linux-kernel - Re: [PATCH 33/61] KVM: x86: Handle PKU CPUID adjustment in VMX code

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Message-ID: <87v9nwnh3c.fsf@vitty.brq.redhat.com>
Date:   Mon, 24 Feb 2020 16:24:39 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 33/61] KVM: x86: Handle PKU CPUID adjustment in VMX code

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> Move the setting of the PKU CPUID bit into VMX to eliminate an instance
> of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in
> the common CPUID handling code.  Drop ->pku_supported(), CPUID
> adjustment was the only user.
>
> Note, some AMD CPUs now support PKU, but SVM doesn't yet support
> exposing it to a guest.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 1 -
>  arch/x86/kvm/cpuid.c            | 5 -----
>  arch/x86/kvm/svm.c              | 6 ------
>  arch/x86/kvm/vmx/capabilities.h | 5 -----
>  arch/x86/kvm/vmx/vmx.c          | 6 +++++-
>  5 files changed, 5 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 9baff70ad419..ba828569cda5 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1166,7 +1166,6 @@ struct kvm_x86_ops {
>  	bool (*xsaves_supported)(void);
>  	bool (*umip_emulated)(void);
>  	bool (*pt_supported)(void);
> -	bool (*pku_supported)(void);
>  
>  	int (*check_nested_events)(struct kvm_vcpu *vcpu, bool external_intr);
>  	void (*request_immediate_exit)(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 202a6c0f1db8..a1f46b3ca16e 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -341,7 +341,6 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry)
>  {
>  	unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0;
>  	unsigned f_la57;
> -	unsigned f_pku = kvm_x86_ops->pku_supported() ? F(PKU) : 0;
>  
>  	/* cpuid 7.0.ebx */
>  	const u32 kvm_cpuid_7_0_ebx_x86_features =
> @@ -381,10 +380,6 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry)
>  		cpuid_entry_mask(entry, CPUID_7_ECX);
>  		/* Set LA57 based on hardware capability. */
>  		entry->ecx |= f_la57;
> -		entry->ecx |= f_pku;
> -		/* PKU is not yet implemented for shadow paging. */
> -		if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
> -			cpuid_entry_clear(entry, X86_FEATURE_PKU);
>  
>  		entry->edx &= kvm_cpuid_7_0_edx_x86_features;
>  		cpuid_entry_mask(entry, CPUID_7_EDX);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index c0f8c09f3b04..630520f8adfa 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6094,11 +6094,6 @@ static bool svm_has_wbinvd_exit(void)
>  	return true;
>  }
>  
> -static bool svm_pku_supported(void)
> -{
> -	return false;
> -}
> -
>  #define PRE_EX(exit)  { .exit_code = (exit), \
>  			.stage = X86_ICPT_PRE_EXCEPT, }
>  #define POST_EX(exit) { .exit_code = (exit), \
> @@ -7457,7 +7452,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
>  	.xsaves_supported = svm_xsaves_supported,
>  	.umip_emulated = svm_umip_emulated,
>  	.pt_supported = svm_pt_supported,
> -	.pku_supported = svm_pku_supported,
>  
>  	.set_supported_cpuid = svm_set_supported_cpuid,
>  
> diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
> index 0a0b1494a934..7cae355e3490 100644
> --- a/arch/x86/kvm/vmx/capabilities.h
> +++ b/arch/x86/kvm/vmx/capabilities.h
> @@ -145,11 +145,6 @@ static inline bool vmx_umip_emulated(void)
>  		SECONDARY_EXEC_DESC;
>  }
>  
> -static inline bool vmx_pku_supported(void)
> -{
> -	return boot_cpu_has(X86_FEATURE_PKU);
> -}
> -
>  static inline bool cpu_has_vmx_rdtscp(void)
>  {
>  	return vmcs_config.cpu_based_2nd_exec_ctrl &
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 9d2e36a5ecb9..a9728cc0c343 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7113,6 +7113,11 @@ static void vmx_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
>  			cpuid_entry_set(entry, X86_FEATURE_INVPCID);
>  		if (vmx_umip_emulated())
>  			cpuid_entry_set(entry, X86_FEATURE_UMIP);
> +
> +		/* PKU is not yet implemented for shadow paging. */
> +		if (enable_ept && boot_cpu_has(X86_FEATURE_PKU) &&
> +		    boot_cpu_has(X86_FEATURE_OSPKE))
> +			cpuid_entry_set(entry, X86_FEATURE_PKU);
>  		break;
>  	default:
>  		break;
> @@ -7868,7 +7873,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
>  	.xsaves_supported = vmx_xsaves_supported,
>  	.umip_emulated = vmx_umip_emulated,
>  	.pt_supported = vmx_pt_supported,
> -	.pku_supported = vmx_pku_supported,
>  
>  	.request_immediate_exit = vmx_request_immediate_exit,

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly