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

[Rafael J. Wysocki]

On Mon, Jan 12, 2026 at 12:12 PM Hanjun Guo <guohanjun@xxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>

Applied as 6.20 material, thanks!