linux-hardening - RE: [PATCH V3] ACPI: APEI: Use ERST timeout for slow devices

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Date: Fri, 27 Oct 2023 22:40:43 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: Jeshua Smith <jeshuas@...dia.com>, "keescook@...omium.org"
	<keescook@...omium.org>, "gpiccoli@...lia.com" <gpiccoli@...lia.com>,
	"rafael@...nel.org" <rafael@...nel.org>, "lenb@...nel.org" <lenb@...nel.org>,
	"james.morse@....com" <james.morse@....com>, "bp@...en8.de" <bp@...en8.de>
CC: "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"treding@...dia.com" <treding@...dia.com>, "jonathanh@...dia.com"
	<jonathanh@...dia.com>
Subject: RE: [PATCH V3] ACPI: APEI: Use ERST timeout for slow devices

> 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: Tony Luck <tony.luck@...el.com>