From: Ashok Raj <ashok.raj@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "Ashok Raj" <ashok_raj@linux.intel.com>,
"X86 ML" <x86@kernel.org>, "Andrew Cooper" <amc96@srcf.net>,
LKML <linux-kernel@vger.kernel.org>,
"Ștefan Talpalaru" <stefantalpalaru@yahoo.com>,
"Ashok Raj" <ashok.raj@intel.com>
Subject: Re: [PATCH] x86/microcode/AMD: Attempt applying on every logical thread
Date: Tue, 16 Aug 2022 16:51:49 +0000 [thread overview]
Message-ID: <YvvLJZR+8jS7Asnq@araj-dh-work> (raw)
In-Reply-To: <YvuQgx698T5cgF+C@zn.tnic>
On Tue, Aug 16, 2022 at 02:41:39PM +0200, Borislav Petkov wrote:
> On Tue, Aug 16, 2022 at 09:00:14AM +0000, Ashok Raj wrote:
> > A re-application means, you want to apply even if the cpu_rev <= patch.rev
>
> Yes.
I see, so we probably shouldn't remove the rev check completely but just
permit to reload if the rev is equal?
>
> > if cpu_rev is > patch_rev, clearly its ahead?. say BIOS has a newer
> > version than in the initrd image, do we want to replace the BIOS
> > version since we do no revid checks here.
>
> Can you even downgrade the microcode through the MSR?
I'm not sure what is true for AMD.
For Intel's there is a Security Version Number in the signed encrypted part
of the microcode. As long as the new image has SVN >= what the CPU's SVN is
you can update the microcode.
So if a rev2 is loaded, and rev1 is the new MCU, and rev2 and rev1 have the
same SVN, you can go down rev from rev2->rev1 where rev2 > rev1.
Microcode enforcement for rollback protection has been the SVN. Version
number is a SW feel good thing to identifying which image you are running,
not intended for preventing rollback or any security enforcement.
Cheers,
Ashok
next prev parent reply other threads:[~2022-08-16 16:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-14 12:00 [PATCH] x86/microcode/AMD: Attempt applying on every logical thread Borislav Petkov
2022-08-16 9:00 ` Ashok Raj
2022-08-16 12:41 ` Borislav Petkov
2022-08-16 16:51 ` Ashok Raj [this message]
2022-08-17 12:12 ` Ashok Raj
2022-08-17 14:23 ` Borislav Petkov
2022-08-17 15:29 ` Ashok Raj
2022-08-17 18:13 ` Borislav Petkov
2022-08-17 20:58 ` Ashok Raj
2022-08-17 21:56 ` Borislav Petkov
2022-08-18 9:58 ` Ashok Raj
2022-11-05 3:45 ` Ashok Raj
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YvvLJZR+8jS7Asnq@araj-dh-work \
--to=ashok.raj@intel.com \
--cc=amc96@srcf.net \
--cc=ashok_raj@linux.intel.com \
--cc=bp@alien8.de \
--cc=linux-kernel@vger.kernel.org \
--cc=stefantalpalaru@yahoo.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).