linux-kernel - Re: [PATCH] KVM MMU: check reserved bits only if CR4.PSE=1 or CR4.PAE=1

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Message-ID: <4B9F1F47.2040700@cn.fujitsu.com>
Date:	Tue, 16 Mar 2010 14:03:51 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Sheng Yang <sheng@...ux.intel.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM MMU: check reserved bits only if CR4.PSE=1 or CR4.PAE=1



Avi Kivity wrote:
> On 03/16/2010 08:21 PM, Xiao Guangrong wrote:
>> The RSV bit is possibility set in error code when #PF occurred
>> only if CR4.PSE=1 or CR4.PAE=1
>>
>> Signed-off-by: Xiao Guangrong<xiaoguangrong@...fujitsu.com>
>> ---
>>   arch/x86/kvm/mmu.c |    3 +++
>>   1 files changed, 3 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index 741373e..36e50ab 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -2270,6 +2270,9 @@ static bool is_rsvd_bits_set(struct kvm_vcpu
>> *vcpu, u64 gpte, int level)
>>   {
>>       int bit7;
>>
>> +    if (!is_pae(vcpu)&&  !is_pse(vcpu))
>> +        return 0;
>> +
>>       bit7 = (gpte>>  7)&  1;
>>       return (gpte&  vcpu->arch.mmu.rsvd_bits_mask[bit7][level-1]) != 0;
>>   }
>>    
> 
> Should be handled by reset_rsvd_bits_mask(), so that all reserved bit
> handling happens in one place.
> 

OK, will fix it.

> I think the only change is that is !is_pse(vcpu) we ignore bit 7?

If the vcpu is in PT32E_ROOT_LEVEL/PT64_ROOT_LEVEL mode, CR4.PAE
is aways enabled, so what we need do is ignore bit7 if !is_pse(vcpu)
under PT32_ROOT_LEVEL mode, right?

Thanks,
Xiao
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