linux-kernel - Re: [PATCH v3 0/3] ACPI: APEI: GHES: Performance improvements for error notification handlers

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Message-ID: <2a212d70-9752-fecb-a388-d854269a0ff9@huawei.com>
Date: Mon, 12 Jan 2026 19:12:08 +0800
From: Hanjun Guo <guohanjun@...wei.com>
To: Shuai Xue <xueshuai@...ux.alibaba.com>, <tony.luck@...el.com>,
	<mchehab@...nel.org>, <dolinux.peng@...il.com>, <yazen.ghannam@....com>,
	<rafael@...nel.org>
CC: <dave.jiang@...el.com>, <Smita.KoralahalliChannabasappa@....com>,
	<leitao@...ian.org>, <pengdonglin@...omi.com>,
	<baolin.wang@...ux.alibaba.com>, <benjamin.cheatham@....com>, <bp@...en8.de>,
	<dan.j.williams@...el.com>, <james.morse@....com>, <lenb@...nel.org>,
	<linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<zhuo.song@...ux.alibaba.com>
Subject: Re: [PATCH v3 0/3] ACPI: APEI: GHES: Performance improvements for
 error notification handlers

On 2026/1/12 11:22, Shuai Xue wrote:
> changes since v2:
> - Use `guard(rcu)()` instead of explicit `rcu_read_lock()`/`rcu_read_unlock()` per Donglin Peng
> 
> changes since v1:
> - add Tested-by and Reviewed-by tags from Tony
> - change return value from AE_BAD_ADDRESS to -EINVAL ghes_map_error_status per Hanjun
> - remove unnecessary blank lines per Hanjun
> 
> This patch series improves the performance of GHES error notification handlers
> (NMI and SEA) by optimizing how they check for active error conditions.
> 
> Currently, both ghes_notify_nmi() and ghes_notify_sea() perform expensive
> operations on each invocation to determine if there are actual error records
> to process. This includes mapping/unmapping physical addresses and accessing
> hardware registers, which causes significant overhead especially on systems
> with many cores.
> 
> The optimizations introduced in this series:
> 1. Pre-map error status registers during initialization
> 2. Directly check for active errors using mapped virtual addresses
> 3. Extract common functionality into reusable helper functions
> 4. Apply the same optimization to both NMI and SEA handlers
> 
> These changes significantly reduce the overhead of error checking:
> - NMI handler: From ~15,000 TSC cycles to ~900 cycles
> - SEA handler: From 8,138.3 ns to a much faster check
> 
> The initial idea for this optimization came from Tony Luck [1], who identified
> and implemented the approach for the NMI handler. This series extends the
> same concept to the SEA handler and refactors common code into shared helpers.
> 
> Patch 1 (Tony Luck): Improves ghes_notify_nmi() status check by pre-mapping
>                       error status registers and avoiding repeated mappings.
> 
> Patch 2 (Shuai Xue): Extracts common helper functions for error status handling
>                       to eliminate code duplication.
> 
> Patch 3 (Shuai Xue): Applies the same optimization to ghes_notify_sea() to improve
>                       ARMv8 system performance.

Looks good to me, and did a simple compile test on both x86 and arm64
machine,

Reviewed-by: Hanjun Guo <guohanjun@...wei.com>

Thanks
Hanjun