On Mon, 2019-03-04 at 12:14 +0100, Paolo Bonzini wrote: > On 04/03/19 12:10, Xiaoyao Li wrote: > > Like you said before, I think we don't need the condition judgment > > "if(boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))", but to set > > F(CORE_CAPABILITY) > > always for guest since MSR_IA32_CORE_CAPABILITY is emulated. > > > > And we should set the right emulated value of MSR_IA32_CORE_CAPABILITY for > > guest > > in function kvm_get_core_capability() based on whether > > boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT) just as you commented in the > > next > > patch. > > Yes, that would certainly be better. However, you'd also have to move > MSR_IA32_CORE_CAPABILITY handling to x86.c, because you'd have to enable > X86_FEATURE_CORE_CAPABILITY for AMD. > > Paolo Hi, Paolo I just notice that F(ARCH_CAPABILITIES) is set unconditionally. However the handling of MSR_IA32_ARCH_CAPABILITIES only exists with vmx, and the emulation of this MSR is in vmx->arch_capabilities. These will cause #GP when guest kernel rdmsr(MSR_IA32_ARCH_CAPABILITES) with AMD CPU since there is handling for svm. Maybe what I think is not correct due to my limit knowledge of MSR_IA32_ARCH_CAPABILITIES and how kernel handles its related features. If what I said above is true and it's indeed an issue. So based on the fact that both MSR_IA32_ARCH_CAPABILITIES and MSR_IA32_CORE_CAPABILITY are feature- enumerating MSR and we emulate them in KVM, there are 2 choices for us to handle it: 1. we unconditionally set F(ARCH_CAPABILITIES) and F(CORE_CAPABILITY) for guest, move the emulation of these 2 MSRs to vcpu->arch.***, and move all the handling of these 2 MSRs to x86.c. 2. we conditionally set F(ARCH_CAPABILITIES) and F(CORE_CAPABILITY) only if it is intel CPU. So we just need to emulate these 2 MSRs in vmx->*** for intel CPU. I prefer option 2 personally for CORE_CAPABILITY since it makes no sense to expose MSR_IA32_CORE_CAPABILITY to other x86 vendors. About ARCH_CAPABILITIES, it seems that we emulate it for generic x86 cpus that !x86_match_cpu(cpu_no_speculation). So we should choose option 1, to move the emulation and handling to x86.c? Xiaoyao
