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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

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?

Roger.

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