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

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Message-Id: <BA71F1A6-1DF2-4683-9207-2305D1155239@gmail.com>
Date:	Mon, 18 Aug 2014 09:39:39 +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

This should have been a benign patch. I'll try to get windows 7 installation disk and check ASAP.

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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