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authorLai Jiangshan <laijs@linux.alibaba.com>2021-09-18 08:56:27 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2021-09-23 10:28:44 -0400
commitf81602958c115fc7c87b985f71574042a20ff858 (patch)
treed907a04c9aa0fe43ecafcdf0a6f008566b3987cc
parentfaf6b755629627f19feafa75b32e81cd7738f12d (diff)
KVM: X86: Fix missed remote tlb flush in rmap_write_protect()
When kvm->tlbs_dirty > 0, some rmaps might have been deleted without flushing tlb remotely after kvm_sync_page(). If @gfn was writable before and it's rmaps was deleted in kvm_sync_page(), and if the tlb entry is still in a remote running VCPU, the @gfn is not safely protected. To fix the problem, kvm_sync_page() does the remote flush when needed to avoid the problem. Fixes: a4ee1ca4a36e ("KVM: MMU: delay flush all tlbs on sync_page path") Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-2-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/mmu/paging_tmpl.h23
1 files changed, 2 insertions, 21 deletions
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 7d03e9b7ccfa..efce0a935e23 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -1047,14 +1047,6 @@ static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gpa_t vaddr,
* Using the cached information from sp->gfns is safe because:
* - The spte has a reference to the struct page, so the pfn for a given gfn
* can't change unless all sptes pointing to it are nuked first.
- *
- * Note:
- * We should flush all tlbs if spte is dropped even though guest is
- * responsible for it. Since if we don't, kvm_mmu_notifier_invalidate_page
- * and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't
- * used by guest then tlbs are not flushed, so guest is allowed to access the
- * freed pages.
- * And we increase kvm->tlbs_dirty to delay tlbs flush in this case.
*/
static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
@@ -1107,13 +1099,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
return 0;
if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) {
- /*
- * Update spte before increasing tlbs_dirty to make
- * sure no tlb flush is lost after spte is zapped; see
- * the comments in kvm_flush_remote_tlbs().
- */
- smp_wmb();
- vcpu->kvm->tlbs_dirty++;
+ set_spte_ret |= SET_SPTE_NEED_REMOTE_TLB_FLUSH;
continue;
}
@@ -1128,12 +1114,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
if (gfn != sp->gfns[i]) {
drop_spte(vcpu->kvm, &sp->spt[i]);
- /*
- * The same as above where we are doing
- * prefetch_invalid_gpte().
- */
- smp_wmb();
- vcpu->kvm->tlbs_dirty++;
+ set_spte_ret |= SET_SPTE_NEED_REMOTE_TLB_FLUSH;
continue;
}

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