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Date:   Tue, 17 Sep 2019 08:46:12 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     "Raj, Ashok" <ashok.raj@intel.com>,
        Johannes Erdfelt <johannes@erdfelt.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Mihai Carabas <mihai.carabas@oracle.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Jon Grimm <Jon.Grimm@amd.com>, kanth.ghatraju@oracle.com,
        konrad.wilk@oracle.com, patrick.colp@oracle.com,
        Tom Lendacky <thomas.lendacky@amd.com>,
        x86-ml <x86@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/microcode: Add an option to reload microcode even if
 revision is unchanged
Message-ID: <20190917064612.GA12174@nazgul.tnic>
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 <20190907003338.GA14807@araj-mobl1.jf.intel.com>
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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.
--