linux-kernel - Re: [PATCH] EDAC/mce_amd: Reduce unnecessary spew in dmesg if SMCA feature bit is not exposed

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Message-ID: <20210615163221.GA2991@aus-x-yghannam.amd.com>
Date:   Tue, 15 Jun 2021 12:32:21 -0400
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        James Morse <james.morse@....com>,
        Robert Richter <rric@...nel.org>
Subject: Re: [PATCH] EDAC/mce_amd: Reduce unnecessary spew in dmesg if SMCA
 feature bit is not exposed

On Tue, Jun 15, 2021 at 06:11:04PM +0200, Borislav Petkov wrote:
> On Tue, Jun 15, 2021 at 12:00:09PM -0400, Yazen Ghannam wrote:
> > So I think we can downgrade this warning to a debug message, if the
> > module stays builtin. And/or we change the default config option to
> > module, and we make sure the module only autoloads in the proper cases.
> > 
> > What do you think?
> 
> I think, as I said before, that we should simply not load this in
> guests. Then this will be taken care of once and for all and we can do
> whatever we want on baremetal, as to what error message to issue and how
> many times to issue it, whether the decoder is builtin or default y or
> yadda yadda.
> 
> Because even if you say in a guest:
> 
> 	pr_warn_once("Decoding supported only on Scalable MCA processors.\n");
> 
> you're kinda misleading because the guest might be an SMCA processor but
> not all features are emulated, including SMCA. So it is not really an
> SMCA processor but some not really existant hybrid or so.
> 
> So since this whole SMCA thing does not apply to virtualization, we
> should simply not load on virt and be done with it.
>

Yes, I agree. I was a bit confused about the X86_FEATURE_HYPERVISOR
thing, but I think I get it. This definitely looks simple to do.

Thanks,
Yazen