linux-kernel - Re: [PATCH] x86: properly handle KVM emulation of hyperv

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Message-ID: <51E9A896.8070408@zytor.com>
Date:	Fri, 19 Jul 2013 13:59:02 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
CC:	Jason Wang <jasowang@...hat.com>, gleb@...hat.com,
	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Vadim Rozenfeld <vrozenfe@...hat.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>
Subject: Re: [PATCH] x86: properly handle KVM emulation of hyperv

On 07/19/2013 05:10 AM, Paolo Bonzini wrote:
>> +
>> +static inline bool kvm_para_available(void)
>> +{
>>  	if (boot_cpu_data.cpuid_level < 0)
>>  		return false;	/* So we don't blow up on old processors */
>>  
>>  	if (cpu_has_hypervisor) {
>> -		cpuid(KVM_CPUID_SIGNATURE, &eax, &ebx, &ecx, &edx);
>> -		memcpy(signature + 0, &ebx, 4);
>> -		memcpy(signature + 4, &ecx, 4);
>> -		memcpy(signature + 8, &edx, 4);
>> -		signature[12] = 0;
>> -
>> -		if (strcmp(signature, "KVMKVMKVM") == 0)
>> +		if (kvm_para_available_function(KVM_CPUID_SIGNATURE) ||
>> +		    kvm_para_available_function(KVM_CPUID_SIGNATURE_NEXT))
>>  			return true;
>>  	}
> 
> Nice catch.  Just one small thing, you should loop until 0x40010000, as
> done in arch/x86/include/asm/xen/hypervisor.h, in case one day a third
> hypervisor implements three extensions (Hyper-V, KVM and its own set).
> 

Any way we can centralize this stuff?

	-hpa


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