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KVM: x86/mmu: Shove refcounted page dependency into host_pfn_mapping_level()

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Move the check that restricts mapping huge pages into the guest to pfns
that are backed by refcounted 'struct page' memory into the helper that
actually "requires" a 'struct page', host_pfn_mapping_level().  In
addition to deduplicating code, moving the check to the helper eliminates
the subtle requirement that the caller check that the incoming pfn is
backed by a refcounted struct page, and as an added bonus avoids an extra
pfn_to_page() lookup.

Note, the is_error_noslot_pfn() check in kvm_mmu_hugepage_adjust() needs
to stay where it is, as it guards against dereferencing a NULL memslot in
the kvm_slot_dirty_track_enabled() that follows.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220429010416.2788472-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-04-29 01:04:16 +00:00 • committed by Paolo Bonzini
parent b14b2690c5
commit 5d49f08c2e
2 changed files with 11 additions and 7 deletions
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14
arch/x86/kvm/mmu/mmu.c
View file

@ -2791,8 +2791,8 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
const struct kvm_memory_slot *slot)
{
struct page *page = pfn_to_page(pfn);
int level = PG_LEVEL_4K;
struct page *page;
unsigned long hva;
unsigned long flags;
pgd_t pgd;
@ -2800,6 +2800,14 @@ static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
pud_t pud;
pmd_t pmd;
/*
* Note, @slot must be non-NULL, i.e. the caller is responsible for
* ensuring @pfn isn't garbage and is backed by a memslot.
*/
page = kvm_pfn_to_refcounted_page(pfn);
if (!page)
return PG_LEVEL_4K;
if (!PageCompound(page) && !kvm_is_zone_device_page(page))
return PG_LEVEL_4K;
@ -2884,7 +2892,7 @@ void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
if (unlikely(fault->max_level == PG_LEVEL_4K))
return;
if (is_error_noslot_pfn(fault->pfn) || !kvm_pfn_to_refcounted_page(fault->pfn))
if (is_error_noslot_pfn(fault->pfn))
return;
if (kvm_slot_dirty_track_enabled(slot))
@ -5996,7 +6004,7 @@ restart:
* the guest, and the guest page table is using 4K page size
* mapping if the indirect sp has level = 1.
*/
if (sp->role.direct && kvm_pfn_to_refcounted_page(pfn) &&
if (sp->role.direct &&
sp->role.level < kvm_mmu_max_mapping_level(kvm, slot, sp->gfn,
pfn, PG_LEVEL_NUM)) {
pte_list_remove(kvm, rmap_head, sptep);

4
arch/x86/kvm/mmu/tdp_mmu.c
View file

@ -1750,10 +1750,6 @@ static void zap_collapsible_spte_range(struct kvm *kvm,
* be mapped at a higher level.
*/
pfn = spte_to_pfn(iter.old_spte);
if (!kvm_pfn_to_refcounted_page(pfn))
continue;
max_mapping_level = kvm_mmu_max_mapping_level(kvm, slot,
iter.gfn, pfn, PG_LEVEL_NUM);