linux-kernel - Re: [PATCH 41/61] KVM: x86: Move XSAVES CPUID adjust to VMX's KVM cpu cap update

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Date:   Mon, 24 Feb 2020 22:43:20 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.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 41/61] KVM: x86: Move XSAVES CPUID adjust to VMX's KVM cpu cap update

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

> Move the clearing of the XSAVES CPUID bit into VMX, which has a separate
> VMCS control to enable XSAVES in non-root, to eliminate the last ugly
> renmant of the undesirable "unsigned f_* = *_supported ? F(*) : 0"
> pattern in the common CPUID handling code.
>
> Drop ->xsaves_supported(), CPUID adjustment was the only user.
>
> 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            | 4 ----
>  arch/x86/kvm/svm.c              | 6 ------
>  arch/x86/kvm/vmx/vmx.c          | 5 ++++-
>  4 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 ba828569cda5..dd690fb5ceca 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1163,7 +1163,6 @@ struct kvm_x86_ops {
>  	void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu,
>  		enum exit_fastpath_completion *exit_fastpath);
>  
> -	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 c2a4c9df49a9..77a6c1db138d 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -626,10 +626,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>  			goto out;
>  
>  		cpuid_entry_mask(entry, CPUID_D_1_EAX);
> -
> -		if (!kvm_x86_ops->xsaves_supported())
> -			cpuid_entry_clear(entry, X86_FEATURE_XSAVES);
> -
>  		if (entry->eax & (F(XSAVES)|F(XSAVEC)))
>  			entry->ebx = xstate_required_size(supported_xcr0, true);
>  		else
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index f98a192459f7..7cb05945162e 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6080,11 +6080,6 @@ static bool svm_rdtscp_supported(void)
>  	return boot_cpu_has(X86_FEATURE_RDTSCP);
>  }
>  
> -static bool svm_xsaves_supported(void)
> -{
> -	return boot_cpu_has(X86_FEATURE_XSAVES);
> -}
> -
>  static bool svm_umip_emulated(void)
>  {
>  	return false;
> @@ -7455,7 +7450,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
>  	.cpuid_update = svm_cpuid_update,
>  
>  	.rdtscp_supported = svm_rdtscp_supported,
> -	.xsaves_supported = svm_xsaves_supported,
>  	.umip_emulated = svm_umip_emulated,
>  	.pt_supported = svm_pt_supported,
>  
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index bae915431c72..cfd0ef314176 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7131,6 +7131,10 @@ static __init void vmx_set_cpu_caps(void)
>  	    boot_cpu_has(X86_FEATURE_OSPKE))
>  		kvm_cpu_cap_set(X86_FEATURE_PKU);
>  
> +	/* CPUID 0xD.1 */
> +	if (!vmx_xsaves_supported())
> +		kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
> +
>  	/* CPUID 0x80000001 */
>  	if (!cpu_has_vmx_rdtscp())
>  		kvm_cpu_cap_clear(X86_FEATURE_RDTSCP);
> @@ -7886,7 +7890,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
>  
>  	.check_intercept = vmx_check_intercept,
>  	.handle_exit_irqoff = vmx_handle_exit_irqoff,
> -	.xsaves_supported = vmx_xsaves_supported,
>  	.umip_emulated = vmx_umip_emulated,
>  	.pt_supported = vmx_pt_supported,

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

-- 
Vitaly