linux-kernel - Re: [PATCH] x86/MCE: Prevent CPU offline for SMCA CPUs with non-core banks

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Message-ID: <20240826132057.GA449322@yaz-khff2.amd.com>
Date: Mon, 26 Aug 2024 09:20:57 -0400
From: Yazen Ghannam <yazen.ghannam@....com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	tony.luck@...el.com, x86@...nel.org, avadhut.naik@....com,
	john.allen@....com, boris.ostrovsky@...cle.com
Subject: Re: [PATCH] x86/MCE: Prevent CPU offline for SMCA CPUs with non-core
 banks

On Sun, Aug 25, 2024 at 01:16:37PM +0200, Thomas Gleixner wrote:
> On Wed, Aug 21 2024 at 09:00, Yazen Ghannam wrote:
> > Logical CPUs in AMD Scalable MCA (SMCA) systems can manage non-core
> > banks. Each of these banks represents unique and separate hardware
> > located within the system. Each bank is managed by a single logical CPU;
> > they are not shared. Furthermore, the "CPU to MCA bank" assignment
> > cannot be modified at run time.
> >
> > The MCE subsystem supports run time CPU hotplug. Many vendors have
> > non-core MCA banks, so MCA settings are not cleared when a CPU is
> > offlined for these vendors.
> >
> > Even though the non-core MCA banks remain enabled, MCA errors will not
> > be handled (reported, cleared, etc.) on SMCA systems when the managing
> > CPU is offline.
> >
> > Check if a CPU manages non-core MCA banks and, if so, prevent it from
> > being taken offline.
> 
> Which in turn breaks hibernation and kexec...
>

Right, good point.

Maybe this change can apply only to a user-initiated (sysfs) case?

Thanks,
Yazen