linux-kernel - Re: [PATCH v6 5/6] acpi/ghes, cxl/pci: Process CXL CPER Protocol Errors

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Message-ID: <ab7d50b3-4125-4449-bfd2-eb04e76b0010@amd.com>
Date: Wed, 12 Feb 2025 13:04:39 -0800
From: "Koralahalli Channabasappa, Smita"
 <Smita.KoralahalliChannabasappa@....com>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-cxl@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Yazen Ghannam <yazen.ghannam@....com>, Terry Bowman <terry.bowman@....com>
Subject: Re: [PATCH v6 5/6] acpi/ghes, cxl/pci: Process CXL CPER Protocol
 Errors

On 2/3/2025 11:03 AM, Luck, Tony wrote:
> On Thu, Jan 23, 2025 at 08:44:20AM +0000, Smita Koralahalli wrote:
>> When PCIe AER is in FW-First, OS should process CXL Protocol errors from
>> CPER records. Introduce support for handling and logging CXL Protocol
>> errors.
>>
>> The defined trace events cxl_aer_uncorrectable_error and
>> cxl_aer_correctable_error trace native CXL AER endpoint errors. Reuse them
>> to trace FW-First Protocol errors.
>>
>> Since the CXL code is required to be called from process context and
>> GHES is in interrupt context, use workqueues for processing.
>>
>> Similar to CXL CPER event handling, use kfifo to handle errors as it
>> simplifies queue processing by providing lock free fifo operations.
>>
>> Add the ability for the CXL sub-system to register a workqueue to
>> process CXL CPER protocol errors.
>>
>> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
>> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
>> ---
>>   drivers/acpi/apei/ghes.c | 49 ++++++++++++++++++++++++++++++++++++++++
>>   drivers/cxl/core/pci.c   | 36 +++++++++++++++++++++++++++++
>>   drivers/cxl/cxlpci.h     |  5 ++++
>>   drivers/cxl/pci.c        | 46 ++++++++++++++++++++++++++++++++++++-
>>   include/cxl/event.h      | 15 ++++++++++++
>>   5 files changed, 150 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
>> index 4d725d988c43..289e365f84b2 100644
>> --- a/drivers/acpi/apei/ghes.c
>> +++ b/drivers/acpi/apei/ghes.c
>> @@ -674,6 +674,15 @@ static void ghes_defer_non_standard_event(struct acpi_hest_generic_data *gdata,
>>   	schedule_work(&entry->work);
>>   }
>>   
>> +/* Room for 8 entries */
> 
> Any science behind the choice of "8" here? This comment is merely
> stating what the #define is used for, not why 8 was chosen.
> 

The choice of "8" was arbitrary and not based on a specific rationale. 
If there are better heuristics or considerations for determining the 
optimal number of entries, I’d appreciate any suggestions.

Thanks
Smita