On Mon, Feb 23, 2026, Tycho Andersen wrote: > > > + /* > > > + * In some cases when SEV-SNP is enabled, firmware disallows starting > > > + * an SEV-ES VM. When SEV-SNP is enabled try to launch an SEV-ES, and > > > + * check the underlying firmware error for this case. > > > + */ > > > + vm = vm_sev_create_with_one_vcpu(KVM_X86_SEV_ES_VM, guest_sev_es_code, > > > + &vcpu); > > > > If there's a legimate reason why an SEV-ES VM can't be created, then that > > needs > > to be explicitly enumerated in some way by the kernel. E.g. is this due to > > lack > > of ASIDs due to CipherTextHiding or something? > > Newer firmware that fixes CVE-2025-48514 won't allow SEV-ES VMs to be > started with SNP enabled, there is a footnote (2) about it here: > > https://www.amd.com/en/resources/product-security/bulletin/amd-sb-3023.html > > Probably should have included this in the patch, sorry. > > > Throwing a noodle to see if it sticks is not an option. > > Sure, we could do some firmware version test to see if it's fixed > instead? Or do this same test in the kernel and export that as an > ioctl?
Uh, no idea what would be ideal, but there absolutely needs to be some way to communicate lack of effective SEV-ES support to userspace, and in a way that doesn't break userspace. Hrm, I think we also neglected to communicate when SEV and SEV-ES are effectively unusable, e.g. due to CipherTextHiding, so maybe we can kill two birds with one stone? IIRC, we didn't bother enumerating the limitation with CipherTextHiding because making SEV-ES unusable would require a deliberate act from the admin. "Update firmware" is also an deliberate act, but the side effect of SEV-ES being disabled, not so much.
