Re: [PATCH v5 17/19] KVM:x86: Enable guest CET supervisor xstate bit support

Paolo Bonzini
2023-08-04T22:03:27Z

On 8/3/23 06:27, Yang Weijiang wrote:
> if (boot_cpu_has(X86_FEATURE_XSAVES)) {
> + u32 eax, ebx, ecx, edx;
> +
> + cpuid_count(0xd, 1, &eax, &ebx, &ecx, &edx);
> rdmsrl(MSR_IA32_XSS, host_xss);
> kvm_caps.supported_xss = host_xss & KVM_SUPPORTED_XSS;
> + if (ecx & XFEATURE_MASK_CET_KERNEL)
> + kvm_caps.supported_xss |= XFEATURE_MASK_CET_KERNEL;
> }

This is a bit hackish and makes me lean more towards adding support for
XFEATURE_MASK_CET_KERNEL in host MSR_IA32_XSS (and then possibly hide it
in the actual calls to XSAVE/XRSTORS for non-guest FPU).

Paolo