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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <1443515898-3594-48-git-send-email-dgilbert@redhat.com> (David
	Alan Gilbert's message of "Tue, 29 Sep 2015 09:38:11 +0100")
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	<1443515898-3594-48-git-send-email-dgilbert@redhat.com>
Date: Wed, 28 Oct 2015 12:28:34 +0100
Message-ID: <87oafj8c65.fsf@neno.neno>
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Subject: Re: [Qemu-devel] [PATCH v8 47/54] Round up RAMBlock sizes to host
	page sizes
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To: "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>
Cc: aarcange@redhat.com, liang.z.li@intel.com, qemu-devel@nongnu.org, luis@cs.umu.se, bharata@linux.vnet.ibm.com, amit.shah@redhat.com, pbonzini@redhat.com

"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> RAMBlocks that are not a multiple of host pages in length
> cause problems for postcopy (I've seen an ACPI table on aarch64
> be 5k in length - i.e. 5x target-page), so round RAMBlock sizes
> up to a host-page.
>
> This potentially breaks migration compatibility due to changes
> in RAMBlock sizes; however:
>    1) x86 and s390 I think always have host=target page size
>    2) When I've tried on Power the block sizes already seem aligned.
>    3) I don't think there's anything else that maintains per-version
>       machine-types for compatibility.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

We had this problem on the past when we moved the machines to be
Megabyte rounded size, some machines where not.  But in this particular
case, I will clame that having a size that is _not_ of the size of the
host pages is just asking for trouble.