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Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion()
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion() |
Date: |
Wed, 28 Oct 2015 10:58:33 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Pavel Fedin <address@hidden> wrote:
> Hello!
>
>> Applied, thanks.
>
> Thank you.
>
>> I wonder who it has never been needed before. BTW, what is ITS?
>
> ITS is Interrupt Translation Service. It is used by ARM64
> architecture. In a short, it is a special hardware which performs
> table-based lookup of MSI IDs and their destination CPUs, and routes
> them. There can be lots of CPUs and lots of interrupts, so
> these tables are large and are held in a system RAM.
> qemu implementation of this thing needs to be able to flush its
> internal cached state into memory for live migration. This has to
> be done during final stage, right after CPUs have been stopped,
> because right after this point migration code will recheck RAM
> status and send out modified data for the last time.
> The implementation itself has to wait, because the necessary KVM API
> is also not ready yet, but i prefer to upstream as much of the
> infrastructure as possible, because: a) we want to reduce amount of
> out-of-tree patches for our project; b) these things affect qemu
> core code, and upstreaming them makes sure that we do it right, and
> our out-of-tree code will not diverge from the upstream too
> much.
Power people have a similar problem with its hashed page tables, they
integrated their own save_live implementation because they are too big
for the last stage. You can look there for inspiration.
How big are we talking here?
Thanks, Juan.
>
> Kind regards,
> Pavel Fedin
> Expert Engineer
> Samsung Electronics Research center Russia
- [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(), Pavel Fedin, 2015/10/27
- Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(), Juan Quintela, 2015/10/27
- Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(), Pavel Fedin, 2015/10/27
- Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(),
Juan Quintela <=
- Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(), Pavel Fedin, 2015/10/28
- Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(), Pavel Fedin, 2015/10/28
- Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(), Juan Quintela, 2015/10/29
- Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(), Pavel Fedin, 2015/10/29
- Re: [Qemu-devel] [PATCH] migration: Introduce migration_in_completion(), Juan Quintela, 2015/10/29