linux-kernel - Re: [PATCH] KVM: x86: Increase the number of fixed MTRR regs to 10

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Message-Id: <A04378F6-A6B1-46B8-B306-A9A2115F54C7@gmail.com>
Date:	Mon, 18 Aug 2014 12:39:36 +0300
From:	Nadav Amit <nadav.amit@...il.com>
To:	Wanpeng Li <wanpeng.li@...ux.intel.com>
Cc:	Nadav Amit <namit@...technion.ac.il>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"gleb@...nel.org" <gleb@...nel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: Increase the number of fixed MTRR regs to 10

I reproduced the blue-screen. Let me to to figure it out.

Nadav

On Aug 18, 2014, at 11:11 AM, Wanpeng Li <wanpeng.li@...ux.intel.com> wrote:

> On Mon, Aug 18, 2014 at 09:39:39AM +0300, Nadav Amit wrote:
>> This should have been a benign patch. I'll try to get windows 7 installation disk and check ASAP.
>> 
> 
> In addition, it just can be reproduced on 32bit win7 w/ MP enabled, in
> case UP can't be reproduced.
> 
> Regards,
> Wanpeng Li 
> 
>> Nadav
>> 
>>> On 18 Aug 2014, at 05:17, Wanpeng Li <wanpeng.li@...ux.intel.com> wrote:
>>> 
>>> Hi Nadav,
>>>> On Wed, Jun 18, 2014 at 05:21:19PM +0300, Nadav Amit wrote:
>>>> Recent Intel CPUs have 10 variable range MTRRs. Since operating systems
>>>> sometime make assumptions on CPUs while they ignore capability MSRs, it is
>>>> better for KVM to be consistent with recent CPUs. Reporting more MTRRs than
>>>> actually supported has no functional implications.
>>>> 
>>>> Signed-off-by: Nadav Amit <namit@...technion.ac.il>
>>>> ---
>>>> arch/x86/include/asm/kvm_host.h | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>> 
>>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>>>> index 4931415..0bab29d 100644
>>>> --- a/arch/x86/include/asm/kvm_host.h
>>>> +++ b/arch/x86/include/asm/kvm_host.h
>>>> @@ -95,7 +95,7 @@ static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
>>>> #define KVM_REFILL_PAGES 25
>>>> #define KVM_MAX_CPUID_ENTRIES 80
>>>> #define KVM_NR_FIXED_MTRR_REGION 88
>>>> -#define KVM_NR_VAR_MTRR 8
>>>> +#define KVM_NR_VAR_MTRR 10
>>> 
>>> We observed that there is obvious regression caused by this commit, 32bit 
>>> win7 guest show blue screen during boot.
>>> 
>>> Regards,
>>> Wanpeng Li 
>>> 
>>>> #define ASYNC_PF_PER_VCPU 64
>>>> 
>>>> -- 
>>>> 1.9.1
>>>> 
>>>> --
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