On Wed, Jul 30, 2025 at 10:07:36AM +0800, Xiaoyao Li wrote:
> On 7/30/2025 3:33 AM, Sean Christopherson wrote:
> > Exit to userspace with -EFAULT and a valid MEMORY_FAULT exit if a vCPU
> > hits an unexpected pending S-EPT Violation instead of marking the VM dead.
> > While it's unlikely the VM can continue on, whether or not to terminate
> > the VM is not KVM's decision to make.
> >
> > Set memory_fault.size to zero to communicate to userspace that reported
> > fault is "bad", and to effectively terminate the VM if userspace blindly
> > treats the exit as a conversion attempt (KVM_SET_MEMORY_ATTRIBUTES will
> > fail with -EINVAL if the size is zero).
>
> This sets a special contract on size zero.
+1.
Or would it be good to use pr_warn_once() to indicate that the VM termination
reason is "Guest access before accepting" if a new exit type is not specified?
This info is straightforward and helpful in cases when a TD is accidentally
killed.
> I had a patch internally, which introduce a new exit type:
>
> + /* KVM_EXIT_GUEST_ERROR */
> + struct {
> + #define KVM_GUEST_ERROR_TDX_ACCESS_PENDING_PAGE 0
> + __u32 error_type;
> + __u32 ndata;
> + __u64 data[16];
> + } guest_error;
>
> how about it?
>
> > Opportunistically delete the pr_warn(), which could be abused to spam the
> > kernel log, and is largely useless outside of interact debug as it doesn't
> > specify which VM encountered a failure.
> >
> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/vmx/tdx.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> > index 3e0d4edee849..c2ef03f39c32 100644
> > --- a/arch/x86/kvm/vmx/tdx.c
> > +++ b/arch/x86/kvm/vmx/tdx.c
> > @@ -1937,10 +1937,8 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
> > if (vt_is_tdx_private_gpa(vcpu->kvm, gpa)) {
> > if (tdx_is_sept_violation_unexpected_pending(vcpu)) {
> > - pr_warn("Guest access before accepting 0x%llx on vCPU %d\n",
> > - gpa, vcpu->vcpu_id);
> > - kvm_vm_dead(vcpu->kvm);
> > - return -EIO;
> > + kvm_prepare_memory_fault_exit(vcpu, gpa, 0, true, false, true);
> > + return -EFAULT;
> > }
> > /*
> > * Always treat SEPT violations as write faults. Ignore the
>
>
