[PATCH 03/12] KVM: x86: do not deliver asynchronous page faults if CR0.PG=0

Paolo Bonzini
2022-02-09T17:01:46Z

Enabling async page faults is nonsensical if paging is disabled, but
it is allowed because CR0.PG=0 does not clear the async page fault
MSR. Just ignore them and only use the artificial halt state,
similar to what happens in guest mode if async #PF vmexits are disabled.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/x86.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5e1298aef9e2..98aca0f2af12 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12272,7 +12272,9 @@ static inline bool apf_pageready_slot_free(struct kvm_vcpu *vcpu)

static bool kvm_can_deliver_async_pf(struct kvm_vcpu *vcpu)
{
- if (!vcpu->arch.apf.delivery_as_pf_vmexit && is_guest_mode(vcpu))
+ if (is_guest_mode(vcpu)
+ ? !vcpu->arch.apf.delivery_as_pf_vmexit
+ : !is_cr0_pg(vcpu->arch.mmu))
return false;

if (!kvm_pv_async_pf_enabled(vcpu) ||
--
2.31.1