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

[Roger Pau Monné <royger@xxxxxxxxxxx>]

On Tue, Jan 29, 2019 at 08:11:33PM +0800, Chao Gao wrote:
> 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.

Could you please include it in the next version of the series?

We really need this tool in-tree IMO.

Thanks, Roger.

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