diff options
| author | Andrew Jones <drjones@redhat.com> | 2017-04-26 22:32:24 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2017-04-27 14:16:17 +0200 |
| commit | cde9af6e79046e12cd08d161139b1d5e57e9fbac (patch) | |
| tree | 2192140fe822f0805d3b766f3e277798e12445b0 /arch/x86/kvm | |
| parent | 6c6e8360b34d59d2f687a1649e61173742dbc891 (diff) | |
KVM: add explicit barrier to kvm_vcpu_kick
kvm_vcpu_kick() must issue a general memory barrier prior to reading
vcpu->mode in order to ensure correctness of the mutual-exclusion
memory barrier pattern used with vcpu->requests. While the cmpxchg
called from kvm_vcpu_kick():
kvm_vcpu_kick
kvm_arch_vcpu_should_kick
kvm_vcpu_exiting_guest_mode
cmpxchg
implies general memory barriers before and after the operation, that
implication is only valid when cmpxchg succeeds. We need an explicit
barrier for when it fails, otherwise a VCPU thread on its entry path
that reads zero for vcpu->requests does not exclude the possibility
the requesting thread sees !IN_GUEST_MODE when it reads vcpu->mode.
kvm_make_all_cpus_request already had a barrier, so we remove it, as
now it would be redundant.
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/x86.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0936c3e2e51c..69fcee26f4da 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6853,7 +6853,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) /* * 1) We should set ->mode before checking ->requests. Please see - * the comment in kvm_make_all_cpus_request. + * the comment in kvm_vcpu_exiting_guest_mode(). * * 2) For APICv, we should set ->mode before checking PIR.ON. This * pairs with the memory barrier implicit in pi_test_and_set_on |