linux-kernel - Re: [PATCH V3] ACPI: APEI: Use ERST timeout for slow devices

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Message-ID: <20231028110604.GCZTzrHKnsDB+Dmljr@fat_crate.local>
Date:   Sat, 28 Oct 2023 13:06:04 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Jeshua Smith <jeshuas@...dia.com>
Cc:     keescook@...omium.org, tony.luck@...el.com, gpiccoli@...lia.com,
        rafael@...nel.org, lenb@...nel.org, james.morse@....com,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-tegra@...r.kernel.org,
        treding@...dia.com, jonathanh@...dia.com
Subject: Re: [PATCH V3] ACPI: APEI: Use ERST timeout for slow devices

On Fri, Oct 27, 2023 at 10:33:09PM +0000, Jeshua Smith wrote:
> Slow devices such as flash may not meet the default 1ms timeout value,
> so use the ERST max execution time value as the timeout if it is larger
> and if the ERST has the "slow" attribute set.
> 
> Example:
> A NOR flash spec lists "Page program time (256 bytes)" as 120us typical,
> and 1800us max. A 32KB error log would be (32K/256) = 128 nor-flash
> pages. Writing those 128 nor-flash pages would then take
> 120us * 128 = 15ms typical, or 1800us * 128 = 230.4ms max.
> 
> Without this change, when pstore calls APEI's ERST code to write a 32KB
> error log to the NOR flash in the example, the code will flag a timeout
> after 1ms and return an error to pstore. With this change, unless the
> max time value from the ERST table is exceeded, the code will not flag a
> timeout and will return success to pstore after the operation completes.
> 
> Signed-off-by: Jeshua Smith <jeshuas@...dia.com>
> ---

Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette