linux-kernel - Re: [PATCH 3/4] cxl/pci: Register for and process CPER events

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Date: Fri, 1 Mar 2024 13:49:50 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: Ira Weiny <ira.weiny@...el.com>, Dan Williams <dan.j.williams@...el.com>,
	Jonathan Cameron <jonathan.cameron@...wei.com>, Smita Koralahalli
	<Smita.KoralahalliChannabasappa@....com>, Shiju Jose <shiju.jose@...wei.com>
CC: Dan Carpenter <dan.carpenter@...aro.org>, Yazen Ghannam
	<yazen.ghannam@....com>, Davidlohr Bueso <dave@...olabs.net>, Dave Jiang
	<dave.jiang@...el.com>, 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>, Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH 3/4] cxl/pci: Register for and process CPER events

Ira Weiny wrote:
> If the firmware has configured CXL event support to be firmware first
> the OS can process those events through CPER records.  The CXL layer has
> unique DPA to HPA knowledge and standard event trace parsing in place.
> 
> CPER records contain Bus, Device, Function information which can be used
> to identify the PCI device which is sending the event.
> 
> Add a CXL CPER callback to process events through the CXL trace
> subsystem.
> 
> Future patches will provide additional region information such as HPA.
> 
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> 
> ---
> Changes:
> [iweiny: Add back in after the revert in 6.8]
> ---
>  drivers/cxl/pci.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 68 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 2ff361e756d6..6cf8336d1b33 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -974,6 +974,73 @@ static struct pci_driver cxl_pci_driver = {
>  	},
>  };
>  
> -module_pci_driver(cxl_pci_driver);
> +#define CXL_EVENT_HDR_FLAGS_REC_SEVERITY GENMASK(1, 0)
> +static void cxl_cper_event_call(enum cxl_event_type ev_type,
> +				struct cxl_cper_event_rec *rec)
> +{
> +	struct cper_cxl_event_devid *device_id = &rec->hdr.device_id;
> +	struct pci_dev *pdev __free(pci_dev_put) = NULL;
> +	enum cxl_event_log_type log_type;
> +	struct cxl_dev_state *cxlds;
> +	unsigned int devfn;
> +	u32 hdr_flags;
> +
> +	pr_debug("CPER event for device %u:%u:%u.%u\n",
> +		 device_id->segment_num, device_id->bus_num,
> +		 device_id->device_num, device_id->func_num);
> +
> +	devfn = PCI_DEVFN(device_id->device_num, device_id->func_num);
> +	pdev = pci_get_domain_bus_and_slot(device_id->segment_num,
> +					   device_id->bus_num, devfn);
> +	if (!pdev) {
> +		pr_err("CPER event device %u:%u:%u.%u not found\n",
> +			device_id->segment_num, device_id->bus_num,
> +			device_id->device_num, device_id->func_num);
> +		return;
> +	}
> +
> +	dev_dbg(&pdev->dev, "Found device %u:%u.%u\n", device_id->bus_num,
> +		device_id->device_num, device_id->func_num);

These print statements are excessive. The dev_dbg() already encodes the
device BDF into the device name. The pr_err() is not actionable and
somewhat redundant with the default cper_estatus_print_section() print.

I would just delete all of them.