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

From: Paolo Bonzini
Date: Fri Aug 04 2023 - 18:03:27 EST

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;
+ 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).