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Re: [Xen-devel] [PATCH v9 00/15] improve late microcode loading

On Thu, Aug 22, 2019 at 08:51:43AM +0100, Sergey Dyasli wrote:
>Hi Chao,
>On 19/08/2019 02:25, Chao Gao wrote:
>> Previous change log:
>> Changes in version 8:
>>  - block #NMI handling during microcode loading (Patch 16)
>>  - Don't assume that all CPUs in the system have loaded a same ucode.
>>  So when parsing a blob, we attempt to save a patch as long as it matches
>>  with current cpu signature regardless of the revision of the patch.
>>  And also for loading, we only require the patch to be loaded isn't old
>>  than the cached one.
>>  - store an update after the first successful loading on a CPU
>>  - remove the patch that calls wbinvd() unconditionally before microcode>  
>> loading. It is under internal discussion.
>I noticed that you removed the patch which adds wbinvd() back in v8.
>What was the reasoning behind that and is there any outcome from the
>internal discussion that you mention here?

Jan (maybe someone else) was concerned about the impact of calling
wbinvd() unconditionally, especially with your work to make serial
ucode loading an option. To address this concern, I planned to call
wbinvd() conditionally. I need to confirm with Intel microcode team
whether it is fine and what the condition should be. But I haven't
received an answer. I will talk with Ashok again and probably add
this patch back in v10.


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