linux-kernel - Re: [PATCH 36/61] KVM: x86: Handle GBPAGE CPUID adjustment for EPT in VMX code

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Date:   Mon, 24 Feb 2020 16:34:52 +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 36/61] KVM: x86: Handle GBPAGE CPUID adjustment for EPT in VMX code

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

> Move the clearing of the GBPAGE CPUID bit into VMX to eliminate an
> instance of the undesirable "unsigned f_* = *_supported ? F(*) : 0"
> pattern in the common CPUID handling code, and to pave the way toward
> eliminating ->get_lpage_level().
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/cpuid.c   | 3 +--
>  arch/x86/kvm/vmx/vmx.c | 2 ++
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index f4a3655451dd..c74253202af8 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -416,8 +416,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>  	int r, i, max_idx;
>  	unsigned f_nx = is_efer_nx() ? F(NX) : 0;
>  #ifdef CONFIG_X86_64
> -	unsigned f_gbpages = (kvm_x86_ops->get_lpage_level() == PT_PDPE_LEVEL)
> -				? F(GBPAGES) : 0;
> +	unsigned f_gbpages = F(GBPAGES);
>  	unsigned f_lm = F(LM);
>  #else
>  	unsigned f_gbpages = 0;
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index fcec3d8a0176..11b9c1e7e520 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7125,6 +7125,8 @@ static void vmx_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
>  	case 0x80000001:
>  		if (!cpu_has_vmx_rdtscp())
>  			cpuid_entry_clear(entry, X86_FEATURE_RDTSCP);
> +		if (enable_ept && !cpu_has_vmx_ept_1g_page())
> +			cpuid_entry_clear(entry, X86_FEATURE_GBPAGES);
>  		break;
>  	default:
>  		break;

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

-- 
Vitaly