linux-kernel - Re: [PATCH 1/2] x86/microcode: Update late microcode in parallel

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Message-ID: <20190828005630.GB47494@otc-nc-03>
Date:   Tue, 27 Aug 2019 17:56:30 -0700
From:   "Raj, Ashok" <ashok.raj@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Mihai Carabas <mihai.carabas@...cle.com>,
        linux-kernel@...r.kernel.org, boris.ostrovsky@...cle.com,
        konrad.wilk@...cle.com, patrick.colp@...cle.com,
        kanth.ghatraju@...cle.com, Jon.Grimm@....com,
        Thomas.Lendacky@....com, Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCH 1/2] x86/microcode: Update late microcode in parallel

On Tue, Aug 27, 2019 at 02:25:01PM +0200, Borislav Petkov wrote:
> On Mon, Aug 26, 2019 at 01:23:39PM -0700, Raj, Ashok wrote:
> > > Cloud customers have expressed discontent as services disappear for a
> > > prolonged time. The restriction is that only one core goes through the
> > s/one core/one thread of a core/
> > 
> > > update while other cores are quiesced.
> > s/cores/other thread(s) of the core
> 
> Changed it to:
> 
> "Cloud customers have expressed discontent as services disappear for
> a prolonged time. The restriction is that only one core (or only one
> thread of a core in the case of an SMT system) goes through the update
> while other cores (or respectively, SMT threads) are quiesced."

the last line seems to imply that only one core can be updated at a time.
But the only requirement is on a per-core basis, the HT thread sharing
a core must be quiesced while the microcode update is performed. 

for ex. if you have 2 cores, you can update microcode on both cores
at the same time. 

C0T0, C0T1 - If you are updating on C0T0, C0T1 must be waiting for the update
to complete

But You can initiate the microcode update on C1T0 simultaneously. 


> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Good mailing practices for 400: avoid top-posting and trim the reply.