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Re: [Qemu-devel] [RFC v2 25/32] vhost+postcopy: Lock around set_mem_tabl
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [RFC v2 25/32] vhost+postcopy: Lock around set_mem_table |
Date: |
Wed, 30 Aug 2017 14:50:02 +0800 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
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?
--
Peter Xu
- [Qemu-devel] [RFC v2 19/32] vhost+postcopy: Resolve client address, (continued)
- [Qemu-devel] [RFC v2 19/32] vhost+postcopy: Resolve client address, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 20/32] postcopy: wake shared, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 21/32] postcopy: postcopy_notify_shared_wake, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 22/32] vhost+postcopy: Add vhost waker, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 23/32] vhost+postcopy: Call wakeups, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 24/32] vub+postcopy: madvises, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 25/32] vhost+postcopy: Lock around set_mem_table, Dr. David Alan Gilbert (git), 2017/08/24
- Re: [Qemu-devel] [RFC v2 25/32] vhost+postcopy: Lock around set_mem_table,
Peter Xu <=
- [Qemu-devel] [RFC v2 26/32] vhost: Add VHOST_USER_POSTCOPY_END message, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 27/32] vhost+postcopy: Wire up POSTCOPY_END notify, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 28/32] postcopy: Allow shared memory, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 29/32] vhost-user: Claim support for postcopy, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 30/32] vhost: Merge neighbouring hugepage regions where appropriate, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 31/32] vhost: Don't break merged regions on small remove/non-adds, Dr. David Alan Gilbert (git), 2017/08/24