[v3,1/1] PCI/RCEC: Fix RCiEP capable devices RCEC association

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
associated with the RCEC are linked when the RCEC is enumerated.

Fixes: 507b460f8144 ("PCI/ERR: Add pcie_link_rcec() to associate RCiEPs")
Reported-and-tested-by: Wen Jin <wen.jin@intel.com>
Reviewed-by: Sean V Kelley <sean.v.kelley@intel.com>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
---
v2->v3:
 Drop "[ Krzysztof: Update commit message. ]" from the commit message

 drivers/pci/pcie/rcec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Hi Bjorn,

Do you have any comments on this patch? If need any changes, please let me know. 
Thanks!

-Qiuxu

> -----Original Message-----
> From: Zhuo, Qiuxu <qiuxu.zhuo@intel.com>
> Sent: Monday, February 22, 2021 9:17 AM
> To: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Zhuo, Qiuxu <qiuxu.zhuo@intel.com>; Lorenzo Pieralisi
> <lorenzo.pieralisi@arm.com>; Krzysztof Wilczyński <kw@linux.com>; Kelley,
> Sean V <sean.v.kelley@intel.com>; Luck, Tony <tony.luck@intel.com>; Jin, Wen
> <wen.jin@intel.com>; linux-pci@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: [PATCH v3 1/1] PCI/RCEC: Fix RCiEP capable devices RCEC association
> 
> 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 associated
> with the RCEC are linked when the RCEC is enumerated.
> 
> Fixes: 507b460f8144 ("PCI/ERR: Add pcie_link_rcec() to associate RCiEPs")
> Reported-and-tested-by: Wen Jin <wen.jin@intel.com>
> Reviewed-by: Sean V Kelley <sean.v.kelley@intel.com>
> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
> ---
> v2->v3:
>  Drop "[ Krzysztof: Update commit message. ]" from the commit message
> 
>  drivers/pci/pcie/rcec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/rcec.c b/drivers/pci/pcie/rcec.c index
> 2c5c552994e4..d0bcd141ac9c 100644
> --- a/drivers/pci/pcie/rcec.c
> +++ b/drivers/pci/pcie/rcec.c
> @@ -32,7 +32,7 @@ static bool rcec_assoc_rciep(struct pci_dev *rcec, struct
> pci_dev *rciep)
> 
>  	/* Same bus, so check bitmap */
>  	for_each_set_bit(devn, &bitmap, 32)
> -		if (devn == rciep->devfn)
> +		if (devn == PCI_SLOT(rciep->devfn))
>  			return true;
> 
>  	return false;
> --
> 2.17.1

On Mon, Feb 22, 2021 at 09:17:17AM +0800, Qiuxu Zhuo wrote:
> 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
> associated with the RCEC are linked when the RCEC is enumerated.
> 
> Fixes: 507b460f8144 ("PCI/ERR: Add pcie_link_rcec() to associate RCiEPs")
> Reported-and-tested-by: Wen Jin <wen.jin@intel.com>
> Reviewed-by: Sean V Kelley <sean.v.kelley@intel.com>
> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>

I think 507b460f8144 appeared in v5.11, so not something we broke in
v5.12.  Applied to pci/error for v5.13, thanks!

If I understand correctly, we previously only got this right in one
case:

   0 == PCI_SLOT(00.0)    # correct
   1 == PCI_SLOT(00.1)    # incorrect
   2 == PCI_SLOT(00.2)    # incorrect
   ...
   8 == PCI_SLOT(01.0)    # incorrect
   9 == PCI_SLOT(01.1)    # incorrect
   ...
  31 == PCI_SLOT(03.7)    # incorrect

> ---
> v2->v3:
>  Drop "[ Krzysztof: Update commit message. ]" from the commit message
> 
>  drivers/pci/pcie/rcec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/rcec.c b/drivers/pci/pcie/rcec.c
> index 2c5c552994e4..d0bcd141ac9c 100644
> --- a/drivers/pci/pcie/rcec.c
> +++ b/drivers/pci/pcie/rcec.c
> @@ -32,7 +32,7 @@ static bool rcec_assoc_rciep(struct pci_dev *rcec, struct pci_dev *rciep)
>  
>  	/* Same bus, so check bitmap */
>  	for_each_set_bit(devn, &bitmap, 32)
> -		if (devn == rciep->devfn)
> +		if (devn == PCI_SLOT(rciep->devfn))
>  			return true;
>  
>  	return false;
> -- 
> 2.17.1
>

> [...]
> 
> I think 507b460f8144 appeared in v5.11, so not something we broke in v5.12.
> Applied to pci/error for v5.13, thanks!

Thanks Bjorn!

> If I understand correctly, we previously only got this right in one
> case:
> 
>    0 == PCI_SLOT(00.0)    # correct
>    1 == PCI_SLOT(00.1)    # incorrect
>    2 == PCI_SLOT(00.2)    # incorrect
>    ...
>    8 == PCI_SLOT(01.0)    # incorrect
>    9 == PCI_SLOT(01.1)    # incorrect
>    ...
>   31 == PCI_SLOT(03.7)    # incorrect

Yes, you're right. 

Thanks!
-Qiuxu