linux-kernel - Re: [PATCH 1/10] KVM MMU: fix for calculating gpa in invlpg code

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Date:	Fri, 23 Apr 2010 20:05:17 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	KVM list <kvm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/10] KVM MMU: fix for calculating gpa in invlpg code



Avi Kivity wrote:
> On 04/22/2010 09:12 AM, Xiao Guangrong wrote:
>> If the guest is 32-bit, we should use 'quadrant' to adjust gpa
>> offset
>>
>>    
> 
> Good catch.  Only affects kvm_mmu_pte_write(), so I don't think this had
> ill effects other than not prefetching the correct address?
> 

Yes

>> @@ -478,9 +478,14 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu,
>> gva_t gva)
>>               ((level == PT_DIRECTORY_LEVEL&&  is_large_pte(*sptep))) ||
>>               ((level == PT_PDPE_LEVEL&&  is_large_pte(*sptep)))) {
>>               struct kvm_mmu_page *sp = page_header(__pa(sptep));
>> +            int offset = 0;
>> +
>> +            if (PTTYPE == 32)
>> +                offset = sp->role.quadrant<<  PT64_LEVEL_BITS;;
>>    
> 
> Wrong for PT_DIRECTORY_LEVEL (should be q << 8).  Also, too many
> semicolons.
> 

I guess you mean 'PT64_LEVEL_BITS' not 'PT_DIRECTORY_LEVEL' here :-)

It should be q << 8 here? it hardly understand, take leve = 1 for example,
32-bit guest PTE page table mapping range is 2^(10+12), PAE's PTE page table
mapping range is 2^(9+12), so, i think it's quadrant << 9 here, and other
function like FNAME(prefetch_page), FNAME(sync_page) also are q << 9

Sorry for the double semicolons here, will fix it

Thanks,
Xiao
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