linux-kernel - Re: [PATCH] acpi/ghes: add TAINT_MACHINE

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Message-ID: <aGVq6khN+QdqD5Aj@gmail.com>
Date: Wed, 2 Jul 2025 10:22:50 -0700
From: Breno Leitao <leitao@...ian.org>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
	James Morse <james.morse@....com>, Borislav Petkov <bp@...en8.de>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...a.com, kbusch@...nel.org, rmikey@...a.com
Subject: Re: [PATCH] acpi/ghes: add TAINT_MACHINE_CHECK on GHES panic path

On Wed, Jul 02, 2025 at 09:31:30AM -0700, Luck, Tony wrote:
> On Wed, Jul 02, 2025 at 08:39:51AM -0700, Breno Leitao wrote:
> > When a GHES (Generic Hardware Error Source) triggers a panic, add the
> > TAINT_MACHINE_CHECK taint flag to the kernel. This explicitly marks the
> 
> While it might not strictly be a machine check that caused GHES to
> panic, it seems close enough from the available TAINT options.

Right, that was my reasoning as well. There are other cases where
TAINT_MACHINE_CHECK is set when the Hardware is broken.

> So unless someone feels it would be better to create a new TAINT
> flag (TAINT_FATAL_GHES? TAINT_FIRMWARE_REPORTED_FATAL_ERRROR?)
> then this seems OK to me.

Thanks. That brings another topic. I am seeing crashes and warnings that
are only happening after recoverable errors. I.e, there is a GHES
recoverable error, and then machine crashes minutes later. A classical
example is when the PCI downstream port disappear, and recovers later,
re-enumerating everything, which is simply chaotic.

I would like to be able to correlate the crash/warning with a machine
that had a recoverable error. At scale, this improves the kernel
monitoring by a lot.

So, if we go toward using TAINT_FATAL_GHES, can we have two flavors?
TAINT_FATAL_GHES_RECOVERABLE and TAINT_FATAL_GHES_FATAL?

Thanks for the review,
--breno

> Reviewed-by: Tony Luck <tony.luck@...el.com>
> 
> > kernel as tainted due to a machine check event, improving diagnostics
> > and post-mortem analysis. The taint is set with LOCKDEP_STILL_OK to
> > indicate lockdep remains valid.
> > 
> > At large scale deployment, this helps to quickly determin panics that
> > are coming due to hardware failures.
> > 
> > Signed-off-by: Breno Leitao <leitao@...ian.org>
> > ---
> >  drivers/acpi/apei/ghes.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> > index f0584ccad4519..3d44f926afe8e 100644
> > --- a/drivers/acpi/apei/ghes.c
> > +++ b/drivers/acpi/apei/ghes.c
> > @@ -1088,6 +1088,8 @@ static void __ghes_panic(struct ghes *ghes,
> >  
> >  	__ghes_print_estatus(KERN_EMERG, ghes->generic, estatus);
> >  
> > +	add_taint(TAINT_MACHINE_CHECK, LOCKDEP_STILL_OK);
> > +
> >  	ghes_clear_estatus(ghes, estatus, buf_paddr, fixmap_idx);
> >  
> >  	if (!panic_timeout)
> > 
> > ---
> > base-commit: e96ee511c906c59b7c4e6efd9d9b33917730e000
> > change-id: 20250702-add_tain-902925f3eb96
> > 
> > Best regards,
> > --  
> > Breno Leitao <leitao@...ian.org>
> >