linux-kernel - Re: [PATCH v2] arch/x86: Fix boot_cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 01 Aug 2018 16:16:42 +0200
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     Prarit Bhargava <prarit@...hat.com>
Cc:     bp@...en8.de, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, sironi@...zon.de,
        stable@...r.kernel.org, tony.luck@...el.com
Subject: Re: [PATCH v2] arch/x86: Fix boot_cpu_data.microcode version output

Hi.

On 01.08.2018 13:38, Prarit Bhargava wrote:
>> After this patch, do we preserve an original microcode version 
>> somewhere? If no,
>> why? Sometimes it is useful while debugging another crash because of 
>> faulty
>> microcode.
>> 
> Interesting, and thanks for bringing this up.  Oleksandr, under what
> circumstances would you want to know what the old version was.  AFAICS 
> it is no
> longer running and should not have an impact on the system?

Once the kernel log does not contain a printout regarding updated 
microcode anymore (because the log buffer is limited in size and can be 
overwritten) and once you have a vmcore, it is handy to use 
boot_cpu_data to compare the microcode version with the per-CPU value to 
find out that is was updated at all. Or, maybe, that can be inspected in 
another way now?

-- 
   Oleksandr Natalenko (post-factum)