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KVM: x86: do not deliver asynchronous page faults if CR0.PG=0 

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.

Given the increasingly complex logic, and the nicer code if the new
"if" is placed last, opportunistically change the "||" into a chain
of "if (...) return false" statements.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2022-02-09 05:17:38 -05:00
parent d617429936
commit 57cb3bb0dc
1 changed files with 18 additions and 4 deletions
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22
arch/x86/kvm/x86.c
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@ -12287,14 +12287,28 @@ 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 (!kvm_pv_async_pf_enabled(vcpu))
return false;
if (!kvm_pv_async_pf_enabled(vcpu) ||
(vcpu->arch.apf.send_user_only && static_call(kvm_x86_get_cpl)(vcpu) == 0))
if (vcpu->arch.apf.send_user_only &&
static_call(kvm_x86_get_cpl)(vcpu) == 0)
return false;
return true;
if (is_guest_mode(vcpu)) {
/*
* L1 needs to opt into the special #PF vmexits that are
* used to deliver async page faults.
*/
return vcpu->arch.apf.delivery_as_pf_vmexit;
} else {
/*
* Play it safe in case the guest temporarily disables paging.
* The real mode IDT in particular is unlikely to have a #PF
* exception setup.
*/
return is_paging(vcpu);
}
}
bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu)