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Re: [Qemu-ppc] [Qemu-devel] [PATCH 11/17] pseries: savevm support for ps

From: Anthony Liguori
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH 11/17] pseries: savevm support for pseries machine
Date: Mon, 08 Jul 2013 14:01:28 -0500
User-agent: Notmuch/0.15.2+202~g0c4b8aa (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu)

Alexander Graf <address@hidden> writes:

> On 08.07.2013, at 20:45, Anthony Liguori wrote:
>> Alexey Kardashevskiy <address@hidden> writes:
>>> From: David Gibson <address@hidden>
>>> This adds the necessary pieces to implement savevm / migration for the
>>> pseries machine.  The most complex part here is migrating the hash
>>> table - for the paravirtualized pseries machine the guest's hash page
>>> table is not stored within guest memory, but externally and the guest
>>> accesses it via hypercalls.
>>> This patch uses a hypervisor reserved bit of the HPTE as a dirty bit
>>> (tracking changes to the HPTE itself, not the page it references).
>>> This is used to implement a live migration style incremental save and
>>> restore of the hash table contents.
>>> In addition it adds VMStateDescription information to save and restore
>>> the (few) remaining pieces of state information needed by the pseries
>>> machine.
>>> Signed-off-by: David Gibson <address@hidden>
>>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>> I vaguely recall making the suggestion to use a live section like this.
>> How large is the HTAB typically?
> The default for HV KVM is at 16MB IIRC.

And if I recall since it's a hash table, updates are random access and
not at all page aligned making using qemu ram quite unusable for this

I guess:

Reviewed-by: Anthony Liguori <address@hidden>


Anthony Liguori

> Alex

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