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KVM: x86: Drop superfluous caching of KVM_ASYNC_PF_SEND_ALWAYS

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Drop kvm_vcpu_arch.apf.send_always 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 send_always 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 send_always when PV
APF support is disabled.

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

Opportunistically turn the enabled vs. disabled logic at the end of
kvm_pv_enable_async_pf() into an if-else instead of using an early return,
e.g. so that it's more obvious that both paths are "success" paths.

Fixes: 6adba52742 ("KVM: Let host know whether the guest can handle async PF in non-userspace context.")
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://patch.msgid.link/20260406225359.1245490-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-04-06 15:53:58 -07:00
parent 3c0bf11dd4
commit 7e985021ef
2 changed files with 4 additions and 9 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -1057,7 +1057,6 @@ struct kvm_vcpu_arch {
u16 vec;
u32 id;
u32 host_apf_flags;
bool send_always;
bool pageready_pending;
} apf;

12
arch/x86/kvm/x86.c
View File

@ -3660,16 +3660,12 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
vcpu->arch.apf.msr_en_val = data;
if (!__kvm_pv_async_pf_enabled(data)) {
if (__kvm_pv_async_pf_enabled(data)) {
kvm_async_pf_wakeup_all(vcpu);
} else {
kvm_clear_async_pf_completion_queue(vcpu);
kvm_async_pf_hash_reset(vcpu);
return 0;
}
vcpu->arch.apf.send_always = (data & KVM_ASYNC_PF_SEND_ALWAYS);
kvm_async_pf_wakeup_all(vcpu);
return 0;
}
@ -14008,7 +14004,7 @@ static bool kvm_can_deliver_async_pf(struct kvm_vcpu *vcpu)
if (!kvm_pv_async_pf_enabled(vcpu))
return false;
if (!vcpu->arch.apf.send_always &&
if (!(vcpu->arch.apf.msr_en_val & KVM_ASYNC_PF_SEND_ALWAYS) &&
(vcpu->arch.guest_state_protected || !kvm_x86_call(get_cpl)(vcpu)))
return false;