On Wed, Aug 27, 2025, Binbin Wu wrote:
> On 8/21/2025 12:29 PM, Sagi Shahar wrote:
> > @@ -46,11 +69,23 @@ void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
> > {
> > struct kvm_run *run = vcpu->run;
> > - if (run->exit_reason == KVM_EXIT_IO && run->io.port == UCALL_PIO_PORT) {
> > - struct kvm_regs regs;
> > + switch (vm_type) {
> > + case KVM_X86_TDX_VM:
> > + if (vcpu->run->exit_reason == KVM_EXIT_MMIO &&
> > + vcpu->run->mmio.phys_addr == host_ucall_mmio_gpa &&
> > + vcpu->run->mmio.len == 8 && vcpu->run->mmio.is_write) {
> > + uint64_t data = *(uint64_t *)vcpu->run->mmio.data;
> > +
> > + return (void *)data;
> > + }
> > + return NULL;
>
> My first thought was how did SEV_ES or SNP work for this since they are not
> able to get RDI neither.
> Then I had a check in sev_smoke_test.c, both guest_sev_es_code() and
> guest_snp_code() call GUEST_ASSERT(), which finally calls ucall_assert(), but
> in test_sev(), the code doesn't handle ucall for SEV_ES or SNP.
> Does it mean GUEST_ASSERT() is currently not working and ignored for SEV_ES
> and SNP? Or did I miss anything?
GUEST_ASSERT() "works" for -ES and -SNP in the sense that it generates as test
failure due to the #VC not being handled (leads to SHUTDOWN). But you're correct
that ucall isn't functional yet. x86/sev_smoke_test.c fudges around lack of ucall
by using the GHCB MSR protocol to signal "done".
/*
* TODO: Add GHCB and ucall support for SEV-ES guests. For now, simply
* force "termination" to signal "done" via the GHCB MSR protocol.
*/
wrmsr(MSR_AMD64_SEV_ES_GHCB, GHCB_MSR_TERM_REQ);
vmgexit();
