From: Borislav Petkov <bp@alien8.de>
To: Jeshua Smith <jeshuas@nvidia.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
"Luck, Tony" <tony.luck@intel.com>,
"james.morse@arm.com" <james.morse@arm.com>,
"keescook@chromium.org" <keescook@chromium.org>,
"gpiccoli@igalia.com" <gpiccoli@igalia.com>,
"lenb@kernel.org" <lenb@kernel.org>,
"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-hardening@vger.kernel.org"
<linux-hardening@vger.kernel.org>,
"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
Thierry Reding <treding@nvidia.com>,
Jonathan Hunter <jonathanh@nvidia.com>
Subject: Re: [PATCH V2] ACPI: APEI: Use ERST timeout for slow devices
Date: Wed, 25 Oct 2023 16:22:45 +0200 [thread overview]
Message-ID: <20231025142245.GHZTkktbRl1wjfNc15@fat_crate.local> (raw)
In-Reply-To: <MN2PR12MB33738FA73A69BC6AEB64BD63DBDEA@MN2PR12MB3373.namprd12.prod.outlook.com>
Hi,
On Wed, Oct 25, 2023 at 02:09:37PM +0000, Jeshua Smith wrote:
<... snip a very detailed and good explanation... >
> Writing 128 nor-flash pages would then take 120us * 128 = 15ms
> typical, or 1800us * 128 = 230.4ms max.
This is perfectly suitable to be in the commit message - it explains in
exact detail why the change is needed.
> Actual use case:
>
> Kernel panic -> Pstore calls APEI's ERST code to write the ~32KB error
> log to persistent store -> ERST code writes the error log to
> nor-flash, which takes more than 1ms to complete. This is expected, as
> communicated by the platform to the OS via the maximum time field in
> the ERST table.
This is actually very important and it justifies the need for that
change even more - you want to flush out the complete panic message to
pstore and not only the first couple of lines.
> ... and therefore the extended (ERST-defined) timeout is only applied
> for implementations that indicate that they are "slow". I assume that
> platforms which bother to set the "slow" bit will also specify actual
> timings, and platforms which don't are OK with the current 1ms
> timeout.
Yap, makes perfect sense to me.
> Does that answer your questions?
Yes, thanks for taking the time to explain this in such a detail and
precisely. I think you should use the main bits of what you wrote here
and add them to the commit message - after this there are no more
questions why this patch is needed, IMO.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2023-10-25 14:23 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-12 22:34 [PATCH V2] ACPI: APEI: Use ERST timeout for slow devices Jeshua Smith
2023-08-04 15:55 ` Jeshua Smith
2023-08-04 16:31 ` Luck, Tony
2023-08-05 1:04 ` Jeshua Smith
2023-08-18 16:50 ` Jeshua Smith
2023-09-11 16:15 ` Jeshua Smith
2023-10-02 16:10 ` Jeshua Smith
2023-10-23 15:45 ` Jeshua Smith
2023-10-24 14:32 ` Rafael J. Wysocki
2023-10-24 15:27 ` Borislav Petkov
2023-10-25 14:09 ` Jeshua Smith
2023-10-25 14:22 ` Borislav Petkov [this message]
2023-10-24 15:24 ` Tony Luck
2023-10-24 18:51 ` Rafael J. Wysocki
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