linux-kernel - Re: [PATCH] KVM: x86: fix bogus warning about reserved bits

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Date:	Mon, 28 Sep 2015 11:16:43 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: fix bogus warning about reserved bits



On 09/25/2015 03:49 PM, Paolo Bonzini wrote:
>
>
> On 24/09/2015 12:12, Borislav Petkov wrote:
>> On Thu, Sep 24, 2015 at 11:23:08AM +0800, Xiao Guangrong wrote:
>>>> +static inline bool
>>>> +boot_cpu_is_amd(void)
>>>> +{
>>>> +	WARN_ON_ONCE(!tdp_enabled);
>>>> +	return shadow_x_mask != 0;
>>>
>>> shadow_x_mask != 0 is Intel's CPU.
>>>
>>> Borislav, could you please check shadow_x_mask == 0 instead and test it again?
>>
>> That did the trick:
>>
>> [   62.640392] kvm: zapping shadow pages for mmio generation wraparound
>> [   63.100301] cpuid(0).ebx = 68747541
>> [   63.193426] kvm [3748]: vcpu0 unhandled rdmsr: 0xc0010112
>> [   64.538294] kvm [3748]: vcpu0 unhandled rdmsr: 0xc0011021
>> [   64.866263] kvm [3748]: vcpu1 unhandled rdmsr: 0xc0011021
>> [   64.971972] kvm [3748]: vcpu2 unhandled rdmsr: 0xc0011021
>> [   65.070376] kvm [3748]: vcpu3 unhandled rdmsr: 0xc0011021
>> [   65.170625] kvm [3748]: vcpu4 unhandled rdmsr: 0xc0011021
>> [   65.272838] kvm [3748]: vcpu5 unhandled rdmsr: 0xc0011021
>> [   65.374288] kvm [3748]: vcpu6 unhandled rdmsr: 0xc0011021
>> [   65.474825] kvm [3748]: vcpu7 unhandled rdmsr: 0xc0011021
>>
>> That's all I got in dmesg from booting the guest - no more mmio PF
>> warnings.
>
> Great, though this doesn't yet explain why guest_cpuid_is_amd failed.
> I'll look into it next week when Amazon delivers my shiny new AMD
> mini-PC :) and send the patch to Linus meanwhile.

I guess QEMU passed AMD cpu mode to KVM... but not sure. :(
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