linux-kernel - Re: [PATCH RESEND] PCI/AER: Use a common function to print AER error bits

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Date:   Sat, 28 Apr 2018 12:07:48 -0500
From:   "Alex G." <mr.nuke.me@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        gregkh@...uxfoundation.org, fred@...dlawl.com,
        linux-kernel@...r.kernel.org, alex_gagniuc@...lteam.com,
        austin_bolen@...l.com, keith.busch@...el.com
Subject: Re: [PATCH RESEND] PCI/AER: Use a common function to print AER error
 bits

On 04/28/2018 11:46 AM, Alex G. wrote:
> On 04/27/2018 05:43 PM, Bjorn Helgaas wrote:
>> On Tue, Apr 17, 2018 at 12:09:43PM -0500, Alexandru Gagniuc wrote:
(snip)
>>> +    memset(&info, 0, sizeof(info));
>>> +    info.severity = aer_severity;
>>> +    info.status = status;
>>> +    info.mask = mask;
>>> +    info.first_error = 0x1f;
>>
>> I like this patch a lot, but where does this "first_error = 0x1f" come
>> from?
> 
> aer_(un)correctable_error_string don't go to [0x1f], so this guarantees 
> us we don't print "(First)".
> 
>> I assume this is supposed to be the "First Error Pointer" in the
>> Advanced Error Capabilities and Control register (PCIe r4.0, sec
>> 7.8.4.7).  There is a "cap_control" field in struct
>> aer_capability_regs; should we be using that here?
> 
> There is a way to extract it from the PCI regs, and it's quite simple. 
> IIRC, it should be all f's when the capability is not implemented. I 
> wanted to avoid any further parsing of PCI regs in this patch.

I could update the offending line to say:
  +	info.first_error = PCI_ERR_CAP_FEP(aer->cap_control);

Though I still have the concerns with validating CPER data:

> I can see a way to use even more common printk code, but that requires 
> validating the PCI regs we get from firmware. That means we need to make 
> a guarantee about CPER that is beyond the scope of this patch.
> 
> Alex
>