Re: [Xen-devel] [PATCH v5 0/8] improve late microcode loading

[Chao Gao <chao.gao@xxxxxxxxx>]

On Tue, Jan 29, 2019 at 12:31:51PM +0100, Roger Pau Monné wrote:
>On Mon, Jan 28, 2019 at 03:06:42PM +0800, Chao Gao wrote:
>> Changes in this version:
>>  - support parallel microcode updates for all cores (see patch 8)
>>  - Address Roger's comments on the last version.
>> 
>> The intention of this series is to make the late microcode loading
>> more reliable by rendezvousing all cpus in stop_machine context.
>> This idea comes from Ashok. I am porting his linux patch to Xen
>> (see patch 7 for more details).
>> 
>> This series makes three changes:
>>  1. Patch 1-6: introduce a global microcode cache
>>  2. Patch 7: synchronize late microcode loading
>>  3. Patch 8: support parallel microcodes update on different cores
>> 
>> Currently, late microcode loading does a lot of things including
>> parsing microcode blob, checking the signature/revision and performing
>> update. Putting all of them into stop_machine context is a bad idea
>> because of complexity (One issue I observed is memory allocation
>> triggered one assertion in stop_machine context). In order to simplify
>> the load process, I move parsing microcode out of the load process.
>> The microcode blob is parsed and a global microcode cache is built on
>> a single CPU before rendezvousing all cpus to update microcode. Other
>> CPUs just get and load a suitable microcode from the global cache.
>> With this global cache, it is safe to put simplified load process to
>> stop_machine context.
>> 
>> Regarding changes to AMD side, I didn't do any test for them due to
>> lack of hardware. Could you help to test this series on an AMD machine?
>> At least, two basic tests are needed:
>> * do a microcode update after system bootup
>> * don't bring all pCPUs up at bootup by specifying maxcpus option in xen
>>   command line and then do a microcode update and online all offlined
>>   CPUs via 'xen-hptool'.
>> 
>
>Thanks for the series, I think it's a good improvement to current
>microcode loading.
>
>I would like to ask how have you tested the series, I don't seem to
>find any tool in the current tree to load a microcode to Xen. The only
>thing I've found is:
>
>https://lists.xen.org/archives/html/xen-devel/2013-07/txtpyXvYZGRwb.txt
>
>Have you used this tool to test the code?

Yes. I am using this patch with some issues fixed.

Thanks
Chao

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