On Fri, Jun 02, 2023 at 04:19:07PM +0000, Anish Moorthy <amoorthy@xxxxxxxxxx> wrote: > 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. > As vmx code uses KVM_EXIT_UNKNOWN with hardware_exit_reason=exit reason, Can we initialize hardware_exit_reason to -1. It's just in case. > 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; + kvm_run->hardware_exit_reason = -1; /* unused exit reason value */ > r = vcpu_run(vcpu); > > out: > -- > 2.41.0.rc0.172.g3f132b7071-goog > -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
