On Tue, Dec 27, 2022 at 10:38 AM Aaron Lewis <aaronlewis@xxxxxxxxxx> wrote: > > Be good citizens by clearing both > CPUID.(EAX=0DH,ECX=0):EAX.XTILECFG[bit-17] and > CPUID.(EAX=0DH,ECX=0):EAX.XTILEDATA[bit-18] if they are both not set. > That way userspace or a guest doesn't fail if it attempts to set XCR0 > with the user xfeature bits, i.e. EDX:EAX of CPUID.(EAX=0DH,ECX=0). > > Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> > Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx> > --- > arch/x86/kvm/cpuid.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 0b5bf013fcb8e..2d9910847786a 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -977,6 +977,10 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > u64 permitted_xcr0 = kvm_caps.supported_xcr0 & xstate_get_guest_group_perm(); > u64 permitted_xss = kvm_caps.supported_xss; > > + if (!(permitted_xcr0 & XFEATURE_MASK_XTILE_CFG) || > + !(permitted_xcr0 & XFEATURE_MASK_XTILE_DATA)) > + permitted_xcr0 &= ~XFEATURE_MASK_XTILE; > + > entry->eax &= permitted_xcr0; > entry->ebx = xstate_required_size(permitted_xcr0, false); > entry->ecx = entry->ebx; > -- > 2.39.0.314.g84b9a713c41-goog > Two questions: 1) Under what circumstances would this happen? 2) Shouldn't we also clear XFEATURE_MASK_CFG if both bits are not set?
