linux-kernel - Re: [PATCH v3 7/7] acpi/ghes, cxl/pci: Process CXL CPER Protocol Errors

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Message-ID: <e27d3940-c6da-42c5-b6b3-60ee9680331b@amd.com>
Date: Fri, 6 Dec 2024 08:29:05 -0800
From: "Koralahalli Channabasappa, Smita"
 <Smita.KoralahalliChannabasappa@....com>
To: Ira Weiny <ira.weiny@...el.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.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>,
 Dan Williams <dan.j.williams@...el.com>,
 Yazen Ghannam <yazen.ghannam@....com>, Terry Bowman <terry.bowman@....com>
Subject: Re: [PATCH v3 7/7] acpi/ghes, cxl/pci: Process CXL CPER Protocol
 Errors


On 12/2/2024 10:48 AM, Ira Weiny wrote:
> Smita Koralahalli wrote:
>> On 11/26/2024 8:05 AM, Jonathan Cameron wrote:
>>> On Tue, 19 Nov 2024 00:39:15 +0000
>>> Smita Koralahalli <Smita.KoralahalliChannabasappa@....com> 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, while
>>>> cxl_cper_trace_corr_prot_err and cxl_cper_trace_uncorr_prot_err
>>>> trace native CXL AER port errors. Reuse both sets 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>
>>>
>>> A few minor comments inline.
>>>
>>> Thanks
>>>
>>> Jonathan
>>>
>>>> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
>>>> index 4ede038a7148..c992b34c290b 100644
>>>> --- a/drivers/cxl/core/pci.c
>>>> +++ b/drivers/cxl/core/pci.c
>>>> @@ -650,6 +650,56 @@ void read_cdat_data(struct cxl_port *port)
>>>>    }
>>>>    EXPORT_SYMBOL_NS_GPL(read_cdat_data, CXL);
>>>>    
>>>> +void cxl_cper_trace_corr_prot_err(struct pci_dev *pdev, bool flag,
>>>> +				  struct cxl_ras_capability_regs ras_cap)
>>>> +{
>>>> +	struct cxl_dev_state *cxlds;
>>>> +	u32 status;
>>>> +
>>>> +	status = ras_cap.cor_status & ~ras_cap.cor_mask;
>>>> +
>>>> +	if (!flag) {
>>>
>>> As below. Name of flag is not very helpful when reading the code.
>>> Perhaps we can rename?
>>
>> Okay. May be flag -> is_device_error ?
> 
> I had the same question about 'flag'.
> 
>>>
>>>> +		trace_cxl_port_aer_correctable_error(&pdev->dev, status);
>>>> +		return;
>>>> +	}
>>>> +
>>>> +	cxlds = pci_get_drvdata(pdev);
>>>> +	if (!cxlds)
>>>> +		return;
>>>> +
>>>> +	trace_cxl_aer_correctable_error(cxlds->cxlmd, status);
>>>> +}
>>>> +EXPORT_SYMBOL_NS_GPL(cxl_cper_trace_corr_prot_err, CXL);
>>>> +
>>>> +void cxl_cper_trace_uncorr_prot_err(struct pci_dev *pdev, bool flag,
>>>> +				    struct cxl_ras_capability_regs ras_cap)
>>>> +{
>>>> +	struct cxl_dev_state *cxlds;
>>>> +	u32 status, fe;
>>>> +
>>>> +	status = ras_cap.uncor_status & ~ras_cap.uncor_mask;
>>>> +
>>>> +	if (hweight32(status) > 1)
>>>> +		fe = BIT(FIELD_GET(CXL_RAS_CAP_CONTROL_FE_MASK,
>>>> +				   ras_cap.cap_control));
>>>> +	else
>>>> +		fe = status;
>>>> +
>>>> +	if (!flag) {
>>>
>>> Why does  a bool named flag indicate it's a port error?
>>
>> I will rename it.
>>
>> Or may be use an enum to explicitly define the error type
>> (CXL_ERROR_TYPE_DEVICE and CXL_ERROR_TYPE_PORT).
>>
>> Or may be split the function into two distinct ones, one for port errors
>> and one for device errors.
> 
> I would vote for 2 functions.
> Ira

Noted. Thanks!

Thanks
Smita