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Re: [PATCH 4/5] x86/ucode: Cache results in microcode_scan_module()
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 28 Mar 2023 18:01:18 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 28 Mar 2023 16:01:30 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 28.03.2023 17:12, Andrew Cooper wrote:
> On 28/03/2023 3:19 pm, Jan Beulich wrote:
>> On 27.03.2023 21:41, Andrew Cooper wrote:
>>> Right now, the boot flow depends on the second pass over
>>> bootstrap_map()/find_cpio_data() altering ucode_blob.data to use the
>>> directmap
>>> alias of the CPIO module, where previously it caches the early boostrap
>>> mapping.
>>>
>>> If the scan is successful, it will be successful the second time too, but
>>> there's no point repeating the work. Cache the module index, offset and
>>> size
>>> to short circuit things the second time around.
>> If the scan failed, it will fail the 2nd time too. Maybe deal with
>> this case as well, e.g. by clearing ucode_scan at the end of
>> microcode_scan_module() when nothing was found?
>
> See patch 5. It can only become true then because of how the callers
> are arranged.
Right, I've meanwhile seen you do it there. That's fine. Yet I think it
could also be done earlier (and if I'm not mistaken also ahead of all
of the rearrangements you do).
Jan
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