linux-kernel - Re: [PATCH 15/61] KVM: x86: Refactor CPUID 0x4 and 0x8000001d handling

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Message-ID: <871rqorol3.fsf@vitty.brq.redhat.com>
Date:   Fri, 21 Feb 2020 15:40:08 +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 15/61] KVM: x86: Refactor CPUID 0x4 and 0x8000001d handling

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

> Refactoring the sub-leaf handling for CPUID 0x4/0x8000001d to eliminate
> a one-off variable and its associated brackets.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/cpuid.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 5044a595799f..d75d539da759 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -545,20 +545,16 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
>  		break;
>  	/* functions 4 and 0x8000001d have additional index. */
>  	case 4:
> -	case 0x8000001d: {
> -		int cache_type;
> -
> -		/* read more entries until cache_type is zero */
> -		for (i = 1; ; ++i) {
> -			cache_type = entry[i - 1].eax & 0x1f;
> -			if (!cache_type)
> -				break;
> -
> +	case 0x8000001d:
> +		/*
> +		 * Read entries until the cache type in the previous entry is
> +		 * zero, i.e. indicates an invalid entry.
> +		 */
> +		for (i = 1; entry[i - 1].eax & 0x1f; ++i) {
>  			if (!do_host_cpuid(&entry[i], nent, maxnent, function, i))
>  				goto out;
>  		}
>  		break;
> -	}
>  	case 6: /* Thermal management */
>  		entry->eax = 0x4; /* allow ARAT */
>  		entry->ebx = 0;

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

-- 
Vitaly