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[v2,21/45] KVM: x86: Remove spurious clearing of async #PF MSR

Message ID 20191218215530.2280-22-sean.j.christopherson@intel.com
State Not Applicable
Headers show
Series KVM: Refactor vCPU creation | expand

Commit Message

Sean Christopherson Dec. 18, 2019, 9:55 p.m. UTC 
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>
---
 arch/x86/kvm/x86.c | 2 --
 1 file changed, 2 deletions(-)
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Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 19c14b786255..46626b52a4da 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9176,8 +9176,6 @@  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);
 }