linux-kernel - Re: [PATCH 1/2] sched: add virt sched domain for the guest

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 23 May 2012 10:48:34 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Liu ping fan <kernelfans@...il.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	qemu-devel@...gnu.org, Ingo Molnar <mingo@...hat.com>,
	Avi Kivity <avi@...hat.com>,
	Anthony Liguori <anthony@...emonkey.ws>
Subject: Re: [PATCH 1/2] sched: add virt sched domain for the guest

On Wed, 2012-05-23 at 16:34 +0800, Liu ping fan wrote:
> so we need to migrate some of vcpus from node-B to node-A, or to
> node-C.

This is absolutely broken, you cannot do that.

A guest task might want to be node affine, it looks at the topology sets
a cpu affinity mask and expects to stay on that node.

But then you come along, and flip one of those cpus to another node. The
guest task will now run on another node and get remote memory accesses.

Similarly for the guest kernel, it assumes cpu:node maps are static, it
will use this for all kinds of things, including the allocation of
per-cpu memory to be node affine to that cpu.

If you go migrate cpus across nodes everything comes down.

Please go do something else, I'll do this.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/