On Thu, Apr 23, 2020 at 10:34:50AM -0700, Sean Christopherson wrote:
> On Thu, Mar 26, 2020 at 04:18:42PM +0800, Yang Weijiang wrote:
> > CPUID(0xd, 1) reports the current required storage size of
> > struct kvm_pio_request pio;
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index 78d461be2102..25e9a11291b3 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -95,9 +95,24 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
> > }
> >
> > best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
> > - if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
> > - cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
> > - best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
> > + if (best) {
> > + if (best->eax & (F(XSAVES) | F(XSAVEC))) {
>
> Please use cpuid_entry_has() to preserve the automagic register lookup and
> compile-time assertions that are provided. E.g. I don't know off the top
> of my whether %eax is the correct register, and I don't want to know :-).
>
Got it, will fix it.
> > + u64 xstate = vcpu->arch.xcr0 | vcpu->arch.ia32_xss;
> > +
> > + best->ebx = xstate_required_size(xstate, true);
> > + }
> > +
> > + if (best->eax & F(XSAVES)) {
>
> Same thing here.
>
> > + vcpu->arch.guest_supported_xss =
> > + (best->ecx | ((u64)best->edx << 32)) & supported_xss;
>
> The indentation is funky, I'm guessing you're trying to squeak in less than
> 80 chars. Maybe this?
>
> if (!cpuid_entry_has(best, X86_FEATURE_XSAVES)) {
> best->ecx = 0;
> best->edx = 0;
> }
>
> vcpu->arch.guest_supported_xss =
> (((u64)best->edx << 32) | best->ecx) & supported_xss;
>
> Nit: my preference is to have the high half first, x86 is little endian
> (the xcr0 code is "wrong" :-D). For me, this also makes it more obvious
> that the effective size is a u64.
>
Good suggestion, will fixed it together the xcr0 part!
> > + } else {
> > + best->ecx = 0;
> > + best->edx = 0;
> > + vcpu->arch.guest_supported_xss = 0;
> > + }
> > + } else {
> > + vcpu->arch.guest_supported_xss = 0;
> > + }
> >
> > /*
> > * The existing code assumes virtual address is 48-bit or 57-bit in the
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 90acdbbb8a5a..51ecb496d47d 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -2836,9 +2836,12 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > * IA32_XSS[bit 8]. Guests have to use RDMSR/WRMSR rather than
> > * XSAVES/XRSTORS to save/restore PT MSRs.
> > */
> > - if (data & ~supported_xss)
> > + if (data & ~vcpu->arch.guest_supported_xss)
> > return 1;
> > - vcpu->arch.ia32_xss = data;
> > + if (vcpu->arch.ia32_xss != data) {
> > + vcpu->arch.ia32_xss = data;
> > + kvm_update_cpuid(vcpu);
> > + }
> > break;
> > case MSR_SMI_COUNT:
> > if (!msr_info->host_initiated)
> > @@ -9635,6 +9638,8 @@ int kvm_arch_hardware_setup(void)
> >
> > if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
> > supported_xss = 0;
> > + else
> > + supported_xss = host_xss & KVM_SUPPORTED_XSS;
>
> Silly nit: I'd prefer to invert the check, e.g.
>
> if (kvm_cpu_cap_has(X86_FEATURE_XSAVES))
> supported_xss = host_xss & KVM_SUPPORTED_XSS;
> else
> supported_xss = 0;
Fair enough!
>
> >
> > cr4_reserved_bits = kvm_host_cr4_reserved_bits(&boot_cpu_data);
> >
> > --
> > 2.17.2
> >
