linux-kernel - Re: [PATCH 3/3] kvm mmu: alloc shadow pages with __GFP

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Date:	Wed, 18 Feb 2009 14:14:16 +0000
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] kvm mmu: alloc shadow pages with __GFP_ZERO

Joerg Roedel wrote:
>> sp->spt is allocated using mmu_memory_cache_alloc(), which zeros the page.  How can the assertion fail?
>>     
>
> In the code I see (current kvm-git) mmu_memory_cache_alloc() does zero
> nothing. It takes the page from the preallocated pool and returns it.
> The pool itself is filled with mmu_topup_memory_caches() which calls
> mmu_topup_memory_cache_page() to fill the mmu_page_cache (from which the
> sp->spt page is allocated later). And the mmu_topup_memory_cache_page()
> function calls alloc_page() and does not zero the result. This let the
> assertion trigger.
>   

Right, I was looking at the 2.6.29 tree.  The patch is correct (and the 
others look good as well).  As usual, I'd like Marcelo to take a look as 
well.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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