From 5d49f08c2e08c1f0de1bb0f2e1307ec969451729 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Fri, 29 Apr 2022 01:04:16 +0000
Subject: [PATCH] KVM: x86/mmu: Shove refcounted page dependency into
host_pfn_mapping_level()
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>
---
arch/x86/kvm/mmu/mmu.c | 14 +++++++++++---
arch/x86/kvm/mmu/tdp_mmu.c | 4 ----
2 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 7ebb97c95da7d..27b2a56034961 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -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 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
* 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);
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 1e777b739ac4d..1ea40809ef1f3 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -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);
--
GitLab