Re: [PATCH v3 1/2] acpi/ghes: Process CXL Component Events

[Dan Williams <dan.j.williams@intel.com>]

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].
> 
> [0]
> Link: https://lore.kernel.org/all/cover.1711598777.git.alison.schofield@intel.com/
> [1]
> Link: https://lore.kernel.org/all/65d111eb87115_6c745294ac@dwillia2-xfh.jf.intel.com.notmuch/
> [2]
> Link: https://lore.kernel.org/all/b963c490-2c13-4b79-bbe7-34c6568423c7@moroto.mountain/

Like I mentioned last time, perhaps Dave can reformat these lines on
applying to:

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]

Other than that, this looks good to me:

Reviewed-by: Dan Williams <dan.j.williams@intel.com>