Re: [PATCH v15 29/41] KVM: SEV: Synchronize MSR_IA32_XSS from the GHCB when it's valid

Edgecombe, Rick P
2025-09-18T21:42:26Z

On Thu, 2025-09-18 at 16:23 -0500, John Allen wrote:
> The 32bit selftest still doesn't work properly with sev-es, but that was
> a problem with the previous version too. I suspect there's some
> incompatibility between sev-es and the test, but I haven't been able to
> get a good answer on why that might be.

You are talking about test_32bit() in test_shadow_stack.c?

That test relies on a specific CET arch behavior. If you try to transition to a
32 bit compatibility mode segment with an SSP with high bits set (outside the 32
bit address space), a #GP will be triggered by the HW. The test verifies that
this happens and the kernel handles it appropriately. Could it be platform/mode
difference and not KVM issue?