linux-kernel - Re: [PATCH 1/4] x86: introduce hypervisor_cpuid

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Message-ID: <51EE553C.40305@zytor.com>
Date:	Tue, 23 Jul 2013 03:04:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jason Wang <jasowang@...hat.com>
CC:	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	gleb@...hat.com, pbonzini@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] x86: introduce hypervisor_cpuid_base()

On 07/23/2013 02:41 AM, Jason Wang wrote:
>  
> +static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
> +{
> +	uint32_t base, eax, ebx, ecx, edx;
> +	char signature[13];
> +
> +	for (base = 0x40000000; base < 0x40010000; base += 0x100) {
> +		cpuid(base, &eax, &ebx, &ecx, &edx);
> +		*(uint32_t *)(signature + 0) = ebx;
> +		*(uint32_t *)(signature + 4) = ecx;
> +		*(uint32_t *)(signature + 8) = edx;
> +		signature[12] = 0;
> +
> +		if (!strcmp(sig, signature) &&
> +		    (leaves == 0 || ((eax - base) >= leaves)))
> +			return base;
> +	}
> +
> +	return 0;
> +}
> +

Hmm... how about:

uint32_t sign[3];

	cpuid(base, &eax, &sign[0], &sign[1], &sign[2]);

	if (!memcmp(sig, sign, 12) && ...);

	-hpa

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