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Date: Tue, 07 Jul 2009 18:32:59 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] qcow2: Fix L1 table memory allocation
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To: Avi Kivity <avi@redhat.com>
Cc: qemu-devel@nongnu.org

Avi Kivity schrieb:
> On 07/07/2009 07:09 PM, Kevin Wolf wrote:
>> Contrary to what one could expect, the size of L1 tables is not cluster
>> aligned. So as we're writing whole sectors now instead of single entries,
>> we need to ensure that the L1 table in memory is large enough; otherwise
>> write would access memory after the end of the L1 table.
>>
>>
>>       new_l1_size2 = sizeof(uint64_t) * new_l1_size;
>> -    new_l1_table = qemu_mallocz(new_l1_size2);
>> +    new_l1_table = qemu_mallocz(align_offset(new_l1_size2, 512));
>>       memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t));
>>    
> 
> Unrelated note: using qemu_memalign() here would reduce the copying for 
> cache=none.

Good point. I guess there are more places where we could use
qemu_memalign, so I would prefer to change them all in another patch.

Kevin