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Re: [Xen-devel] [PATCH] x86/microcode: Support builtin CPU microcode
- To: Eslam Elnikety <elnikety@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Tue, 17 Dec 2019 22:44:13 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Wei Liu <wl@xxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Ian Jackson <ian.jackson@xxxxxxxxxxxxx>, Paul Durrant <pdurrant@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, David Woodhouse <dwmw@xxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Tue, 17 Dec 2019 22:44:23 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 17/12/2019 22:41, Eslam Elnikety wrote:
> On 13.12.19 14:57, Andrew Cooper wrote:
>> On 12/12/2019 22:13, Eslam Elnikety wrote:
>>>>> Second, there is often need to couple a Xen build with a minimum
>>>>> microcode patch level. Having the microcode built within the Xen
>>>>> image
>>>>> itself is a streamlined, natural way of achieving that.
>>>>
>>>> Okay, I can accept this as a reason, to some degree at least. Yet
>>>> as said elsewhere, I don't think you want then to override a
>>>> possible "external" ucode module with the builtin blobs. Instead
>>>> the newest of everything that's available should then be loaded.
>>>
>>> Extending Xen to work around tools shortcomings is absolutely not what
>>> I have in mind. I should have started with the second reason. Read
>>> this as: Xen relies on a minimum microcode feature set, and it makes
>>> sense to couple both in one binary. This coupling just happens to
>>> provide an added benefit in the face of tools shortcoming.
>>
>> Do we have anything which strictly relies on a minimum version?
>
> I had in mind microcode speculation mitigation features when reasoning
> with the minimum patch level argument.
Considering how well the first round of speculative microcode went,
mandating it would have been a rather bad thing...
But yes - as a usecase of "I wish to bundle the minimum microcode I'd
like to work with", this seems entirely reasonable.
~Andrew
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