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KVM: x86: Remove spurious clearing of async #PF MSR

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Remove a bogus clearing of apf.msr_val from kvm_arch_vcpu_destroy().

apf.msr_val is only set to a non-zero value by kvm_pv_enable_async_pf(),
which is only reachable by kvm_set_msr_common(), i.e. by writing
MSR_KVM_ASYNC_PF_EN.  KVM does not autonomously write said MSR, i.e.
can only be written via KVM_SET_MSRS or KVM_RUN.  Since KVM_SET_MSRS and
KVM_RUN are vcpu ioctls, they require a valid vcpu file descriptor.
kvm_arch_vcpu_destroy() is only called if KVM_CREATE_VCPU fails, and KVM
declares KVM_CREATE_VCPU successful once the vcpu fd is installed and
thus visible to userspace.  Ergo, apf.msr_val cannot be non-zero when
kvm_arch_vcpu_destroy() is called.

Fixes: 344d9588a9df0 ("KVM: Add PV MSR to enable asynchronous page faults delivery.")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-12-18 13:55:06 -08:00 committed by Paolo Bonzini
parent 9d979c7e6f
commit 208050dac5
1 changed files with 0 additions and 2 deletions
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2
arch/x86/kvm/x86.c
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@ -9257,8 +9257,6 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
{
vcpu->arch.apf.msr_val = 0;
kvm_arch_vcpu_free(vcpu);
}