linux-kernel - Re: [PATCH v4 1/2] acpi/ghes: Process CXL Component Events

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Date: Tue, 30 Apr 2024 23:36:49 -0700
From: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
To: Ira Weiny <ira.weiny@...el.com>, Dave Jiang <dave.jiang@...el.com>,
 Dan Williams <dan.j.williams@...el.com>,
 Jonathan Cameron <jonathan.cameron@...wei.com>,
 Shiju Jose <shiju.jose@...wei.com>
Cc: Dan Carpenter <dan.carpenter@...aro.org>,
 Yazen Ghannam <yazen.ghannam@....com>, Davidlohr Bueso <dave@...olabs.net>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ard Biesheuvel <ardb@...nel.org>,
 linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-cxl@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
 Tony Luck <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v4 1/2] acpi/ghes: Process CXL Component Events

On 4/26/2024 8:34 PM, Ira Weiny wrote:
> BIOS can configure memory devices as firmware first.  This will send CXL
> events to the firmware instead of the OS.  The firmware can then inform
> the OS of these events via UEFI.
> 
> UEFI v2.10 section N.2.14 defines a Common Platform Error Record (CPER)
> format for CXL Component Events.  The format is mostly the same as the
> CXL Common Event Record Format.  The difference lies in the use of a
> GUID as the CPER Section Type which matches the UUID defined in CXL 3.1
> Table 8-43.
> 
> Currently a configuration such as this will trace a non standard event
> in the log omitting useful details of the event.  In addition the CXL
> sub-system contains additional region and HPA information useful to the
> user.[0]
> 
> The CXL code is required to be called from process context as it needs
> to take a device lock.  The GHES code may be in interrupt context.  This
> complicated the use of a callback.  Dan Williams suggested the use of
> work items as an atomic way of switching between the callback execution
> and a default handler.[1]
> 
> The use of a kfifo simplifies queue processing by providing lock free
> fifo operations.  cxl_cper_kfifo_get() allows easier management of the
> kfifo between the ghes and cxl modules.
> 
> CXL 3.1 Table 8-127 requires a device to have a queue depth of 1 for
> each of the four event logs.  A combined queue depth of 32 is chosen to
> provide room for 8 entries of each log type.
> 
> Add GHES support to detect CXL CPER records.  Add the ability for the
> CXL sub-system to register a work queue to process the events.
> 
> This patch adds back the functionality which was removed to fix the
> report by Dan Carpenter[2].
> 
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: Rafael J. Wysocki <rafael@...nel.org>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Suggested-by: Dan Carpenter <dan.carpenter@...aro.org>
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Link: http://lore.kernel.org/r/cover.1711598777.git.alison.schofield@intel.com [0]
> Link: http://lore.kernel.org/r/65d111eb87115_6c745294ac@dwillia2-xfh.jf.intel.com.notmuch [1]
> Link: http://lore.kernel.org/r/b963c490-2c13-4b79-bbe7-34c6568423c7@moroto.mountain [2]
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> ---

Sorry, I couldn't get a chance to follow up with all revisions. But 
tested this and it looks good to me.

Tested-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>