From: Boris Ostrovsky <email@example.com>
To: Thomas Gleixner <firstname.lastname@example.org>
Cc: Yanmin Zhang <email@example.com>,
Joerg Roedel <firstname.lastname@example.org>,
Peter Zijlstra <email@example.com>,
Ingo Molnar <firstname.lastname@example.org>, Peter Anvin <email@example.com>,
Borislav Petkov <firstname.lastname@example.org>, xiao jin <email@example.com>
Subject: Re: [patch 1/4] hotplug: Prevent alloc/free of irq descriptors during cpu up/down
Date: Tue, 14 Jul 2015 17:07:09 -0400 [thread overview]
Message-ID: <55A579FD.firstname.lastname@example.org> (raw)
On 07/14/2015 04:15 PM, Thomas Gleixner wrote:
> On Tue, 14 Jul 2015, Boris Ostrovsky wrote:
>> On 07/14/2015 01:32 PM, Thomas Gleixner wrote:
>>> On Tue, 14 Jul 2015, Boris Ostrovsky wrote:
>>>> On 07/14/2015 11:44 AM, Thomas Gleixner wrote:
>>>>> On Tue, 14 Jul 2015, Boris Ostrovsky wrote:
>>>>>>> Prevent allocation and freeing of interrupt descriptors accross cpu
>>>>>> This breaks Xen guests that allocate interrupt descriptors in
>>>>> And where exactly does XEN allocate those descriptors?
>>>> There is also a similar pass via xen_cpu_up() -> xen_smp_intr_init()
>>>>>> Any chance this locking can be moved into arch code?
>>> 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
>>>>>> 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.
next prev parent reply other threads:[~2015-07-14 21:08 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 [this message]
[not found] ` <55A579FD.firstname.lastname@example.org>
2016-03-12 9:19 ` Thomas Gleixner
[not found] ` <alpine.DEB.2.11.1603121017500.3657@nanos>
2016-03-14 13:12 ` Boris Ostrovsky
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