linux-kernel - Re: [PATCH v3 0/9] Parallel CPU bringup for x86

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Message-ID: <bc3f2b1332c4bb77558df8aa36493a55542fe5b9.camel@infradead.org>
Date:   Wed, 01 Jun 2022 09:30:00 +0100
From:   David Woodhouse <dwmw2@...radead.org>
To:     Tom Lendacky <thomas.lendacky@....com>, Mimoja <mimoja@...oja.de>,
        Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rcu@...r.kernel.org, hewenliang4@...wei.com, hushiyuan@...wei.com,
        luolongjun@...wei.com, hejingxian@...wei.com
Subject: Re: [PATCH v3 0/9] Parallel CPU bringup for x86_64

On Fri, 2022-04-22 at 16:19 -0500, Tom Lendacky wrote:
> On 4/21/22 05:00, Mimoja wrote:
> > Dear Paul,
> > 
> > > Sorry for replying so late. I saw your v4 patches, and tried commit 
> > > 5e3524d21d2a () from your branch `parallel-5.17-part1`. Unfortunately, 
> > > the boot problem still persists on an AMD Ryzen 3 2200 g system, I 
> > > tested with. Please tell, where I should report these results too (here 
> > > or posted v4 patches).
> > 
> > We have confirmed the issue on multiple AMD CPUs from multiple 
> > generations, leading to the guess that only Zen and Zen+ CPU seem affected 
> > with Zen3 and Zen2 (only tested ulv) working fine. Tho we struggled to get 
> > any output as the failing machines just go silent.
> > 
> > Not working:
> > 
> > Ryzen 5 Pro 2500u and 7 2700U
> > Ryzen 3 2300G
> > 
> > while e.g.
> > 
> > Ryzen 7 Pro 4750U
> > Ryzen 9 5950X
> > 
> > both work fine. We will continue to investigate the issue but are 
> > currently a bit pulled into other topics.
> > 
> > Thomas, could please maybe help us identify which CPUs and MC-Versions are 
> > worth looking at? David suggested you might have a good overview here.
> 
> Sorry, but not knowing what the actual reason for the boot problem, I 
> really couldn't give you an idea as to which CPUs and/or MC versions are 
> appropriate to look at.


Well, that's kind of the point... we don't *know* what the problem is.
We think we've eliminated the software concurrency issues, and it seems
like the hardware just dies if you happen to bring up the CPUs 'too
fast'.

If we could get you to reproduce it in a lab and help  work out what's
going on, it would be much appreciated!


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