Give kvm_run.exit_reason a defined initial value on entry into KVM_RUN:
other architectures (riscv, arm64) already use KVM_EXIT_UNKNOWN for this
purpose, so copy that convention.
This gives vCPUs trying to fill the run struct a mechanism to avoid
overwriting already-populated data, albeit an imperfect one. Being able
to detect an already-populated KVM run struct will prevent at least some
bugs in the upcoming implementation of KVM_CAP_MEMORY_FAULT_INFO, which
will attempt to fill the run struct whenever a vCPU fails a guest memory
access.
Without the already-populated check, KVM_CAP_MEMORY_FAULT_INFO could
change kvm_run in any code paths which
1. Populate kvm_run for some exit and prepare to return to userspace
2. Access guest memory for some reason (but without returning -EFAULTs
to userspace)
3. Finish the return to userspace set up in (1), now with the contents
of kvm_run changed to contain efault info.
Signed-off-by: Anish Moorthy <amoorthy@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ceb7c5e9cf9e..a7725d41570a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11163,6 +11163,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
if (r <= 0)
goto out;
+ kvm_run->exit_reason = KVM_EXIT_UNKNOWN;
r = vcpu_run(vcpu);
out:
--
2.41.0.rc0.172.g3f132b7071-goog
