From: Thomas Gleixner <firstname.lastname@example.org>
To: Boris Ostrovsky <email@example.com>
Cc: Yanmin Zhang <firstname.lastname@example.org>,
Joerg Roedel <email@example.com>,
Peter Zijlstra <firstname.lastname@example.org>,
Ingo Molnar <email@example.com>, Peter Anvin <firstname.lastname@example.org>,
Borislav Petkov <email@example.com>, xiao jin <firstname.lastname@example.org>
Subject: Re: [patch 1/4] hotplug: Prevent alloc/free of irq descriptors during cpu up/down
Date: Sat, 12 Mar 2016 10:19:57 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.11.1603121017500.3657__35041.4192806513$1457774601$gmane$org@nanos> (raw)
On Tue, 14 Jul 2015, Boris Ostrovsky wrote:
> On 07/14/2015 04:15 PM, Thomas Gleixner wrote:
> > > > The issue here is that all architectures need that protection and just
> > > > Xen does irq allocations in cpu_up.
> > > >
> > > > So moving that protection into architecture code is not really an
> > > > option.
> > > >
> > > > > > > Otherwise we will need to have something like arch_post_cpu_up()
> > > > > > > after the lock is released.
> > > > I'm not sure, that this will work. You probably want to do this in the
> > > > cpu prepare stage, i.e. before calling __cpu_up().
> > > For PV guests (the ones that use xen_cpu_up()) it will work either before
> > > or
> > > after __cpu_up(). At least my (somewhat limited) testing didn't show any
> > > problems so far.
> > >
> > > However, HVM CPUs use xen_hvm_cpu_up() and if you read comments there you
> > > will
> > > see that xen_smp_intr_init() needs to be called before native_cpu_up() but
> > > xen_init_lock_cpu() (which eventually calls irq_alloc_descs()) needs to be
> > > called after.
> > >
> > > I think I can split xen_init_lock_cpu() so that the part that needs to be
> > > called after will avoid going into irq core code. And then the rest will
> > > go
> > > into arch_cpu_prepare().
> > I think we should revisit this for 4.3. For 4.2 we can do the trivial
> > variant and move the locking in native_cpu_up() and x86 only. x86 was
> > the only arch on which such wreckage has been seen in the wild, but we
> > should have that protection for all archs in the long run.
> > Patch below should fix the issue.
> Thanks! Most of my tests passed, I had a couple of failures but I will need to
> see whether they are related to this patch.
Did you ever come around to address that irq allocation from within cpu_up()?
I really want to generalize the protection instead of carrying that x86 only
Xen-devel mailing list
next prev parent reply other threads:[~2016-03-12 9:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <email@example.com>
[not found] ` <firstname.lastname@example.org>
2015-07-14 14:39 ` [patch 1/4] hotplug: Prevent alloc/free of irq descriptors during cpu up/down Boris Ostrovsky
[not found] ` <55A51F10.email@example.com>
2015-07-14 15:44 ` Thomas Gleixner
[not found] ` <alpine.DEB.2.11.1507141743150.18576@nanos>
2015-07-14 16:03 ` Boris Ostrovsky
[not found] ` <55A532C2.firstname.lastname@example.org>
2015-07-14 17:32 ` Thomas Gleixner
[not found] ` <alpine.DEB.2.11.1507141901460.18576@nanos>
2015-07-14 20:04 ` Boris Ostrovsky
[not found] ` <55A56B48.email@example.com>
2015-07-14 20:15 ` Thomas Gleixner
[not found] ` <alpine.DEB.2.11.1507142211390.18576@nanos>
2015-07-14 21:07 ` Boris Ostrovsky
[not found] ` <55A579FD.firstname.lastname@example.org>
2016-03-12 9:19 ` Thomas Gleixner [this message]
[not found] ` <alpine.DEB.2.11.1603121017500.3657@nanos>
2016-03-14 13:12 ` Boris Ostrovsky
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).