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Re: [Qemu-devel] vm state save/restore question
From: |
Alexander Graf |
Subject: |
Re: [Qemu-devel] vm state save/restore question |
Date: |
Wed, 20 Jun 2012 01:30:26 +0200 |
On 20.06.2012, at 01:28, Benjamin Herrenschmidt wrote:
> On Wed, 2012-06-20 at 01:11 +0200, Juan Quintela wrote:
>>
>>> I am confident I can come up with something as far as the kernel and
>>> qemu <-> kernel interface goes. I need to get my head around the details
>>> on how to implement that two stage save process in qemu though and the
>>> corresponding restore which will need to read both snapshots and apply
>>> the diff before shooting it back to the kernel.
>>>
>>> BTW. Does migration in pure qemu (full system emu) works similarily, ie,
>>> two stage ? If it does I can easily prototype everything there.
>>
>> It does, but I have no clue how the hashed page tables are implemented
>> on ppc, i.e. if there is anything specific for bare metal. Alex?
>
> We support the paravirtualized -M pseries in full emu as well, in which
> case the hashed page table is handled by qemu itself who implements the
> H_ENTER & co hypercalls. So it's very similar, except that qemu doesn't
> have to ask the kernel to get a snapshot :-)
>
> So I can flush out the storage format and two stage process inside qemu,
> and then bother with the kvm/kernel interface.
>
> Normal "bare metal" operation in qemu (or even KVM "PR") doesn't require
> this as in that case the hash table is just a normal part of the guest
> memory, it's only an issue when doing paravirtualized guest such as
> pseries (aka PAPR).
IIRC we still allocate it outside of normal guest memory, so you don't get the
migration for free :).
Alex
- Re: [Qemu-devel] vm state save/restore question, (continued)
- Re: [Qemu-devel] vm state save/restore question, Alexander Graf, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Benjamin Herrenschmidt, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Alexander Graf, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Benjamin Herrenschmidt, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Alexander Graf, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Benjamin Herrenschmidt, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Juan Quintela, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Benjamin Herrenschmidt, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Juan Quintela, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Benjamin Herrenschmidt, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question,
Alexander Graf <=
- Re: [Qemu-devel] vm state save/restore question, Benjamin Herrenschmidt, 2012/06/19
- Re: [Qemu-devel] vm state save/restore question, Alexander Graf, 2012/06/19