[PATCH v2 26/43] KVM: VMX: Read Posted Interrupt "control" exactly once per loop iteration
From: Sean Christopherson <seanjc@google.com>
Date: 2021-10-09 02:15:34
Also in:
kvm-riscv, kvmarm, linux-arm-kernel, linux-mips, linux-riscv, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Use READ_ONCE() when loading the posted interrupt descriptor control
field to ensure "old" and "new" have the same base value. If the
compiler emits separate loads, and loads into "new" before "old", KVM
could theoretically drop the ON bit if it were set between the loads.
Fixes: 28b835d60fcc ("KVM: Update Posted-Interrupts Descriptor when vCPU is preempted")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/posted_intr.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index 414ea6972b5c..fea343dcc011 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c@@ -53,7 +53,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) /* The full case. */ do { - old.control = new.control = pi_desc->control; + old.control = new.control = READ_ONCE(pi_desc->control); dest = cpu_physical_id(cpu);
@@ -104,7 +104,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) "Wakeup handler not enabled while the vCPU was blocking"); do { - old.control = new.control = pi_desc->control; + old.control = new.control = READ_ONCE(pi_desc->control); dest = cpu_physical_id(vcpu->cpu);
@@ -160,7 +160,7 @@ int pi_pre_block(struct kvm_vcpu *vcpu) "Posted Interrupt Suppress Notification set before blocking"); do { - old.control = new.control = pi_desc->control; + old.control = new.control = READ_ONCE(pi_desc->control); /* set 'NV' to 'wakeup vector' */ new.nv = POSTED_INTR_WAKEUP_VECTOR;
--
2.33.0.882.g93a45727a2-goog