Re: [PATCH v7 02/17] PCI/DPC: Log Error Source ID only when valid

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Tue, 20 May 2025 16:50:19 -0500
Bjorn Helgaas <helgaas@kernel.org> wrote:

> From: Bjorn Helgaas <bhelgaas@google.com>
> 
> DPC Error Source ID is only valid when the DPC Trigger Reason indicates
> that DPC was triggered due to reception of an ERR_NONFATAL or ERR_FATAL
> Message (PCIe r6.0, sec 7.9.14.5).
> 
> When DPC was triggered by ERR_NONFATAL (PCI_EXP_DPC_STATUS_TRIGGER_RSN_NFE)
> or ERR_FATAL (PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE) from a downstream device,
> log the Error Source ID (decoded into domain/bus/device/function).  Don't
> print the source otherwise, since it's not valid.
> 
> For DPC trigger due to reception of ERR_NONFATAL or ERR_FATAL, the dmesg
> logging changes:
> 
>   - pci 0000:00:01.0: DPC: containment event, status:0x000d source:0x0200
>   - pci 0000:00:01.0: DPC: ERR_FATAL detected
>   + pci 0000:00:01.0: DPC: containment event, status:0x000d, ERR_FATAL received from 0000:02:00.0
> 
> and when DPC triggered for other reasons, where DPC Error Source ID is
> undefined, e.g., unmasked uncorrectable error:
> 
>   - pci 0000:00:01.0: DPC: containment event, status:0x0009 source:0x0200
>   - pci 0000:00:01.0: DPC: unmasked uncorrectable error detected
>   + pci 0000:00:01.0: DPC: containment event, status:0x0009: unmasked uncorrectable error detected
> 
> Previously the "containment event" message was at KERN_INFO and the
> "%s detected" message was at KERN_WARNING.  Now the single message is at
> KERN_WARNING.
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> Tested-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Matches the spec conditions as far as I can tell.

I guess interesting debate on whether providing extra garbage info is
a bug or not. Maybe a fixes tag for this one as well?

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

I briefly wondered if it makes sense to have a prefix string initialized
outside the switch with "containment event, status:%#06x:"
made sense but it's probably not worth the effort and maybe makes it
harder to grep for the error messages.  So in the end
I think your code here is the best option.

Jonathan