linux-kernel - Re: [PATCH 1/1] PCI/RCEC: Fix failure to inject errors to some RCiEP devices

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Date:   Thu, 18 Feb 2021 23:11:34 +0100
From:   'Krzysztof Wilczyński' <kw@...ux.com>
To:     "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        "Kelley, Sean V" <sean.v.kelley@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>, "Jin, Wen" <wen.jin@...el.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] PCI/RCEC: Fix failure to inject errors to some RCiEP
 devices

Hi Qiuxu,

[...]
> > Agree to simplify the commit message. How about the following subject and commit message?
> > 
> > Subject:  
> > Use device number to check RCiEPBitmap of RCEC
> > 
> > Commit message: 
> > rcec_assoc_rciep() used the combination of device number and function
> > number 'devfn' to check whether the corresponding bit in the
> > RCiEPBimap of RCEC was set. According to [1], it only needs to use the
> > device number to check the corresponding bit in the RCiEPBitmap was
> > set. So fix it by using PCI_SLOT() to convert 'devfn' to device number
> > for rcec_assoc_rciep(). [1] PCIe r5.0, sec "7.9.10.2 Association
> > Bitmap for RCiEPs"
> 
> I took your suggestion and came up with the following:
> 
>   Function rcec_assoc_rciep() incorrectly used "rciep->devfn" (a single
>   byte encoding the device and function number) as the device number to
>   check whether the corresponding bit was set in the RCiEPBitmap of the
>   RCEC (Root Complex Event Collector) while enumerating over each bit of
>   the RCiEPBitmap.
> 
>   As per the PCI Express Base Specification, Revision 5.0, Version 1.0,
>   Section 7.9.10.2, "Association Bitmap for RCiEPs", p. 935, only needs to
>   use a device number to check whether the corresponding bit was set in
>   the RCiEPBitmap.
> 
>   Fix rcec_assoc_rciep() using the PCI_SLOT() macro and convert the value
>   of "rciep->devfn" to a device number to ensure that the RCiEP devices
>   are associated with the RCEC are linked when the RCEC is enumerated.
> 
> Using either of the following as the subject:
> 
>   PCI/RCEC: Use device number to check RCiEPBitmap of RCEC
>   PCI/RCEC: Fix RCiEP capable devices RCEC association
> 
> What do you think?  Also, feel free to change whatever you see fit, of
> course, as tis is only a suggestion.

We could probably add the following:

  Fixes: 507b460f8144 ("PCI/ERR: Add pcie_link_rcec() to associate RCiEPs")

Since this would where the issue was originally introduced.  I forgot to
mention this in the previous message, apologies.

Krzysztof