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

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Message-ID: <20240429172418.0000534c@Huawei.com>
Date: Mon, 29 Apr 2024 17:24:18 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Ira Weiny <ira.weiny@...el.com>
CC: Dave Jiang <dave.jiang@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Smita Koralahalli
	<Smita.KoralahalliChannabasappa@....com>, Shiju Jose <shiju.jose@...wei.com>,
	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 Fri, 26 Apr 2024 20:34:00 -0700
Ira Weiny <ira.weiny@...el.com> 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>
Totally trivial comment inline.  Maybe Dave can tweak whilst applying...


Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> diff --git a/include/linux/cxl-event.h b/include/linux/cxl-event.h
> index 03fa6d50d46f..a0067c49e2ca 100644
> --- a/include/linux/cxl-event.h
> +++ b/include/linux/cxl-event.h
> @@ -3,6 +3,8 @@
>  #ifndef _LINUX_CXL_EVENT_H
>  #define _LINUX_CXL_EVENT_H
>  
> +#include <linux/workqueue_types.h>
> +
>  /*
>   * Common Event Record Format
>   * CXL rev 3.0 section 8.2.9.2.1; Table 8-42
> @@ -140,4 +142,29 @@ struct cxl_cper_event_rec {
>  	union cxl_event event;
>  } __packed;
>  
> +struct cxl_cper_work_data {
> +	enum cxl_event_type event_type;
> +	struct cxl_cper_event_rec rec;
> +};
> +
> +#ifdef CONFIG_ACPI_APEI_GHES
> +int cxl_cper_register_work(struct work_struct *work);
> +int cxl_cper_unregister_work(struct work_struct *work);
> +int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd);
> +#else
> +static inline int cxl_cper_register_work(struct work_struct *work);
> +{
> +	return 0;
> +}
> +
> +static inline int cxl_cper_unregister_work(struct work_struct *work);
> +{
> +	return 0;
> +}

Trivial note of the day: Inconsistent spacing - add a blank line here.

> +static inline int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd)
> +{
> +	return 0;
> +}
> +#endif
> +
>  #endif /* _LINUX_CXL_EVENT_H */
>