Re: [PATCH 2/2] pci: Expose offset, stride, and VF device ID via sysfs

["Sironi, Filippo" <sironi@amazon.de>]

> On 3. Oct 2017, at 21:48, Bjorn Helgaas <helgaas@kernel.org> wrote:
> 
> On Tue, Oct 03, 2017 at 02:31:14PM -0500, Bjorn Helgaas wrote:
>> On Fri, Sep 29, 2017 at 07:53:31AM +0000, Sironi, Filippo wrote:
>>> 
>>> Hi Bjorn,
>>> 
>>>> On 25. Sep 2017, at 20:55, Bjorn Helgaas <helgaas@kernel.org> wrote:
>>>> 
>>>> Hi Filippo,
>>>> 
>>>> On Mon, Aug 28, 2017 at 03:38:50PM +0200, Filippo Sironi wrote:
>>>>> +static ssize_t sriov_vf_did_show(struct device *dev,
>>>>> +				 struct device_attribute *attr,
>>>>> +				 char *buf)
>>>>> +{
>>>>> +	struct pci_dev *pdev = to_pci_dev(dev);
>>>>> +
>>>>> +	return sprintf(buf, "%x\n", pdev->sriov->vf_did);
>>>>> +}
>>>> 
>>>> What does the vf_did part look like in sysfs?  Do we have a directory with
>>>> both "device" and "vf_did" in it?  If so, why do we have both and do we
>>>> need both?  Could we put the vf_did in the "device" file?
>>> 
>>> On my machine:
>>> 
>>> /sys/bus/pci/devices/0000:03:00.0# ls -l  # this is the PF
>>> total 0
>>> -rw-r--r-- 1 root root    4096 Sep 28 19:41 broken_parity_status
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 class
>>> -rw-r--r-- 1 root root    4096 Sep 28 19:41 config
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 consistent_dma_mask_bits
>>> -rw-r--r-- 1 root root    4096 Sep 28 19:41 d3cold_allowed
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 device
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 dma_mask_bits
>>> lrwxrwxrwx 1 root root       0 Sep 28 19:41 driver -> ../../../../bus/pci/drivers/igb
>>> -rw-r--r-- 1 root root    4096 Sep 28 19:41 driver_override
>>> -rw-r--r-- 1 root root    4096 Sep 28 19:41 enable
>>> lrwxrwxrwx 1 root root       0 Sep 28 19:41 firmware_node -> ../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:4b/device:4c
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 irq
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 local_cpulist
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 local_cpus
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 modalias
>>> -rw-r--r-- 1 root root    4096 Sep 28 19:41 msi_bus
>>> drwxr-xr-x 2 root root       0 Sep 29 09:44 msi_irqs
>>> drwxr-xr-x 3 root root       0 Sep 28 19:41 net
>>> -rw-r--r-- 1 root root    4096 Sep 28 19:41 numa_node
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 offset  # this is new
>>> drwxr-xr-x 2 root root       0 Sep 28 19:41 power
>>> drwxr-xr-x 3 root root       0 Sep 28 19:41 ptp
>>> --w--w---- 1 root root    4096 Sep 28 19:41 remove
>>> --w--w---- 1 root root    4096 Sep 28 19:41 rescan
>>> --w------- 1 root root    4096 Sep 28 19:41 reset
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 resource
>>> -rw------- 1 root root  131072 Sep 28 19:41 resource0
>>> -rw------- 1 root root 4194304 Sep 28 19:41 resource1
>>> -rw------- 1 root root      32 Sep 28 19:41 resource2
>>> -rw------- 1 root root   16384 Sep 28 19:41 resource3
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 revision
>>> -rw-rw-r-- 1 root root    4096 Sep 29 09:44 sriov_numvfs
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 sriov_totalvfs
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 stride  # this is new
>>> lrwxrwxrwx 1 root root       0 Sep 28 19:41 subsystem -> ../../../../bus/pci
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 subsystem_device
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 subsystem_vendor
>>> -rw-r--r-- 1 root root    4096 Sep 28 19:41 uevent
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 vendor
>>> -r--r--r-- 1 root root    4096 Sep 28 19:41 vf_did  # this is new
>>> lrwxrwxrwx 1 root root       0 Sep 29 09:44 virtfn0 -> ../0000:03:10.0
>>> 
>>> nothing changes on for VFs.
>>> Then:
>>> 
>>> /sys/bus/pci/devices/0000:03:00.0# cat device 
>>> 0x10c9
>>> 
>>> /sys/bus/pci/devices/0000:03:00.0# cat vf_did
>>> 0x10ca
>>> 
>>> Putting the VF device ID in the PF device file would be a change of
>>> that we expose to userspace.  Something might break.
>> 
>> Oh, sorry, I misunderstood!  I was thinking that you were adding
>> "vf_did" to the VF directory, not the PF directory.
>> 
>> Then I guess my only issue is that "vf_did" doesn't match the pattern
>> of other names.  I think "virtfn_device" would give more of a hint and
>> would match "device" and "subsystem_device".
> 
> I was going to just make this tweak myself, but realized I'd actually
> propose these changes as well:
> 
>  offset -> sriov_offset
>  stride -> sriov_stride
>  vf_did -> virtfn_device (could be sriov_device as well)
> 
> and I can't really test it to make sure I get all the details right.
> Can you update those and repost this?
> 
> Bjorn

I'll give this a spin tomorrow.

Thanks,
Filippo


>>> vf_did provides a easy way to retrieve the VF device ID without reading
>>> the PF config (looking up the SR-IOV capability and reading it) or without
>>> enabling SR-IOV to read for example virtfn0/device.
>>> 
>>> Similar considerations (ease of access) apply to offset and stride.
>>> 
>>> 
>>>>> static ssize_t sriov_drivers_autoprobe_show(struct device *dev,
>>>>> 					    struct device_attribute *attr,
>>>>> 					    char *buf)
>>>>> @@ -676,6 +703,9 @@ static struct device_attribute sriov_totalvfs_attr = __ATTR_RO(sriov_totalvfs);
>>>>> static struct device_attribute sriov_numvfs_attr =
>>>>> 		__ATTR(sriov_numvfs, (S_IRUGO|S_IWUSR|S_IWGRP),
>>>>> 		       sriov_numvfs_show, sriov_numvfs_store);
>>>>> +static struct device_attribute sriov_offset_attr = __ATTR_RO(sriov_offset);
>>>>> +static struct device_attribute sriov_stride_attr = __ATTR_RO(sriov_stride);
>>>>> +static struct device_attribute sriov_vf_did_attr = __ATTR_RO(sriov_vf_did);
>>>>> static struct device_attribute sriov_drivers_autoprobe_attr =
>>>>> 		__ATTR(sriov_drivers_autoprobe, (S_IRUGO|S_IWUSR|S_IWGRP),
>>>>> 		       sriov_drivers_autoprobe_show, sriov_drivers_autoprobe_store);
>>>>> @@ -1744,6 +1774,9 @@ static struct attribute_group pci_dev_hp_attr_group = {
>>>>> static struct attribute *sriov_dev_attrs[] = {
>>>>> 	&sriov_totalvfs_attr.attr,
>>>>> 	&sriov_numvfs_attr.attr,
>>>>> +	&sriov_offset_attr.attr,
>>>>> +	&sriov_stride_attr.attr,
>>>>> +	&sriov_vf_did_attr.attr,
>>>>> 	&sriov_drivers_autoprobe_attr.attr,
>>>>> 	NULL,
>>>>> };
>>>>> -- 
>>>>> 2.7.4
>>>>> 
>>>> 
>>> 
>>> Amazon Development Center Germany GmbH
>>> Berlin - Dresden - Aachen
>>> main office: Krausenstr. 38, 10117 Berlin
>>> Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger
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Amazon Development Center Germany GmbH
Berlin - Dresden - Aachen
main office: Krausenstr. 38, 10117 Berlin
Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger
Ust-ID: DE289237879
Eingetragen am Amtsgericht Charlottenburg HRB 149173 B