ret;
>>> +
>>> + ret = 0;
>>> + pte = pte_offset_kernel(pmd, addr);
>>> + do {
>>> + next = addr + PAGE_SIZE;
>>> + if (!pte_present(*pte))
>>> + continue;
>>> +
>>> + ret |= func(pte);
>>> + } while (pte++, addr = next, addr != end);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +static int level2_ptw_pmd(pud_t *pud, unsigned long addr, unsigned
>>> long end,
>>> + level2_pte_ops func)
>>> +{
>>> + pmd_t *pmd;
>>> + unsigned long next;
>>> + int ret;
>>> +
>>> + ret = 0;
>>> + pmd = pmd_offset(pud, addr);
>>> + do {
>>> + next = pmd_addr_end(addr, end);
>>> + if (!pmd_present(*pmd))
>>> + continue;
>>> +
>>> + ret |= level2_ptw_pte(pmd, addr, next, func);
>>> + } while (pmd++, addr = next, addr != end);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +static int level2_ptw_pud(pgd_t *pgd, unsigned long addr, unsigned
>>> long end,
>>> + level2_pte_ops func)
>>> +{
>>> + p4d_t *p4d;
>>> + pud_t *pud;
>>> + unsigned long next;
>>> + int ret;
>>> +
>>> + ret = 0;
>>> + p4d = p4d_offset(pgd, addr);
>>> + pud = pud_offset(p4d, addr);
>>> + do {
>>> + next = pud_addr_end(addr, end);
>>> + if (!pud_present(*pud))
>>> + continue;
>>> +
>>> + ret |= level2_ptw_pmd(pud, addr, next, func);
>>> + } while (pud++, addr = next, addr != end);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +static int level2_ptw_pgd(pgd_t *pgd, unsigned long addr, unsigned
>>> long end,
>>> + level2_pte_ops func)
>>> +{
>>> + unsigned long next;
>>> + int ret;
>>> +
>>> + ret = 0;
>>> + if (addr > end - 1)
>>> + return ret;
>>> + pgd = pgd + pgd_index(addr);
>>> + do {
>>> + next = pgd_addr_end(addr, end);
>>> + if (!pgd_present(*pgd))
>>> + continue;
>>> +
>>> + ret |= level2_ptw_pud(pgd, addr, next, func);
>>> + } while (pgd++, addr = next, addr != end);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +/*
>>> + * kvm_mkclean_gpa_pt() - Make a range of guest physical addresses
>>> clean.
>>> + * @kvm: KVM pointer.
>>> + * @start_gfn: Guest frame number of first page in GPA range to flush.
>>> + * @end_gfn: Guest frame number of last page in GPA range to flush.
>>> + *
>>> + * Make a range of GPA mappings clean so that guest writes will
>>> fault and
>>> + * trigger dirty page logging.
>>> + *
>>> + * The caller must hold the @kvm->mmu_lock spinlock.
>>> + *
>>> + * Returns: Whether any GPA mappings were modified, which would
>>> require
>>> + * derived mappings (GVA page tables & TLB enties) to be
>>> + * invalidated.
>>> + */
>>> +static int kvm_mkclean_gpa_pt(struct kvm *kvm, gfn_t start_gfn,
>>> gfn_t end_gfn)
>>> +{
>>> + return level2_ptw_pgd(kvm->arch.gpa_mm.pgd, start_gfn <<
>>> PAGE_SHIFT,
>>> + end_gfn << PAGE_SHIFT,
>>> level2_mkclean_pte);
>>> +}
>>> +
>>> +/*
>>> + * kvm_arch_mmu_enable_log_dirty_pt_masked() - write protect dirty
>>> pages
>>> + * @kvm: The KVM pointer
>>> + * @slot: The memory slot associated with mask
>>> + * @gfn_offset: The gfn offset in memory slot
>>> + * @mask: The mask of dirty pages at offset 'gfn_offset' in
>>> this memory
>>> + * slot to be write protected
>>> + *
>>> + * Walks bits set in mask write protects the associated pte's.
>>> Caller must
>>> + * acquire @kvm->mmu_lock.
>>> + */
>>> +void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
>>> + struct kvm_memory_slot *slot,
>>> + gfn_t gfn_offset, unsigned long mask)
>>> +{
>>> + gfn_t base_gfn = slot->base_gfn + gfn_offset;
>>> + gfn_t start = base_gfn + __ffs(mask);
>>> + gfn_t end = base_gfn + __fls(mask) + 1;
>>> +
>>> + kvm_mkclean_gpa_pt(kvm, start, end);
>>> +}
>>> +
>>> +void kvm_arch_commit_memory_region(struct kvm *kvm,
>>> + struct kvm_memory_slot *old,
>>> + const struct kvm_memory_slot *new,
>>> + enum kvm_mr_change change)
>>> +{
>>> + int needs_flush;
>>> +
>>> + /*
>>> + * If dirty page logging is enabled, write protect all pages
>>> in the slot
>>> + * ready for dirty logging.
>>> + *
>>> + * There is no need to do this in any of the following cases:
>>> + * CREATE: No dirty mappings will already exist.
>>> + * MOVE/DELETE: The old mappings will already have been
>>> cleaned up by
>>> + * kvm_arch_flush_shadow_memslot()
>>> + */
>>> + if (change == KVM_MR_FLAGS_ONLY &&
>>> + (!(old->flags & KVM_MEM_LOG_DIRTY_PAGES) &&
>>> + new->flags & KVM_MEM_LOG_DIRTY_PAGES)) {
>>> + spin_lock(&kvm->mmu_lock);
>>> + /* Write protect GPA page table entries */
>>> + needs_flush = kvm_mkclean_gpa_pt(kvm, new->base_gfn,
>>> + new->base_gfn + new->npages);
>>> + if (needs_flush)
>>> + kvm_flush_remote_tlbs(kvm);
>>> + spin_unlock(&kvm->mmu_lock);
>>> + }
>>> +}
>>> +
>>> +void kvm_arch_flush_shadow_all(struct kvm *kvm)
>>> +{
>>> + /* Flush whole GPA */
>>> + level2_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT);
>>> + /* Flush vpid for each vCPU individually */
>>> + kvm_flush_remote_tlbs(kvm);
>>> +}
>>> +
>>> +void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
>>> + struct kvm_memory_slot *slot)
>>> +{
>>> + int ret;
>>> +
>>> + /*
>>> + * The slot has been made invalid (ready for moving or
>>> deletion), so we
>>> + * need to ensure that it can no longer be accessed by any
>>> guest vCPUs.
>>> + */
>>> + spin_lock(&kvm->mmu_lock);
>>> + /* Flush slot from GPA */
>>> + ret = level2_flush_range(kvm, slot->base_gfn,
>>> + slot->base_gfn + slot->npages);
>>> + /* Let implementation do the rest */
>>> + if (ret)
>>> + kvm_flush_remote_tlbs(kvm);
>>> + spin_unlock(&kvm->mmu_lock);
>>> +}
>>> +
>>> +void _kvm_destroy_mm(struct kvm *kvm)
>>> +{
>>> + /* It should always be safe to remove after flushing the
>>> whole range */
>>> + level2_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT);
>>> + pgd_free(NULL, kvm->arch.gpa_mm.pgd);
>>> + kvm->arch.gpa_mm.pgd = NULL;
>>> +}
>>> +
>>> +/*
>>> + * Mark a range of guest physical address space old (all accesses
>>> fault) in the
>>> + * VM's GPA page table to allow detection of commonly used pages.
>>> + */
>>> +static int level2_mkold_pte(void *pte)
>>> +{
>>> + pte_t val;
>>> +
>>> + val = *(pte_t *)pte;
>>> + if (pte_young(val)) {
>>> + *(pte_t *)pte = pte_mkold(val);
>>> + return 1;
>>> + }
>>> + return 0;
>>> +}
>>> +
>>> +bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>>> +{
>>> + return level2_flush_range(kvm, range->start, range->end);
>>> +}
>>> +
>>> +bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>>> +{
>>> + gpa_t gpa = range->start << PAGE_SHIFT;
>>> + pte_t hva_pte = range->pte;
>>> + pte_t *ptep = kvm_pte_for_gpa(kvm, NULL, gpa);
>>> + pte_t old_pte;
>>> +
>>> + if (!ptep)
>>> + return false;
>>> +
>>> + /* Mapping may need adjusting depending on memslot flags */
>>> + old_pte = *ptep;
>>> + if (range->slot->flags & KVM_MEM_LOG_DIRTY_PAGES &&
>>> !pte_dirty(old_pte))
>>> + hva_pte = pte_mkclean(hva_pte);
>>> + else if (range->slot->flags & KVM_MEM_READONLY)
>>> + hva_pte = pte_wrprotect(hva_pte);
>>> +
>>> + set_pte(ptep, hva_pte);
>>> +
>>> + /* Replacing an absent or old page doesn't need flushes */
>>> + if (!pte_present(old_pte) || !pte_young(old_pte))
>>> + return false;
>>> +
>>> + /* Pages swapped, aged, moved, or cleaned require flushes */
>>> + return !pte_present(hva_pte) ||
>>> + !pte_young(hva_pte) ||
>>> + pte_pfn(old_pte) != pte_pfn(hva_pte) ||
>>> + (pte_dirty(old_pte) && !pte_dirty(hva_pte));
>>> +}
>>> +
>>> +bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>>> +{
>>> + return level2_ptw_pgd(kvm->arch.gpa_mm.pgd, range->start <<
>>> PAGE_SHIFT,
>>> + range->end << PAGE_SHIFT,
>>> level2_mkold_pte);
>>> +}
>>> +
>>> +bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>>> +{
>>> + gpa_t gpa = range->start << PAGE_SHIFT;
>>> + pte_t *ptep = kvm_pte_for_gpa(kvm, NULL, gpa);
>>> +
>>> + if (ptep && pte_present(*ptep) && pte_young(*ptep))
>>> + return true;
>>> +
>>> + return false;
>>> +}
>>> +
>>> +/**
>>> + * kvm_map_page_fast() - Fast path GPA fault handler.
>>> + * @vcpu: vCPU pointer.
>>> + * @gpa: Guest physical address of fault.
>>> + * @write: Whether the fault was due to a write.
>>> + *
>>> + * Perform fast path GPA fault handling, doing all that can be done
>>> without
>>> + * calling into KVM. This handles marking old pages young (for idle
>>> page
>>> + * tracking), and dirtying of clean pages (for dirty page logging).
>>> + *
>>> + * Returns: 0 on success, in which case we can update derived
>>> mappings and
>>> + * resume guest execution.
>>> + * -EFAULT on failure due to absent GPA mapping or
>>> write to
>>> + * read-only page, in which case KVM must be consulted.
>>> + */
>>> +static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa,
>>> + bool write)
>>> +{
>>> + struct kvm *kvm = vcpu->kvm;
>>> + gfn_t gfn = gpa >> PAGE_SHIFT;
>>> + pte_t *ptep;
>>> + kvm_pfn_t pfn = 0;
>>> + bool pfn_valid = false;
>>> + int ret = 0;
>>> +
>>> + spin_lock(&kvm->mmu_lock);
>>> +
>>> + /* Fast path - just check GPA page table for an existing
>>> entry */
>>> + ptep = kvm_pte_for_gpa(kvm, NULL, gpa);
>>> + if (!ptep || !pte_present(*ptep)) {
>>> + ret = -EFAULT;
>>> + goto out;
>>> + }
>>> +
>>> + /* Track access to pages marked old */
>>> + if (!pte_young(*ptep)) {
>>> + set_pte(ptep, pte_mkyoung(*ptep));
>>> + pfn = pte_pfn(*ptep);
>>> + pfn_valid = true;
>>> + /* call kvm_set_pfn_accessed() after unlock */
>>> + }
>>> + if (write && !pte_dirty(*ptep)) {
>>> + if (!pte_write(*ptep)) {
>>> + ret = -EFAULT;
>>> + goto out;
>>> + }
>>> +
>>> + /* Track dirtying of writeable pages */
>>> + set_pte(ptep, pte_mkdirty(*ptep));
>>> + pfn = pte_pfn(*ptep);
>>> + mark_page_dirty(kvm, gfn);
>>> + kvm_set_pfn_dirty(pfn);
>>> + }
>>> +
>>> +out:
>>> + spin_unlock(&kvm->mmu_lock);
>>> + if (pfn_valid)
>>> + kvm_set_pfn_accessed(pfn);
>>> + return ret;
>>> +}
>>> +
>>> +/**
>>> + * kvm_map_page() - Map a guest physical page.
>>> + * @vcpu: vCPU pointer.
>>> + * @gpa: Guest physical address of fault.
>>> + * @write: Whether the fault was due to a write.
>>> + *
>>> + * Handle GPA faults by creating a new GPA mapping (or updating an
>>> existing
>>> + * one).
>>> + *
>>> + * This takes care of marking pages young or dirty (idle/dirty page
>>> tracking),
>>> + * asking KVM for the corresponding PFN, and creating a mapping in
>>> the GPA page
>>> + * tables. Derived mappings (GVA page tables and TLBs) must be
>>> handled by the
>>> + * caller.
>>> + *
>>> + * Returns: 0 on success
>>> + * -EFAULT if there is no memory region at @gpa or a
>>> write was
>>> + * attempted to a read-only memory region. This is
>>> usually handled
>>> + * as an MMIO access.
>>> + */
>>> +static int kvm_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
>>> bool write)
>>> +{
>>> + bool writeable;
>>> + int srcu_idx, err = 0, retry_no = 0;
>>> + unsigned long hva;
>>> + unsigned long mmu_seq;
>>> + unsigned long prot_bits;
>>> + pte_t *ptep, new_pte;
>>> + kvm_pfn_t pfn;
>>> + gfn_t gfn = gpa >> PAGE_SHIFT;
>>> + struct vm_area_struct *vma;
>>> + struct kvm *kvm = vcpu->kvm;
>>> + struct kvm_memory_slot *memslot;
>>> + struct kvm_mmu_memory_cache *memcache =
>>> &vcpu->arch.mmu_page_cache;
>>> +
>>> + /* Try the fast path to handle old / clean pages */
>>> + srcu_idx = srcu_read_lock(&kvm->srcu);
>>> + err = kvm_map_page_fast(vcpu, gpa, write);
>>> + if (!err)
>>> + goto out;
>>> +
>>> + memslot = gfn_to_memslot(kvm, gfn);
>>> + hva = gfn_to_hva_memslot_prot(memslot, gfn, &writeable);
>>> + if (kvm_is_error_hva(hva) || (write && !writeable))
>>> + goto out;
>>> +
>>> + mmap_read_lock(current->mm);
>>> + vma = find_vma_intersection(current->mm, hva, hva + 1);
>>> + if (unlikely(!vma)) {
>>> + kvm_err("Failed to find VMA for hva 0x%lx\n", hva);
>>> + mmap_read_unlock(current->mm);
>>> + err = -EFAULT;
>>> + goto out;
>>> + }
>>> + mmap_read_unlock(current->mm);
>>> +
>>> + /* We need a minimum of cached pages ready for page table
>>> creation */
>>> + err = kvm_mmu_topup_memory_cache(memcache,
>>> KVM_MMU_CACHE_MIN_PAGES);
>>> + if (err)
>>> + goto out;
>>> +
>>> +retry:
>>> + /*
>>> + * Used to check for invalidations in progress, of the pfn
>>> that is
>>> + * returned by pfn_to_pfn_prot below.
>>> + */
>>> + mmu_seq = kvm->mmu_invalidate_seq;
>>> + /*
>>> + * Ensure the read of mmu_invalidate_seq isn't reordered
>>> with PTE reads in
>>> + * gfn_to_pfn_prot() (which calls get_user_pages()), so that
>>> we don't
>>> + * risk the page we get a reference to getting unmapped
>>> before we have a
>>> + * chance to grab the mmu_lock without
>>> mmu_invalidate_retry() noticing.
>>> + *
>>> + * This smp_rmb() pairs with the effective smp_wmb() of the
>>> combination
>>> + * of the pte_unmap_unlock() after the PTE is zapped, and the
>>> + * spin_lock() in
>>> kvm_mmu_invalidate_invalidate_<page|range_end>() before
>>> + * mmu_invalidate_seq is incremented.
>>> + */
>>> + smp_rmb();
>>> +
>>> + /* Slow path - ask KVM core whether we can access this GPA */
>>> + pfn = gfn_to_pfn_prot(kvm, gfn, write, &writeable);
>>> + if (is_error_noslot_pfn(pfn)) {
>>> + err = -EFAULT;
>>> + goto out;
>>> + }
>>> +
>>> + spin_lock(&kvm->mmu_lock);
>>> + /* Check if an invalidation has taken place since we got pfn */
>>> + if (mmu_invalidate_retry(kvm, mmu_seq)) {
>>> + /*
>>> + * This can happen when mappings are changed
>>> asynchronously, but
>>> + * also synchronously if a COW is triggered by
>>> + * gfn_to_pfn_prot().
>>> + */
>>> + spin_unlock(&kvm->mmu_lock);
>>> + kvm_set_pfn_accessed(pfn);
>>> + kvm_release_pfn_clean(pfn);
>>> + if (retry_no > 100) {
>>> + retry_no = 0;
>>> + schedule();
>>> + }
>>> + retry_no++;
>>> + goto retry;
>>> + }
>>> +
>>> + /*
>>> + * For emulated devices such virtio device, actual cache
>>> attribute is
>>> + * determined by physical machine.
>>> + * For pass through physical device, it should be uncachable
>>> + */
>>> + prot_bits = _PAGE_PRESENT | __READABLE;
>>> + if (vma->vm_flags & (VM_IO | VM_PFNMAP))
>>> + prot_bits |= _CACHE_SUC;
>>> + else
>>> + prot_bits |= _CACHE_CC;
>>> +
>>> + if (writeable) {
>>> + prot_bits |= _PAGE_WRITE;
>>> + if (write) {
>>> + prot_bits |= __WRITEABLE;
>>> + mark_page_dirty(kvm, gfn);
>>> + kvm_set_pfn_dirty(pfn);
>>> + }
>>> + }
>>> +
>>> + /* Ensure page tables are allocated */
>>> + ptep = kvm_pte_for_gpa(kvm, memcache, gpa);
>>> + new_pte = pfn_pte(pfn, __pgprot(prot_bits));
>>> + set_pte(ptep, new_pte);
>>> +
>>> + err = 0;
>>> + spin_unlock(&kvm->mmu_lock);
>>> + kvm_release_pfn_clean(pfn);
>>> + kvm_set_pfn_accessed(pfn);
>>> +out:
>>> + srcu_read_unlock(&kvm->srcu, srcu_idx);
>>> + return err;
>>> +}
>>> +
>>> +int kvm_handle_mm_fault(struct kvm_vcpu *vcpu, unsigned long gpa,
>>> bool write)
>>> +{
>>> + int ret;
>>> +
>>> + ret = kvm_map_page(vcpu, gpa, write);
>>> + if (ret)
>>> + return ret;
>>> +
>>> + /* Invalidate this entry in the TLB */
>>> + return kvm_flush_tlb_gpa(vcpu, gpa);
>>> +}
>>> +
>>> +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct
>>> kvm_memory_slot *memslot)
>>> +{
>>> +
>>> +}
>>> +
>>> +int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>> + const struct kvm_memory_slot *old,
>>> + struct kvm_memory_slot *new,
>>> + enum kvm_mr_change change)
>>> +{
>>> + return 0;
>>> +}
>>> +
>>> +void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
>>> + const struct kvm_memory_slot
>>> *memslot)
>>> +{
>>> + kvm_flush_remote_tlbs(kvm);
>>> +}
>>> --
>>> 2.39.1
>>>
>>>
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