Re: [Qemu-devel] [PATCH] qcow2: Fix L1 table memory allocation

[malc]

On Tue, 7 Jul 2009, Avi Kivity wrote:

> 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.
> 

Another unrelated note, qemu_memalign(and by extension qemu_vmalloc)
is NULL happy. And FWIW 487414f1cbd638beb0227c7da71fe7b8a821e155
removed NULL checks for qemu_memalgn and after that new code was added
that doesn't check for NULLs either (for instance e3f4e2a4 which has
bitten me).
   
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