From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Borislav Petkov <bp@suse.de>,
Wei Liu <wei.liu2@citrix.com>, Ashok Raj <ashok.raj@intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Jun Nakajima <jun.nakajima@intel.com>,
xen-devel <xen-devel@lists.xenproject.org>,
tglx@linutronix.de, Roger Pau Monne <roger.pau@citrix.com>,
Chao Gao <chao.gao@intel.com>
Subject: Re: [PATCH v4 6/6] x86/microcode: Synchronize late microcode loading
Date: Fri, 30 Nov 2018 11:49:14 -0500 [thread overview]
Message-ID: <f8931bc8-4f45-2526-9d2b-b4d668834750@oracle.com> (raw)
In-Reply-To: <5C0106FB020000780020182A@prv1-mh.provo.novell.com>
On 11/30/18 4:46 AM, Jan Beulich wrote:
>>>> On 29.11.18 at 23:43, <boris.ostrovsky@oracle.com> wrote:
>> One other comment about this patch (which IIRC was raised by Andrew on
>> an earlier version) is that it may be worth to stop timer calibration. I
>> am pretty sure we've seen deadlocks, which is why we ended up disabling
>> it during microcode updates.
> I recall the claim, but I don't think I've ever seen proof.
I can't provide proof at this point, only somewhat vague memory of
seeing calibration code in the stack dump.
> My point was
> ans still is that if there's a problem with ucode loading using the
> stop-machine logic here, then there's a problem with the stop-machine
> logic in general, which would make other uses, perhaps most notably
> rcu_barrier(), unsafe too.
Possibly.
rcu_barrier() appears to be only used in cpu hotplug code and power
management, and I don't know whether either has been tested under stress.
In our case it would take multiple microcode updates on relatively large
(~100 cpus) systems before we'd hit the deadlock.
> Otoh from your reply it's not clear whether
> the observed issue wasn't with our present way of loading ucode,
> but then it would put under question the general correctness of
> continue_hypercall_on_cpu(), which again we use for more than just
> ucode loading.
It was with a variation of this new code, not with what's currently in
the tree.
-boris
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next prev parent reply other threads:[~2018-11-30 16:47 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-28 5:34 [PATCH v4 0/6] improve late microcode loading Chao Gao
2018-11-28 5:34 ` [PATCH v4 1/6] microcode/intel: extend microcode_update_match() Chao Gao
2018-11-28 10:58 ` Roger Pau Monné
2018-11-29 2:00 ` Chao Gao
2018-11-29 9:14 ` Roger Pau Monné
2018-11-28 5:34 ` [PATCH v4 2/6] microcode: save all microcodes which pass sanity check Chao Gao
2018-11-28 12:00 ` Roger Pau Monné
2018-11-29 2:40 ` Chao Gao
2018-11-29 9:22 ` Roger Pau Monné
2018-11-30 7:55 ` Chao Gao
2018-11-30 9:32 ` Jan Beulich
2019-01-15 15:07 ` Andrew Cooper
2018-12-04 22:39 ` Woods, Brian
2018-12-05 7:38 ` Chao Gao
2018-11-29 10:19 ` Jan Beulich
2019-01-15 15:15 ` Andrew Cooper
2018-11-28 5:34 ` [PATCH v4 3/6] microcode: delete 'mc' field from struct ucode_cpu_info Chao Gao
2018-11-28 12:32 ` Roger Pau Monné
2018-11-28 5:34 ` [PATCH v4 4/6] microcode: don't call apply_microcode() in cpu_request_microcode() Chao Gao
2018-11-28 15:02 ` Roger Pau Monné
2018-11-29 4:28 ` Chao Gao
2018-11-29 9:46 ` Roger Pau Monné
2018-11-30 8:57 ` Chao Gao
2018-11-30 9:38 ` Jan Beulich
2018-11-28 5:34 ` [PATCH v4 5/6] microcode: delete microcode pointer and size from microcode_info Chao Gao
2018-11-28 15:04 ` Roger Pau Monné
2018-11-28 5:34 ` [PATCH v4 6/6] x86/microcode: Synchronize late microcode loading Chao Gao
2018-11-28 15:22 ` Roger Pau Monné
2018-11-29 4:43 ` Chao Gao
2018-11-29 9:56 ` Roger Pau Monné
2018-11-29 22:43 ` Boris Ostrovsky
2018-11-30 9:46 ` Jan Beulich
2018-11-30 16:49 ` Boris Ostrovsky [this message]
2018-11-30 9:01 ` Chao Gao
2019-01-15 15:24 ` Andrew Cooper
2019-01-15 16:24 ` Roger Pau Monné
2018-12-11 17:01 ` Jan Beulich
2018-12-11 18:16 ` Raj, Ashok
2018-12-12 7:26 ` Jan Beulich
2018-12-13 2:10 ` Boris Ostrovsky
2018-12-12 4:53 ` Chao Gao
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