From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>, Chao Gao <chao.gao@intel.com>
Cc: Wei Liu <wei.liu2@citrix.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Brian Woods <brian.woods@amd.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [PATCH v4 2/6] microcode: save all microcodes which pass sanity check
Date: Tue, 15 Jan 2019 15:07:07 +0000 [thread overview]
Message-ID: <32bb57d0-50f2-499d-fbdb-2f2c64e3088e@citrix.com> (raw)
In-Reply-To: <5C0103B202000078002017EC@prv1-mh.provo.novell.com>
On 30/11/2018 09:32, Jan Beulich wrote:
>>>> On 30.11.18 at 08:55, <chao.gao@intel.com> wrote:
>> On Thu, Nov 29, 2018 at 10:22:10AM +0100, Roger Pau Monné wrote:
>>> On Thu, Nov 29, 2018 at 10:40:32AM +0800, Chao Gao wrote:
>>>> On Wed, Nov 28, 2018 at 01:00:14PM +0100, Roger Pau Monné wrote:
>>>>> On Wed, Nov 28, 2018 at 01:34:12PM +0800, Chao Gao wrote:
>>>>>> ... and search caches to find a suitable one when loading.
>>>>> Why do you need to save all of them? You are only going to load a
>>>>> single microcode, so I don't understand the need to cache them all.
>>> I think the above question needs an answer.
>> Out of consideraton for a mixed-family system. Anyway, Since Jan commented
>> that we gave up support of a mixed-family system, we only need to save
>> a single microcode for offlined or hot-plugged cpus.
> Well, there might be slightly more needed than just a single instance.
> This depends on whether same family/model CPUs with different
> stepping and/or different "pf" value can be mixed (and would have
> identical feature flags in their CPUID output).
>
> I may have oversimplified the current state of things: Hotplugging
> a CPU with more capabilities than the boot CPU is generally fine
> afaict. Both you (Intel) and AMD place restrictions on permitted
> mixes iirc, so I don't think we need to support anything beyond
> such restrictions. Being able to run on permitted mixes which are
> not in conflict with our general assumption of there not being any
> CPU in the system with less capabilities than the boot CPU would
> seem desirable.
>
> Andrew, do you have any view or opinion here?
I'm not aware of anything since the P4 which has tolerated a
heterogeneous setup of physical CPUs.
Our current microcode loading doesn't support more than a single patch
per system, and I expect plenty of other things would break if we did
genuinely have a heterogeneous setup, featurewise.
I'd simplify everything and assume that there is only a single valid up
to date patch, and I doubt we'll see any problems.
~Andrew
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next prev parent reply other threads:[~2019-01-15 15:11 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 [this message]
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
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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