[PATCH v2 4/6] KVM: x86/mmu: Fix wrong start gfn of tlb flushing with range

Hou Wenlong
2022-08-24T09:29:56Z

When a spte is dropped, the start gfn of tlb flushing should
be the gfn of spte not the base gfn of SP which contains the
spte. Also introduce a helper function to do range-based
flushing when a spte is dropped, which would help prevent
future buggy use of kvm_flush_remote_tlbs_with_address() in
such case.

Fixes: c3134ce240eed ("KVM: Replace old tlb flush function with new one to flush a specified range.")
Suggested-by: David Matlack <dmatlack@google.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
---
arch/x86/kvm/mmu/mmu.c | 20 +++++++++++++++-----
arch/x86/kvm/mmu/paging_tmpl.h | 3 +--
2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 3bcff56df109..e0b9432b9491 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -260,6 +260,18 @@ void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
kvm_flush_remote_tlbs_with_range(kvm, &range);
}

+static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index);
+
+/* Flush the range of guest memory mapped by the given SPTE. */
+static void kvm_flush_remote_tlbs_sptep(struct kvm *kvm, u64 *sptep)
+{
+ struct kvm_mmu_page *sp = sptep_to_sp(sptep);
+ gfn_t gfn = kvm_mmu_page_get_gfn(sp, spte_index(sptep));
+
+ kvm_flush_remote_tlbs_with_address(kvm, gfn,
+ KVM_PAGES_PER_HPAGE(sp->role.level));
+}
+
/* Flush all memory mapped by the given direct SP. */
static void kvm_flush_remote_tlbs_direct_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
{
@@ -1156,8 +1168,7 @@ static void drop_large_spte(struct kvm *kvm, u64 *sptep, bool flush)
drop_spte(kvm, sptep);

if (flush)
- kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
- KVM_PAGES_PER_HPAGE(sp->role.level));
+ kvm_flush_remote_tlbs_sptep(kvm, sptep);
}

/*
@@ -1608,7 +1619,7 @@ static void __rmap_add(struct kvm *kvm,
if (rmap_count > RMAP_RECYCLE_THRESHOLD) {
kvm_zap_all_rmap_sptes(kvm, rmap_head);
kvm_flush_remote_tlbs_with_address(
- kvm, sp->gfn, KVM_PAGES_PER_HPAGE(sp->role.level));
+ kvm, gfn, KVM_PAGES_PER_HPAGE(sp->role.level));
}
}

@@ -6402,8 +6413,7 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
kvm_zap_one_rmap_spte(kvm, rmap_head, sptep);

if (kvm_available_flush_tlb_with_range())
- kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
- KVM_PAGES_PER_HPAGE(sp->role.level));
+ kvm_flush_remote_tlbs_sptep(kvm, sptep);
else
need_tlb_flush = 1;

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 39e0205e7300..04149c704d5b 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -937,8 +937,7 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa)

mmu_page_zap_pte(vcpu->kvm, sp, sptep, NULL);
if (is_shadow_present_pte(old_spte))
- kvm_flush_remote_tlbs_with_address(vcpu->kvm,
- sp->gfn, KVM_PAGES_PER_HPAGE(sp->role.level));
+ kvm_flush_remote_tlbs_sptep(vcpu->kvm, sptep);

if (!rmap_can_add(vcpu))
break;
--
2.31.1