Re: [PATCH 21/61] KVM: x86: Use supported_xcr0 to detect MPX support

[Vitaly Kuznetsov]

Sean Christopherson <sean.j.christopherson@xxxxxxxxx> writes:

> Query supported_xcr0 when checking for MPX support instead of invoking
> ->mpx_supported() and drop ->mpx_supported() as kvm_mpx_supported() was
> its last user.  Rename vmx_mpx_supported() to cpu_has_vmx_mpx() to
> better align with VMX/VMCS nomenclature.
>
> Modify VMX's adjustment of xcr0 to call cpus_has_vmx_mpx() (renamed from
> vmx_mpx_supported()) directly to avoid reading supported_xcr0 before
> it's fully configured.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm_host.h | 2 +-
>  arch/x86/kvm/cpuid.c            | 3 +--
>  arch/x86/kvm/svm.c              | 6 ------
>  arch/x86/kvm/vmx/capabilities.h | 2 +-
>  arch/x86/kvm/vmx/vmx.c          | 3 +--
>  5 files changed, 4 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 77d206a93658..85f0d96cfeb2 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1163,7 +1163,7 @@ struct kvm_x86_ops {
>  			       enum x86_intercept_stage stage);
>  	void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu,
>  		enum exit_fastpath_completion *exit_fastpath);
> -	bool (*mpx_supported)(void);
> +
>  	bool (*xsaves_supported)(void);
>  	bool (*umip_emulated)(void);
>  	bool (*pt_supported)(void);
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index b9763eb711cb..84006cc4007c 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -47,8 +47,7 @@ static u32 xstate_required_size(u64 xstate_bv, bool compacted)
>  
>  bool kvm_mpx_supported(void)
>  {
> -	return ((host_xcr0 & (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR))
> -		 && kvm_x86_ops->mpx_supported());
> +	return supported_xcr0 & (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR);
>  }
>  EXPORT_SYMBOL_GPL(kvm_mpx_supported);
>  
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index af096c4f9c5f..3c7ddaff405d 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6082,11 +6082,6 @@ static bool svm_invpcid_supported(void)
>  	return false;
>  }
>  
> -static bool svm_mpx_supported(void)
> -{
> -	return false;
> -}
> -
>  static bool svm_xsaves_supported(void)
>  {
>  	return boot_cpu_has(X86_FEATURE_XSAVES);
> @@ -7468,7 +7463,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
>  
>  	.rdtscp_supported = svm_rdtscp_supported,
>  	.invpcid_supported = svm_invpcid_supported,
> -	.mpx_supported = svm_mpx_supported,
>  	.xsaves_supported = svm_xsaves_supported,
>  	.umip_emulated = svm_umip_emulated,
>  	.pt_supported = svm_pt_supported,
> diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
> index 1a6a99382e94..0a0b1494a934 100644
> --- a/arch/x86/kvm/vmx/capabilities.h
> +++ b/arch/x86/kvm/vmx/capabilities.h
> @@ -100,7 +100,7 @@ static inline bool cpu_has_load_perf_global_ctrl(void)
>  	       (vmcs_config.vmexit_ctrl & VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL);
>  }
>  
> -static inline bool vmx_mpx_supported(void)
> +static inline bool cpu_has_vmx_mpx(void)
>  {
>  	return (vmcs_config.vmexit_ctrl & VM_EXIT_CLEAR_BNDCFGS) &&
>  		(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_BNDCFGS);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 32a84ec15064..98fd651f7f7e 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7590,7 +7590,7 @@ static __init int hardware_setup(void)
>  		WARN_ONCE(host_bndcfgs, "KVM: BNDCFGS in host will be lost");
>  	}
>  
> -	if (!kvm_mpx_supported())
> +	if (!cpu_has_vmx_mpx())
>  		supported_xcr0 &= ~(XFEATURE_MASK_BNDREGS |
>  				    XFEATURE_MASK_BNDCSR);
>  
> @@ -7857,7 +7857,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
>  
>  	.check_intercept = vmx_check_intercept,
>  	.handle_exit_irqoff = vmx_handle_exit_irqoff,
> -	.mpx_supported = vmx_mpx_supported,
>  	.xsaves_supported = vmx_xsaves_supported,
>  	.umip_emulated = vmx_umip_emulated,
>  	.pt_supported = vmx_pt_supported,

Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

-- 
Vitaly