[PATCH] KVM: x86/mmu: Block all page faults during kvm_zap_gfn_range()

[PATCH] KVM: x86/mmu: Block all page faults during kvm_zap_gfn_range()

[Sean Christopherson]

When zapping a GFN range, pass 0 => ALL_ONES for the to-be-invalidated
range to effectively block all page faults while the zap is in-progress.
The invalidation helpers take a host virtual address, whereas zapping a
GFN obviously provides a guest physical address and with the wrong unit
of measurement (frame vs. byte).

Alternatively, KVM could walk all memslots to get the associated HVAs,
but thanks to SMM, that would require multiple lookups.  And practically
speaking, kvm_zap_gfn_range() usage is quite rare and not a hot path,
e.g. MTRR and CR0.CD are almost guaranteed to be done only on vCPU0
during boot, and APICv inhibits are similarly infrequent operations.

Fixes: edb298c663fc ("KVM: x86/mmu: bump mmu notifier count in kvm_zap_gfn_range")
Reported-by: Chao Peng <chao.p.peng@linux.intel.com>
Cc: stable@vger.kernel.org
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 93c389eaf471..f14efcaebec3 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6098,7 +6098,7 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
 
 	write_lock(&kvm->mmu_lock);
 
-	kvm_mmu_invalidate_begin(kvm, gfn_start, gfn_end);
+	kvm_mmu_invalidate_begin(kvm, 0, -1ul);
 
 	flush = kvm_rmap_zap_gfn_range(kvm, gfn_start, gfn_end);
 
@@ -6112,7 +6112,7 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
 		kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
 						   gfn_end - gfn_start);
 
-	kvm_mmu_invalidate_end(kvm, gfn_start, gfn_end);
+	kvm_mmu_invalidate_end(kvm, 0, -1ul);
 
 	write_unlock(&kvm->mmu_lock);
 }

base-commit: d663b8a285986072428a6a145e5994bc275df994
-- 
2.38.1.431.g37b22c650d-goog

Re: [PATCH] KVM: x86/mmu: Block all page faults during kvm_zap_gfn_range()

[Paolo Bonzini]

Queued, thanks.

Paolo