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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 16:19:27 +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 14:19:45 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 27.03.2023 21:41, Andrew Cooper wrote:
> When microcode_scan_module() is used, it's used twice.
>
> The caching of the bootstrap_map() pointer in ucode_blob.data is buggy for
> multiple reasons and is going to be removed.
As before I'm not convinced of "buggy".
> 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?
Jan
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