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KVM: x86: Drop superfluous caching of KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT

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Drop kvm_vcpu_arch.apf.delivery_as_pf_vmexit and instead use msr_en_val as
the source of truth to reduce the probability of operating on stale data.
This fixes flaws where KVM fails to update delivery_as_pf_vmexit when APF
is explicitly disabled by the guest or implicitly disabled by KVM on INIT.
Absent other bugs, the flaws are benign as KVM *shouldn't* consume
delivery_as_pf_vmexit when PV APF support is disabled.

Simply delete the field, as there's zero benefit to maintaining a separate
"cache" of the state.

Fixes: 52a5c155cf ("KVM: async_pf: Let guest support delivery of async_pf from guest mode")
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://patch.msgid.link/20260406225359.1245490-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-04-06 15:53:57 -07:00
parent 923ca078f0
commit 3c0bf11dd4
2 changed files with 1 additions and 3 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -1058,7 +1058,6 @@ struct kvm_vcpu_arch {
u32 id;
u32 host_apf_flags;
bool send_always;
bool delivery_as_pf_vmexit;
bool pageready_pending;
} apf;

3
arch/x86/kvm/x86.c
View File

@ -3667,7 +3667,6 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
}
vcpu->arch.apf.send_always = (data & KVM_ASYNC_PF_SEND_ALWAYS);
vcpu->arch.apf.delivery_as_pf_vmexit = data & KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
kvm_async_pf_wakeup_all(vcpu);
@ -14018,7 +14017,7 @@ static bool kvm_can_deliver_async_pf(struct kvm_vcpu *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;
return vcpu->arch.apf.msr_en_val & KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
} else {
/*
* Play it safe in case the guest temporarily disables paging.