Re: [Xen-devel] [PATCH v9 10/15] microcode: split out apply_microcode() from cpu_request_microcode()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.08.2019 05:22, Chao Gao wrote:
> On Thu, Aug 29, 2019 at 12:06:28PM +0200, Jan Beulich wrote:
>> On 22.08.2019 15:59, Roger Pau Monné  wrote:
>>> Seeing how this works I'm not sure what's the best option here. As
>>> updating will be attempted on other CPUs, I'm not sure if it's OK to
>>> return an error if the update succeed on some CPUs but failed on
>>> others.
>>
>> The overall result of a partially successful update should be an
>> error - mismatched ucode may, after all, be more of a problem
>> than outdated ucode.
> 
> Will only take care -EIO case. If systems have differing ucodes on
> cores, partially update is expected when we try to correct the system
> with an ucode equal to the newest ucode rev already on cores.

But an update attempt with what's already loaded in the CPU should
yield "success", hence a "partial" update like what you describe
should not be considered "partial" in the first place. Iirc an
update attempt when same (or newer?) ucode is already loaded on
all cores yields "success" too, doesn't it?

Jan

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