Re: [PATCH v2 12/21] KVM:x86: Add fault checks for guest CR4.CET setting

[Yang, Weijiang]

On 5/5/2023 1:01 PM, Binbin Wu wrote:
> On 4/21/2023 9:46 PM, Yang Weijiang wrote: 
[...]
> > @@ -995,6 +995,9 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned 
> > long cr0)
> >           (is_64_bit_mode(vcpu) || kvm_is_cr4_bit_set(vcpu, 
> > X86_CR4_PCIDE)))
> >           return 1;
> >   +    if (!(cr0 & X86_CR0_WP) && kvm_read_cr4_bits(vcpu, X86_CR4_CET))
> You can use kvm_is_cr4_bit_set() instead of kvm_read_cr4_bits()

Good suggestion, thanks!

> > +        return 1;
> > +
> >       static_call(kvm_x86_set_cr0)(vcpu, cr0);
> >         kvm_post_set_cr0(vcpu, old_cr0, cr0);
> > @@ -1210,6 +1213,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned 
> > long cr4)
> >               return 1;
> >       }
> >   +    if ((cr4 & X86_CR4_CET) && !(kvm_read_cr0(vcpu) & X86_CR0_WP))
> You can use kvm_is_cr0_bit_set() to check X86_CR0_WP

OK.

> > +        return 1;
> > +
[...]
> > @@ -536,6 +536,9 @@ bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 
> > index, u32 type);
> >           __reserved_bits |= X86_CR4_VMXE;        \
> >       if (!__cpu_has(__c, X86_FEATURE_PCID))          \
> >           __reserved_bits |= X86_CR4_PCIDE;       \
> > +    if (!__cpu_has(__c, X86_FEATURE_SHSTK) &&    \
> > +        !__cpu_has(__c, X86_FEATURE_IBT))        \
> > +        __reserved_bits |= X86_CR4_CET;        \
> IMO, it is a bit wired to split this part from the change of 
> CR4_RESERVED_BITS.

Make sense, will move these lines to other patch.

> > __reserved_bits;                                \
> >   })