linux-kernel - Re: [PATCH] x86/mce: Handle AMD threshold interrupt storms

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Message-ID: <2025112152-tripod-footbath-80ff@gregkh>
Date: Fri, 21 Nov 2025 08:09:21 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: "Naik, Avadhut" <avadnaik@....com>
Cc: stable@...r.kernel.org, sashal@...nel.org, linux-kernel@...r.kernel.org,
	Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
	Tony Luck <tony.luck@...el.com>,
	Yazen Ghannam <yazen.ghannam@....com>,
	Borislav Petkov <bp@...en8.de>, Qiuxu Zhuo <qiuxu.zhuo@...el.com>,
	Avadhut Naik <avadhut.naik@....com>
Subject: Re: [PATCH] x86/mce: Handle AMD threshold interrupt storms

On Fri, Nov 21, 2025 at 01:04:47AM -0600, Naik, Avadhut wrote:
> 
> 
> On 11/21/2025 00:53, Greg KH wrote:
> > On Thu, Nov 20, 2025 at 09:41:24PM +0000, Avadhut Naik wrote:
> >> From: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> >>
> >> Extend the logic of handling CMCI storms to AMD threshold interrupts.
> >>
> >> Rely on the similar approach as of Intel's CMCI to mitigate storms per CPU and
> >> per bank. But, unlike CMCI, do not set thresholds and reduce interrupt rate on
> >> a storm. Rather, disable the interrupt on the corresponding CPU and bank.
> >> Re-enable back the interrupts if enough consecutive polls of the bank show no
> >> corrected errors (30, as programmed by Intel).
> >>
> >> Turning off the threshold interrupts would be a better solution on AMD systems
> >> as other error severities will still be handled even if the threshold
> >> interrupts are disabled.
> >>
> >> Also, AMD systems currently allow banks to be managed by both polling and
> >> interrupts. So don't modify the polling banks set after a storm ends.
> >>
> >>   [Tony: Small tweak because mce_handle_storm() isn't a pointer now]
> >>   [Yazen: Rebase and simplify]
> >>
> >> Stable backport notes:
> >> 1. Currently, when a Machine check interrupt storm is detected, the bank's
> >> corresponding bit in mce_poll_banks per-CPU variable is cleared by
> >> cmci_storm_end(). As a result, on AMD's SMCA systems, errors injected or
> >> encountered after the storm subsides are not logged since polling on that
> >> bank has been disabled. Polling banks set on AMD systems should not be
> >> modified when a storm subsides.
> >>
> >> 2. This patch is a snippet from the CMCI storm handling patch (link below)
> >> that has been accepted into tip for v6.19. While backporting the patch
> >> would have been the preferred way, the same cannot be undertaken since
> >> its part of a larger set. As such, this fix will be temporary. When the
> >> original patch and its set is integrated into stable, this patch should be
> >> reverted.
> >>
> >> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> >> Signed-off-by: Tony Luck <tony.luck@...el.com>
> >> Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> >> Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
> >> Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
> >> Link: https://lore.kernel.org/20251104-wip-mca-updates-v8-0-66c8eacf67b9@amd.com
> >> Signed-off-by: Avadhut Naik <avadhut.naik@....com>
> >> ---
> >> This is somewhat of a new scenario for me. Not really sure about the
> >> procedure. Hence, haven't modified the commit message and removed the
> >> tags. If required, will rework both.
> >> Also, while this issue can be encountered on AMD systems using v6.8 and
> >> later stable kernels, we would specifically prefer for this fix to be
> >> backported to v6.12 since its LTS.
> > 
> > What is the git commit id of this change in Linus's tree?
> 
> I think it has not yet been merged into mainline's master branch.
> This commit was recently accepted into the tip (5th November).

Then there's nothing we can do about this in the stable tree, please
read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for all about this.

thanks,

greg k-h