linux-kernel - Re: [PATCH] x86/microcode: Add an option to reload microcode even if revision is unchanged

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20190917064612.GA12174@nazgul.tnic>
Date:   Tue, 17 Sep 2019 08:46:12 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "Raj, Ashok" <ashok.raj@...el.com>,
        Johannes Erdfelt <johannes@...felt.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Mihai Carabas <mihai.carabas@...cle.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jon Grimm <Jon.Grimm@....com>, kanth.ghatraju@...cle.com,
        konrad.wilk@...cle.com, patrick.colp@...cle.com,
        Tom Lendacky <thomas.lendacky@....com>,
        x86-ml <x86@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/microcode: Add an option to reload microcode even if
 revision is unchanged

On Tue, Sep 17, 2019 at 08:37:10AM +0200, Thomas Gleixner wrote:
> So what happens if the ucode update "fixes" one of the executed
> instructions on the fly? Is that guaranteed to be safe? There is nothing
> which says so.

You'd expect that when you load microcode on the core, the one thread
does the loading and the other SMT thread is in a holding pattern. That
would be optimal.

Considering the dancing through hoops we're doing to keep all threads
quiesced, I'd be sceptical that is the case...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--