openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior 

In record_steal_time(), st->preempted is read twice, and
trace_kvm_pv_tlb_flush() might output result inconsistent if
kvm_vcpu_flush_tlb_guest() see a different st->preempted later.

It is a very trivial problem and hardly has actual harm and can be
avoided by reseting and reading st->preempted in atomic way via xchg().

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>

Message-Id: <20210531174628.10265-1-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Lai Jiangshan 2021-06-01 01:46:28 +08:00 committed by Paolo Bonzini
parent b1bd5cba33
commit af3511ff7f
1 changed files with 4 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/kvm/x86.c
View File

@ -3101,9 +3101,11 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
* expensive IPIs.
*/
if (guest_pv_has(vcpu, KVM_FEATURE_PV_TLB_FLUSH)) {
u8 st_preempted = xchg(&st->preempted, 0);
trace_kvm_pv_tlb_flush(vcpu->vcpu_id,
st->preempted & KVM_VCPU_FLUSH_TLB);
if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB)
st_preempted & KVM_VCPU_FLUSH_TLB);
if (st_preempted & KVM_VCPU_FLUSH_TLB)
kvm_vcpu_flush_tlb_guest(vcpu);
} else {
st->preempted = 0;