linux-kernel - Re: [PATCH 11/15] KVM: x86/MMU: Refactor vmx_get_mt

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Date:   Thu, 18 Nov 2021 09:30:14 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Ben Gardon <bgardon@...gle.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>,
        Yulei Zhang <yulei.kernel@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        Kai Huang <kai.huang@...el.com>,
        Keqian Zhu <zhukeqian1@...wei.com>,
        David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH 11/15] KVM: x86/MMU: Refactor vmx_get_mt_mask

On 11/16/21 00:45, Ben Gardon wrote:
> Remove the gotos from vmx_get_mt_mask to make it easier to separate out
> the parts which do not depend on vcpu state.
> 
> No functional change intended.
> 
> 
> Signed-off-by: Ben Gardon <bgardon@...gle.com>

Queued, thanks (with a slightly edited commit message; the patch is a 
simplification anyway).

Paolo

> ---
>   arch/x86/kvm/vmx/vmx.c | 23 +++++++----------------
>   1 file changed, 7 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 71f54d85f104..77f45c005f28 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6987,7 +6987,6 @@ static int __init vmx_check_processor_compat(void)
>   static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
>   {
>   	u8 cache;
> -	u64 ipat = 0;
>   
>   	/* We wanted to honor guest CD/MTRR/PAT, but doing so could result in
>   	 * memory aliases with conflicting memory types and sometimes MCEs.
> @@ -7007,30 +7006,22 @@ static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
>   	 * EPT memory type is used to emulate guest CD/MTRR.
>   	 */
>   
> -	if (is_mmio) {
> -		cache = MTRR_TYPE_UNCACHABLE;
> -		goto exit;
> -	}
> +	if (is_mmio)
> +		return MTRR_TYPE_UNCACHABLE << VMX_EPT_MT_EPTE_SHIFT;
>   
> -	if (!kvm_arch_has_noncoherent_dma(vcpu->kvm)) {
> -		ipat = VMX_EPT_IPAT_BIT;
> -		cache = MTRR_TYPE_WRBACK;
> -		goto exit;
> -	}
> +	if (!kvm_arch_has_noncoherent_dma(vcpu->kvm))
> +		return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT) | VMX_EPT_IPAT_BIT;
>   
>   	if (kvm_read_cr0(vcpu) & X86_CR0_CD) {
> -		ipat = VMX_EPT_IPAT_BIT;
>   		if (kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED))
>   			cache = MTRR_TYPE_WRBACK;
>   		else
>   			cache = MTRR_TYPE_UNCACHABLE;
> -		goto exit;
> -	}
>   
> -	cache = kvm_mtrr_get_guest_memory_type(vcpu, gfn);
> +		return (cache << VMX_EPT_MT_EPTE_SHIFT) | VMX_EPT_IPAT_BIT;
> +	}
>   
> -exit:
> -	return (cache << VMX_EPT_MT_EPTE_SHIFT) | ipat;
> +	return kvm_mtrr_get_guest_memory_type(vcpu, gfn) << VMX_EPT_MT_EPTE_SHIFT;
>   }
>   
>   static void vmcs_set_secondary_exec_control(struct vcpu_vmx *vmx, u32 new_ctl)
>