linux-kernel - Re: [PATCH 3/4] acpi/ghes, cxl/pci: Trace FW-First CXL Protocol Errors

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Date: Mon, 24 Jun 2024 15:04:30 -0700
From: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
To: Dan Williams <dan.j.williams@...el.com>, linux-efi@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Yazen Ghannam <yazen.ghannam@....com>, Bowman Terry <terry.bowman@....com>
Subject: Re: [PATCH 3/4] acpi/ghes, cxl/pci: Trace FW-First CXL Protocol
 Errors

Hi Dan,

On 6/13/2024 10:47 AM, Smita Koralahalli wrote:
> Hi Dan,
> 
> On 6/11/2024 5:07 PM, Dan Williams wrote:
>> Smita Koralahalli wrote:
>>> When PCIe AER is in FW-First, OS should process CXL Protocol errors from
>>> CPER records.
>>>
>>> Reuse the existing work queue cxl_cper_work registered with GHES to 
>>> notify
>>> the CXL subsystem on a Protocol error.
>>>
>>> The defined trace events cxl_aer_uncorrectable_error and
>>> cxl_aer_correctable_error currently trace native CXL AER errors. Reuse
>>> them to trace FW-First Protocol Errors.
>>>
>>> Signed-off-by: Smita Koralahalli 
>>> <Smita.KoralahalliChannabasappa@....com>
>>> ---
>>>   drivers/acpi/apei/ghes.c  | 14 ++++++++++++++
>>>   drivers/cxl/core/pci.c    | 24 ++++++++++++++++++++++++
>>>   drivers/cxl/cxlpci.h      |  3 +++
>>>   drivers/cxl/pci.c         | 34 ++++++++++++++++++++++++++++++++--
>>>   include/linux/cxl-event.h |  1 +
>>>   5 files changed, 74 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
>>> index 1a58032770ee..a31bd91e9475 100644
>>> --- a/drivers/acpi/apei/ghes.c
>>> +++ b/drivers/acpi/apei/ghes.c
>>> @@ -723,6 +723,20 @@ static void cxl_cper_handle_prot_err(struct 
>>> acpi_hest_generic_data *gdata)
>>>       if (cxl_cper_handle_prot_err_info(gdata, &wd.p_err))
>>>           return;
>>> +
>>> +    guard(spinlock_irqsave)(&cxl_cper_work_lock);
>>> +
>>> +    if (!cxl_cper_work)
>>> +        return;
>>> +
>>> +    wd.event_type = CXL_CPER_EVENT_PROT_ERR;
>>> +
>>> +    if (!kfifo_put(&cxl_cper_fifo, wd)) {
>>> +        pr_err_ratelimited("CXL CPER kfifo overflow\n");
>>> +        return;
>>> +    }
>>> +
>>> +    schedule_work(cxl_cper_work);
>>
>> This seems wrong to unconditionally schedule the cxl_pci driver to look
>> at potentially "non-device" errors. With Terry's upcoming CXL switch
>> port error handling there will be a native path for those errors, but
>> until that arrives, I see no point in this code trying to convey
>> root/switch port errors to the endpoint driver.
> 
> I see okay. What are your recommendations on this? Just confine it to 
> CXL RCD, CXL SLD and CXL LD? And then extend it to ports once Terry 
> sends patches?
> 
> Also, I'm not sure about FMLD. Should we just drop it as of now?
> 

Since, Terry sent his port error handling patches, shall I keep the 
above check as is? That is schedule cxl_pci driver on all device and 
port errors with mention to be rebased on Terry's.

I'm slightly doubtful on FMLD though.

Thanks,
Smita

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