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Re: [Qemu-devel] [RFC v2 25/32] vhost+postcopy: Lock around set_mem_tabl
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC v2 25/32] vhost+postcopy: Lock around set_mem_table |
Date: |
Mon, 25 Sep 2017 18:56:38 +0100 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
* Peter Xu (address@hidden) wrote:
> On Thu, Aug 24, 2017 at 08:27:23PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <address@hidden>
> >
> > **HACK - better solution needed **
> > We have the situation where:
> >
> > qemu bridge
> >
> > send set_mem_table
> > map memory
> > a) mark area with UFD
> > send reply with map addresses
> > b) start using
> > c) receive reply
> >
> > As soon as (a) happens qemu might start seeing faults
> > from memory accesses (but doesn't until b); but it can't
> > process those faults until (c) when it's received the
> > mmap addresses.
> >
> > Make the fault handler spin until it gets the reply in (c).
> >
> > At the very least this needs some proper locks, but preferably
> > we need to split the message.
>
> I see discussions about slave channel and ack mechanism in previous
> post. So it's still not adopted (which looks doable)? What's our
> further plan?
Yep I'm going to look at the slave channel stuff.
Dave
> --
> Peter Xu
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
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