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

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Message-ID: <2025112144-wizard-upcountry-292d@gregkh>
Date: Fri, 21 Nov 2025 07:53:55 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Avadhut Naik <avadhut.naik@....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>
Subject: Re: [PATCH] x86/mce: Handle AMD threshold interrupt storms

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?