From: Chao Gao <chao.gao@intel.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Sergey Dyasli <sergey.dyasli@citrix.com>,
Ashok Raj <ashok.raj@intel.com>, WeiLiu <wl@xen.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v7 09/10] microcode: remove microcode_update_lock
Date: Tue, 11 Jun 2019 20:46:04 +0800 [thread overview]
Message-ID: <20190611124604.GB22930@gao-cwp> (raw)
In-Reply-To: <5CF7D77A020000780023598C@prv1-mh.provo.novell.com>
On Wed, Jun 05, 2019 at 08:53:46AM -0600, Jan Beulich wrote:
>>>> On 27.05.19 at 10:31, <chao.gao@intel.com> wrote:
>> microcode_update_lock is to prevent logic threads of a same core from
>> updating microcode at the same time. But due to using a global lock, it
>> also prevented parallel microcode updating on different cores.
>>
>> Remove this lock in order to update microcode in parallel. It is safe
>> because we have already ensured serialization of sibling threads at the
>> caller side.
>> 1.For late microcode update, do_microcode_update() ensures that only one
>> sibiling thread of a core can update microcode.
>> 2.For microcode update during system startup or CPU-hotplug,
>> microcode_mutex() guarantees update serialization of logical threads.
>> 3.get/put_cpu_bitmaps() prevents the concurrency of CPU-hotplug and
>> late microcode update.
>>
>> Note that printk in apply_microcode() and svm_host_osvm_init() (for AMD
>> only) are still processed sequentially.
>>
>> Signed-off-by: Chao Gao <chao.gao@intel.com>
>
>Reviewed-by: Jan Beulich <jbeulich@suse.com>
Thanks.
>
>> ---
>> Changes in v7:
>> - reworked. Remove complex lock logics introduced in v5 and v6. The microcode
>> patch to be applied is passed as an argument without any global variable. Thus
>> no lock is added to serialize potential readers/writers. Callers of
>> apply_microcode() will guarantee the correctness: the patch poninted by the
>> arguments won't be changed by others.
>
>Much better this way indeed.
>
>> @@ -307,8 +303,7 @@ static int apply_microcode(const struct microcode_patch *patch)
>>
>> mc_intel = patch->mc_intel;
>>
>> - /* serialize access to the physical write to MSR 0x79 */
>> - spin_lock_irqsave(µcode_update_lock, flags);
>> + BUG_ON(local_irq_is_enabled());
>>
>> /*
>> * Writeback and invalidate caches before updating microcode to avoid
>
>Thinking about it - what happens if we hit an NMI or #MC here?
>watchdog_disable(), a call to which you add in an earlier patch,
>doesn't really suppress the generation of NMIs, it only tells the
>handler not to look at the accumulated statistics.
I think they should be suppressed. Ashok, could you confirm it?
I will figure out how to suppress them in Xen.
Thanks
Chao
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next prev parent reply other threads:[~2019-06-11 12:42 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-27 8:31 [PATCH v7 00/10] improve late microcode loading Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-05-27 8:31 ` [PATCH v7 01/10] misc/xen-ucode: Upload a microcode blob to the hypervisor Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-04 16:14 ` Andrew Cooper
2019-06-04 16:23 ` Jan Beulich
2019-06-06 2:29 ` Chao Gao
2019-05-27 8:31 ` [PATCH v7 02/10] microcode/intel: extend microcode_update_match() Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-04 14:39 ` Jan Beulich
2019-06-05 13:22 ` Roger Pau Monné
2019-06-05 14:16 ` Jan Beulich
2019-06-06 8:26 ` Chao Gao
2019-06-06 9:01 ` Jan Beulich
2019-05-27 8:31 ` [PATCH v7 03/10] microcode: introduce a global cache of ucode patch Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-04 15:03 ` Jan Beulich
2019-06-10 5:33 ` Chao Gao
2019-06-11 6:50 ` Jan Beulich
2019-05-27 8:31 ` [PATCH v7 04/10] microcode: remove struct ucode_cpu_info Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-04 15:13 ` Jan Beulich
2019-06-10 7:19 ` Chao Gao
2019-05-27 8:31 ` [PATCH v7 05/10] microcode: remove pointless 'cpu' parameter Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-04 15:29 ` Jan Beulich
2019-06-10 7:31 ` Chao Gao
2019-05-27 8:31 ` [PATCH v7 06/10] microcode: split out apply_microcode() from cpu_request_microcode() Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-05 12:37 ` Jan Beulich
2019-06-11 3:32 ` Chao Gao
2019-06-11 7:08 ` Jan Beulich
2019-06-11 8:53 ` Chao Gao
2019-06-11 9:15 ` Jan Beulich
2019-05-27 8:31 ` [PATCH v7 07/10] microcode/intel: Writeback and invalidate caches before updating microcode Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-05 13:20 ` Jan Beulich
2019-05-27 8:31 ` [PATCH v7 08/10] x86/microcode: Synchronize late microcode loading Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-05 14:09 ` Jan Beulich
2019-06-11 12:36 ` Chao Gao
2019-06-11 12:58 ` Jan Beulich
2019-06-11 15:47 ` Raj, Ashok
2019-06-05 14:42 ` Roger Pau Monné
2019-05-27 8:31 ` [PATCH v7 09/10] microcode: remove microcode_update_lock Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-05 14:52 ` Roger Pau Monné
2019-06-05 15:15 ` Jan Beulich
2019-06-05 14:53 ` Jan Beulich
2019-06-11 12:46 ` Chao Gao [this message]
2019-06-11 13:23 ` Jan Beulich
2019-06-11 16:04 ` Raj, Ashok
2019-06-12 7:38 ` Jan Beulich
2019-06-13 14:05 ` Chao Gao
2019-06-13 14:08 ` Jan Beulich
2019-06-13 14:58 ` Chao Gao
2019-06-13 17:47 ` Raj, Ashok
2019-06-14 8:58 ` Jan Beulich
2019-05-27 8:31 ` [PATCH v7 10/10] x86/microcode: always collect_cpu_info() during boot Chao Gao
2019-05-27 8:31 ` [Xen-devel] " Chao Gao
2019-06-05 14:56 ` Roger Pau Monné
2019-06-11 13:02 ` Chao Gao
2019-06-05 15:05 ` Jan Beulich
2019-06-11 12:58 ` Chao Gao
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