Re: [PATCH 3/4] KVM/X86: Enable Intel MPX for guest

[Paolo Bonzini <pbonzini@redhat.com>]

> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index a8ce117..e30d4ce 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -75,7 +75,7 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
>  			(best->eax | ((u64)best->edx << 32)) &
>  			host_xcr0 & KVM_SUPPORTED_XCR0;
>  		vcpu->arch.guest_xstate_size = best->ebx =
> -			xstate_required_size(vcpu->arch.guest_supported_xcr0);
> +			xstate_required_size(vcpu->arch.xcr0);
>  	}
>  
>  	kvm_pmu_cpuid_update(vcpu);
> ...
>  	kvm_put_guest_xcr0(vcpu);
>  	vcpu->arch.xcr0 = xcr0;
> +
> +	if ((xcr0 ^ old_xcr0) & XSTATE_EXTEND_MASK)
> +		kvm_update_cpuid(vcpu);
> +
>  	return 0;
>  }

These hunks should be part of the previous patch.

> @@ -5960,6 +5967,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  	preempt_disable();
>  
>  	kvm_x86_ops->prepare_guest_switch(vcpu);
> +	if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&

Shouldn't be necessary, setting xcr0 fails unless OSXSAVE=1.

> +		(vcpu->arch.xcr0 & (u64)(XSTATE_BNDREGS | XSTATE_BNDCSR)))
> +		kvm_x86_ops->fpu_activate(vcpu);

Can you explain this?

>  	if (vcpu->fpu_active)
>  		kvm_load_guest_fpu(vcpu);
>  	kvm_load_guest_xcr0(vcpu);
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 587fb9e..985e40e 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -122,7 +122,8 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,
>  	gva_t addr, void *val, unsigned int bytes,
>  	struct x86_exception *exception);
>  
> -#define KVM_SUPPORTED_XCR0	(XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
> +#define KVM_SUPPORTED_XCR0	(XSTATE_FP | XSTATE_SSE | XSTATE_YMM \
> +				| XSTATE_BNDREGS | XSTATE_BNDCSR)
>  extern u64 host_xcr0;
>  
>  extern struct static_key kvm_no_apic_vcpu;
> 

Otherwise looks straightforward.

Paolo