From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Simon Gaiser <simon@invisiblethingslab.com>,
xen-devel@lists.xenproject.org
Cc: Jan Beulich <jbeulich@suse.com>
Subject: Re: Resume from suspend to RAM broken when using early microcode updates
Date: Wed, 11 Apr 2018 12:51:26 +0100 [thread overview]
Message-ID: <6fbc10ea-d222-94e0-0a60-76cbc6ba1ab2@citrix.com> (raw)
In-Reply-To: <c91218e2-d793-4e1d-343f-c4a566e66b47@invisiblethingslab.com>
On 11/04/18 12:48, Simon Gaiser wrote:
> Hi,
>
> when I use early microcode loading with the microcode update with the
> BTI mitigations, resuming from suspend to RAM is broken.
>
> Based on added logging to enter_state() (from power.c) it doesn't
> survive the local_irq_restore(flags) call (at least a printk() after the
> call doesn't output anything on the serial console).
>
> I guess that some irq handler tries to use IBRS/IBPB. But the microcode
> is only loaded later.
>
> If I simply move the microcode_resume_cpu(0) directly before the
> local_irq_restore(flags) everything seems to work fine. But I'm not sure
> if this has unintended consequences.
>
> I tested the above with Xen 4.8.3 from Qubes which includes the BTI and
> microcode patches from staging-4.8. AFAICS there are no commits which
> changes the affected code or other commits which sound relevant so this
> probably affected also all the newer branches.
S3 support is a very unloved area of the hypervisor.
Yes - we definitely need to get microcode reloaded before interrupts are
enabled. That said, I would have expected a backtrace complaining about
a GP fault if we had hit the use of IBRS/IBPB before the microcode was
reloaded.
~Andrew
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next prev parent reply other threads:[~2018-04-11 11:51 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-11 11:48 Resume from suspend to RAM broken when using early microcode updates Simon Gaiser
2018-04-11 11:51 ` Andrew Cooper [this message]
2018-04-11 12:01 ` Simon Gaiser
2018-04-11 12:11 ` Jan Beulich
2018-04-11 12:17 ` Jan Beulich
2018-04-11 12:46 ` Simon Gaiser
2018-04-11 13:45 ` Jan Beulich
2018-04-11 20:14 ` [PATCH 1/2] x86/microcode: Indicate "not found" in rc of microcode_resume_cpu() Simon Gaiser
2018-04-11 20:14 ` [PATCH 2/2] x86: correct ordering of operations during S3 resume Simon Gaiser
2018-04-11 20:21 ` [PATCH v2 " Simon Gaiser
[not found] ` <5ACE6EA10200005203786DDD@prv1-mh.provo.novell.com>
2018-04-12 7:12 ` Jan Beulich
2018-04-12 6:56 ` [PATCH 1/2] x86/microcode: Indicate "not found" in rc of microcode_resume_cpu() Jan Beulich
2018-04-11 12:12 ` Resume from suspend to RAM broken when using early microcode updates Andrew Cooper
2018-04-11 14:49 ` Konrad Rzeszutek Wilk
2018-04-11 15:05 ` Andrew Cooper
2018-04-11 15:32 ` Jan Beulich
2018-04-11 12:04 ` Jan Beulich
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