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Date: Wed, 17 Mar 2010 16:14:01 +0100
From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [Qemu-devel] [PATCH QEMU] Transparent Hugepage Support #3
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	<201003171505.57790.paul@codesourcery.com>
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To: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>

On Wed, Mar 17, 2010 at 03:05:57PM +0000, Paul Brook wrote:
> > +       if (size >= PREFERRED_RAM_ALIGN)
> > +               new_block->host = qemu_memalign(PREFERRED_RAM_ALIGN, size);
> > 
> 
> Is this deliberately bigger-than rather than multiple-of?
> Having the size not be a multiple of alignment seems somewhat strange, it's 
> always going to be wrong at one end...

Size not multiple I think is legitimate, the below-4G chunk isn't
required to end 2M aligned, all it matters is that the above-4G then
starts aligned. In short one thing to add in the future as parameter
to qemu_ram_alloc is the physical address that the host virtual
address corresponds to. The guest physical address that the host
retval corresponds to, has to be aligned with PREFERRED_RAM_ALIGN for
NPT/EPT to work. I don't think it's a big concern right now.