Re: [Xen-devel] [PATCH 02/12] early PV on HVM

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

> +static uint32_t xen_cpuid_base(void)
> +{
> +	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("XenVMMXenVMM", signature) && ((eax - base) >= 2))
> +			return base;
> +	}
> +
> +	return 0;
> +}

I forgot to mention this in the previous e-mail, but if you are rebasing
this against 2.6.34 it might be worth taking a look at the Microsoft HyperV code.
It also utilizes the cpuid code and this code could be made more generic.