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

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Message-ID: <20140818081115.GA26307@kernel>
Date:	Mon, 18 Aug 2014 16:11:15 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Nadav Amit <nadav.amit@...il.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

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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