Re: [PATCH] PCI: Reset IOV state on FLR to PF

[Lukasz Maniak <lukasz.maniak@linux.intel.com>]

On Wed, Jan 19, 2022 at 06:22:07PM +0800, Yicong Yang wrote:
> Hi Lukasz, Bjorn,
> 
> FYI, I tested with Mellanox CX-5, the VF also exists after FLR. Here's the operation:

Did you test with or without my patch?

Here is the result with my patch for the NVMe device in QEMU:

root@qemu-sriov:/sys/devices/pci0000:00/0000:00:03.0/0000:01:00.0# lspci -s 01:
01:00.0 Non-Volatile memory controller: Red Hat, Inc. Device 0010 (rev 02)
root@qemu-sriov:/sys/devices/pci0000:00/0000:00:03.0/0000:01:00.0# lspci -vvv -s 01:00.0 | egrep "IOV|VF"
        Capabilities: [120 v1] Single Root I/O Virtualization (SR-IOV)
                IOVCap: Migration-, Interrupt Message Number: 000
                IOVCtl: Enable- Migration- Interrupt- MSE- ARIHierarchy+
                IOVSta: Migration-
                Initial VFs: 8, Total VFs: 8, Number of VFs: 0, Function Dependency Link: 00
                VF offset: 1, stride: 1, Device ID: 0010
                VF Migration: offset: 00000000, BIR: 0
root@qemu-sriov:/sys/devices/pci0000:00/0000:00:03.0/0000:01:00.0# echo 1 > sriov_numvfs
root@qemu-sriov:/sys/devices/pci0000:00/0000:00:03.0/0000:01:00.0# lspci -vvv -s 01:00.0 | egrep "IOV|VF"
        Capabilities: [120 v1] Single Root I/O Virtualization (SR-IOV)
                IOVCap: Migration-, Interrupt Message Number: 000
                IOVCtl: Enable+ Migration- Interrupt- MSE+ ARIHierarchy+
                IOVSta: Migration-
                Initial VFs: 8, Total VFs: 8, Number of VFs: 1, Function Dependency Link: 00
                VF offset: 1, stride: 1, Device ID: 0010
                VF Migration: offset: 00000000, BIR: 0
root@qemu-sriov:/sys/devices/pci0000:00/0000:00:03.0/0000:01:00.0# echo 1 > reset
root@qemu-sriov:/sys/devices/pci0000:00/0000:00:03.0/0000:01:00.0# lspci -vvv -s 01:00.0 | egrep "IOV|VF"
        Capabilities: [120 v1] Single Root I/O Virtualization (SR-IOV)
                IOVCap: Migration-, Interrupt Message Number: 000
                IOVCtl: Enable+ Migration- Interrupt- MSE+ ARIHierarchy+
                IOVSta: Migration-
                Initial VFs: 8, Total VFs: 8, Number of VFs: 0, Function Dependency Link: 00
                VF offset: 1, stride: 1, Device ID: 0010
                VF Migration: offset: 00000000, BIR: 0
root@qemu-sriov:/sys/devices/pci0000:00/0000:00:03.0/0000:01:00.0# lspci -xxx -s 01:00.0
01:00.0 Non-Volatile memory controller: Red Hat, Inc. Device 0010 (rev 02)
00: 36 1b 10 00 07 05 10 00 02 02 08 01 00 00 00 00
10: 04 00 80 fe 00 00 00 00 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 f4 1a 00 11
30: 00 00 00 00 40 00 00 00 00 00 00 00 0b 01 00 00
40: 11 80 40 80 00 20 00 00 00 30 00 00 00 00 00 00
50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
60: 01 00 03 00 08 00 00 00 00 00 00 00 00 00 00 00
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
80: 10 60 02 00 00 80 00 10 00 00 00 00 11 04 00 00
90: 00 00 11 00 00 00 00 00 00 00 00 00 00 00 00 00
a0: 00 00 00 00 00 00 30 00 00 00 00 00 00 00 00 00
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

root@qemu-sriov:/sys/devices/pci0000:00/0000:00:03.0/0000:01:00.0# cat reset_method
flr bus

> 
> [root@localhost ~]# lspci  -s 01:
> 01:00.0 Ethernet controller: Mellanox Technologies MT28800 Family [ConnectX-5 Ex]
> 01:00.1 Ethernet controller: Mellanox Technologies MT28800 Family [ConnectX-5 Ex]
> [root@localhost ~]# lspci -vvv -s 01:00.0 | egrep "IOV|VF"
>         Capabilities: [180 v1] Single Root I/O Virtualization (SR-IOV)
>                 IOVCap: Migration- 10BitTagReq- Interrupt Message Number: 000
>                 IOVCtl: Enable- Migration- Interrupt- MSE- ARIHierarchy+ 10BitTagReq-
>                 IOVSta: Migration-
>                 Initial VFs: 16, Total VFs: 16, Number of VFs: 0, Function Dependency Link: 00
>                 VF offset: 2, stride: 1, Device ID: 101a
>                 VF Migration: offset: 00000000, BIR: 0
> [root@localhost 0000:01:00.0]# echo 1 > sriov_numvfs
> [root@localhost ~]# lspci -vvv -s 01:00.0 | egrep "IOV|VF"
>         Capabilities: [180 v1] Single Root I/O Virtualization (SR-IOV)
>                 IOVCap: Migration- 10BitTagReq- Interrupt Message Number: 000
>                 IOVCtl: Enable+ Migration- Interrupt- MSE+ ARIHierarchy+ 10BitTagReq-
>                 IOVSta: Migration-
>                 Initial VFs: 16, Total VFs: 16, Number of VFs: 1, Function Dependency Link: 00
>                 VF offset: 2, stride: 1, Device ID: 101a
>                 VF Migration: offset: 00000000, BIR: 0
> [root@localhost 0000:01:00.0]# echo 1 > reset
> [root@localhost ~]# lspci -vvv -s 01:00.0 | egrep "IOV|VF"
>         Capabilities: [180 v1] Single Root I/O Virtualization (SR-IOV)
>                 IOVCap: Migration- 10BitTagReq- Interrupt Message Number: 000
>                 IOVCtl: Enable+ Migration- Interrupt- MSE+ ARIHierarchy+ 10BitTagReq-
>                 IOVSta: Migration-
>                 Initial VFs: 16, Total VFs: 16, Number of VFs: 1, Function Dependency Link: 00
>                 VF offset: 2, stride: 1, Device ID: 101a
>                 VF Migration: offset: 00000000, BIR: 0
> [root@localhost ~]# lspci -xxx -s 01:00.0
> 01:00.0 Ethernet controller: Mellanox Technologies MT28800 Family [ConnectX-5 Ex]
> 00: b3 15 19 10 46 05 10 00 00 00 00 02 08 00 80 00
> 10: 0c 00 00 00 00 08 00 00 00 00 00 00 00 00 00 00
> 20: 00 00 00 00 00 00 00 00 00 00 00 00 b3 15 08 00
> 30: 00 00 70 e6 60 00 00 00 00 00 00 00 ff 01 00 00
> 40: 01 00 c3 81 08 00 00 00 03 9c cc 80 00 78 00 00
> 50: 00 00 00 00 00 00 00 00 00 00 00 00 00 20 00 01
> 60: 10 48 02 00 e2 8f e0 11 5f 29 00 00 04 71 41 00
> 70: 08 00 04 11 00 00 00 00 00 00 00 00 00 00 00 00
> 80: 00 00 00 00 17 00 01 00 40 00 00 00 1e 00 80 01
> 90: 04 00 1e 00 00 00 00 00 00 00 00 00 11 c0 3f 80
> a0: 00 20 00 00 00 30 00 00 00 00 00 00 00 00 00 00
> b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> c0: 09 40 18 00 0a 00 00 20 f0 1a 00 00 00 00 00 00
> d0: 20 00 00 80 00 00 00 00 00 00 00 00 00 00 00 00
> e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [root@localhost 0000:01:00.0]# cat reset_method
> flr bus
> 
> On 2022/1/19 10:47, Yicong Yang wrote:
> > On 2022/1/19 0:30, Lukasz Maniak wrote:
> >> On Tue, Jan 18, 2022 at 07:07:23PM +0800, Yicong Yang wrote:
> >>> On 2022/1/18 6:55, Bjorn Helgaas wrote:
> >>>> [+cc Alex in case he has comments on how FLR should work on
> >>>> non-conforming hns3 devices]
> >>>>
> >>>> On Sat, Jan 15, 2022 at 05:22:19PM +0800, Yicong Yang wrote:
> >>>>> On 2022/1/15 0:37, Bjorn Helgaas wrote:
> >>>>>> On Fri, Jan 14, 2022 at 05:42:48PM +0800, Yicong Yang wrote:
> >>>>>>> On 2022/1/14 0:45, Lukasz Maniak wrote:
> >>>>>>>> On Wed, Jan 12, 2022 at 08:49:03AM -0600, Bjorn Helgaas wrote:
> >>>>>>>>> On Wed, Dec 22, 2021 at 08:19:57PM +0100, Lukasz Maniak wrote:
> >>>>>>>>>> As per PCI Express specification, FLR to a PF resets the PF state as
> >>>>>>>>>> well as the SR-IOV extended capability including VF Enable which means
> >>>>>>>>>> that VFs no longer exist.
> >>>>>>>>>
> >>>>>>>>> Can you add a specific reference to the spec, please?
> >>>>>>>>>
> >>>>>>>> Following the Single Root I/O Virtualization and Sharing Specification:
> >>>>>>>> 2.2.3. FLR That Targets a PF
> >>>>>>>> PFs must support FLR.
> >>>>>>>> FLR to a PF resets the PF state as well as the SR-IOV extended
> >>>>>>>> capability including VF Enable which means that VFs no longer exist.
> >>>>>>>>
> >>>>>>>> For PCI Express Base Specification Revision 5.0 and later, this is
> >>>>>>>> section 9.2.2.3.
> >>>>>>
> >>>>>> This is also the section in the new PCIe r6.0.  Let's use that.
> >>>>>>
> >>>>>>>>>> Currently, the IOV state is not updated during FLR, resulting in
> >>>>>>>>>> non-compliant PCI driver behavior.
> >>>>>>>>>
> >>>>>>>>> And include a little detail about what problem is observed?  How would
> >>>>>>>>> a user know this problem is occurring?
> >>>>>>>>>
> >>>>>>>> The problem is that the state of the kernel and HW as to the number of
> >>>>>>>> VFs gets out of sync after FLR.
> >>>>>>>>
> >>>>>>>> This results in further listing, after the FLR is performed by the HW,
> >>>>>>>> of VFs that actually no longer exist and should no longer be reported on
> >>>>>>>> the PCI bus. lspci return FFs for these VFs.
> >>>>>>>
> >>>>>>> There're some exceptions. Take HiSilicon's hns3 and sec device as an
> >>>>>>> example, the VF won't be destroyed after the FLR reset.
> >>>>>>
> >>>>>> If FLR on an hns3 PF does *not* clear VF Enable, and the VFs still
> >>>>>> exist after FLR, isn't that a violation of sec 9.2.2.3?
> >>>>>
> >>>>> yes I think it's a violation to the spec.
> >>>>
> >>>> Thanks for confirming that.
> >>>>
> >>>>>> If hns3 and sec don't conform to the spec, we should have some sort of
> >>>>>> quirk that serves to document and work around this.
> >>>>>
> >>>>> ok I think it'll help. Do you mean something like this based on this patch:
> >>>>>
> >>>>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> >>>>> index 69ee321027b4..0e4976c669b2 100644
> >>>>> --- a/drivers/pci/iov.c
> >>>>> +++ b/drivers/pci/iov.c
> >>>>> @@ -1025,6 +1025,8 @@ void pci_reset_iov_state(struct pci_dev *dev)
> >>>>>  		return;
> >>>>>  	if (!iov->num_VFs)
> >>>>>  		return;
> >>>>> +	if (dev->flr_no_vf_reset)
> >>>>> +		return;
> >>>>>
> >>>>>  	sriov_del_vfs(dev);
> >>>>>
> >>>>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> >>>>> index 003950c738d2..c8ffcb0ac612 100644
> >>>>> --- a/drivers/pci/quirks.c
> >>>>> +++ b/drivers/pci/quirks.c
> >>>>> @@ -1860,6 +1860,17 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa256, quirk_huawei_pcie_sva);
> >>>>>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa258, quirk_huawei_pcie_sva);
> >>>>>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa259, quirk_huawei_pcie_sva);
> >>>>>
> >>>>> +/*
> >>>>> + * Some HiSilicon PCIe devices' VF won't be destroyed after a FLR reset.
> >>>>> + * Don't reset these devices' IOV state when doing FLR.
> >>>>> + */
> >>>>> +static void quirk_huawei_pcie_flr(struct pci_dev *pdev)
> >>>>> +{
> >>>>> +	pdev->flr_no_vf_reset = 1;
> >>>>> +}
> >>>>> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa255, quirk_huawei_pcie_flr);
> >>>>> +/* ...some other devices have this quirk */
> >>>>
> >>>> Yes, I think something along this line will help.
> >>>>
> >>>>> diff --git a/include/linux/pci.h b/include/linux/pci.h
> >>>>> index 18a75c8e615c..e62f9fa4d48f 100644
> >>>>> --- a/include/linux/pci.h
> >>>>> +++ b/include/linux/pci.h
> >>>>> @@ -454,6 +454,7 @@ struct pci_dev {
> >>>>>  	unsigned int	is_probed:1;		/* Device probing in progress */
> >>>>>  	unsigned int	link_active_reporting:1;/* Device capable of reporting link active */
> >>>>>  	unsigned int	no_vf_scan:1;		/* Don't scan for VFs after IOV enablement */
> >>>>> +	unsigned int	flr_no_vf_reset:1;	/* VF won't be destroyed after PF's FLR */
> >>>>>
> >>>>>>> Currently the transactions with the VF will be restored after the
> >>>>>>> FLR. But this patch will break that, the VF is fully disabled and
> >>>>>>> the transaction cannot be restored. User needs to reconfigure it,
> >>>>>>> which is unnecessary before this patch.
> >>>>>>
> >>>>>> What does it mean for a "transaction to be restored"?  Maybe you mean
> >>>>>> this patch removes the *VFs* via sriov_del_vfs(), and whoever
> >>>>>> initiated the FLR would need to re-enable VFs via pci_enable_sriov()
> >>>>>> or something similar?
> >>>>>
> >>>>> Partly. It'll also terminate the VF users.
> >>>>> Think that I attach the VF of hns to a VM by vfio and ping the network
> >>>>> in the VM, when doing FLR the 'ping' will pause and after FLR it'll
> >>>>> resume. Currenlty The driver handle this in the ->reset_{prepare, done}()
> >>>>> methods. The user of VM may not realize there is a FLR of the PF as the
> >>>>> VF always exists and the 'ping' is never terminated.
> >>>>>
> >>>>> If we remove the VF when doing FLR, then 1) we'll block in the VF->remove()
> >>>>> until no one is using the device, for example the 'ping' is finished.
> >>>>> 2) the VF in the VM no longer exists and we have to re-enable VF and hotplug
> >>>>> it into the VM and restart the ping. That's a big difference.
> >>>>>
> >>>>>> If FLR disables VFs, it seems like we should expect to have to
> >>>>>> re-enable them if we want them.
> >>>>>
> >>>>> It involves a remove()/probe() process of the VF driver and the user
> >>>>> of the VF will be terminated, just like the situation illustrated
> >>>>> above.
> >>>>
> >>>> I think users of FLR should be able to rely on it working per spec,
> >>>> i.e., that VFs will be destroyed.  If hardware like hns3 doesn't do
> >>>> that, the quirk should work around that in software by doing it
> >>>> explicitly.
> >>>>
> >>>> I don't think the non-standard behavior should be exposed to the
> >>>> users.  The user should not have to know about this hns3 issue.
> >>>>
> >>>> If FLR on a standard NIC terminates a ping on a VF, FLR on an hns3 NIC
> >>>> should also terminate a ping on a VF.
> >>>>
> >>>
> >>> ok thanks for the discussion, agree on that. According to the spec, after
> >>> the FLR to the PF the VF does not exist anymore, so the ping will be terminated.
> >>> Our hns3 and sec team are still evaluating it before coming to a solution of
> >>> whether using a quirk or comform to the spec.
> >>>
> >>> For this patch it looks reasonable to me, but some questions about the code below.
> >>>
> >>>>>>> Can we handle this problem in another way? Maybe test the VF's
> >>>>>>> vendor device ID after the FLR reset to see whether it has really
> >>>>>>> gone or not?
> >>>>>>>
> >>>>>>>> sriov_numvfs in sysfs returns old invalid value and does not allow
> >>>>>>>> setting a new value before explicitly setting 0 in the first place.
> >>>>>>>>
> >>>>>>>>>> This patch introduces a simple function, called on the FLR path, that
> >>>>>>>>>> removes the virtual function devices from the PCI bus and their
> >>>>>>>>>> corresponding sysfs links with a final clear of the num_vfs value in IOV
> >>>>>>>>>> state.
> >>>>>>>>>>
> >>>>>>>>>> Signed-off-by: Lukasz Maniak <lukasz.maniak@linux.intel.com>
> >>>>>>>>>> ---
> >>>>>>>>>>  drivers/pci/iov.c | 21 +++++++++++++++++++++
> >>>>>>>>>>  drivers/pci/pci.c |  2 ++
> >>>>>>>>>>  drivers/pci/pci.h |  4 ++++
> >>>>>>>>>>  3 files changed, 27 insertions(+)
> >>>>>>>>>>
> >>>>>>>>>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> >>>>>>>>>> index 0267977c9f17..69ee321027b4 100644
> >>>>>>>>>> --- a/drivers/pci/iov.c
> >>>>>>>>>> +++ b/drivers/pci/iov.c
> >>>>>>>>>> @@ -1013,6 +1013,27 @@ int pci_iov_bus_range(struct pci_bus *bus)
> >>>>>>>>>>  	return max ? max - bus->number : 0;
> >>>>>>>>>>  }
> >>>>>>>>>>  
> >>>>>>>>>> +/**
> >>>>>>>>>> + * pci_reset_iov_state - reset the state of the IOV capability
> >>>>>>>>>> + * @dev: the PCI device
> >>>>>>>>>> + */
> >>>>>>>>>> +void pci_reset_iov_state(struct pci_dev *dev)
> >>>>>>>>>> +{
> >>>>>>>>>> +	struct pci_sriov *iov = dev->sriov;
> >>>>>>>>>> +
> >>>>>>>>>> +	if (!dev->is_physfn)
> >>>>>>>>>> +		return;
> >>>>>>>>>> +	if (!iov->num_VFs)
> >>>>>>>>>> +		return;
> >>>>>>>>>> +
> >>>>>>>>>> +	sriov_del_vfs(dev);
> >>>>>>>>>> +
> >>>>>>>>>> +	if (iov->link != dev->devfn)
> >>>>>>>>>> +		sysfs_remove_link(&dev->dev.kobj, "dep_link");
> >>>>>>>>>> +
> >>>>>>>>>> +	iov->num_VFs = 0;
> >>>>>>>>>> +}
> >>>>>>>>>> +
> >>>
> >>> Any reason for not using pci_disable_sriov()?
> >>
> >> The issue with pci_disable_sriov() is that it calls sriov_disable(),
> >> which directly uses pci_cfg_access_lock(), leading to deadlock on the
> >> FLR path.
> >>
> > 
> > That'll be a problem. Well my main concern is whether the VFs will be reset
> > correctly through pci_reset_iov_state() as it lacks the participant of
> > PF driver and bios (seems may needed only on powerpc, not sure), which is
> > necessary in the enable/disable routine through $pci_dev/sriov_numvfs.
> > 
> >>>
> >>> With the spec the related registers in the SRIOV cap will be reset so
> >>> it's ok in general. But for some devices not following the spec like hns3,
> >>> some fields like VF enable won't be reset and keep enabled after the FLR.
> >>> In this case after the FLR the VF devices in the system has gone but
> >>> the state of the PF SRIOV cap leaves uncleared. pci_disable_sriov()
> >>> will reset the whole SRIOV cap. It'll also call pcibios_sriov_disable()
> >>> to correct handle the VF disabling on some platforms, IIUC.
> >>>
> >>> Or is it better to use pdev->driver->sriov_configure(pdev,0)?
> >>> PF drivers must implement ->sriov_configure() for enabling/disabling
> >>> the VF but we totally skip the PF driver here.
> >>>
> >>> Thanks,
> >>> Yicong
> >>>
> >>>>>>>>>>  /**
> >>>>>>>>>>   * pci_enable_sriov - enable the SR-IOV capability
> >>>>>>>>>>   * @dev: the PCI device
> >>>>>>>>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> >>>>>>>>>> index 3d2fb394986a..535f19d37e8d 100644
> >>>>>>>>>> --- a/drivers/pci/pci.c
> >>>>>>>>>> +++ b/drivers/pci/pci.c
> >>>>>>>>>> @@ -4694,6 +4694,8 @@ EXPORT_SYMBOL(pci_wait_for_pending_transaction);
> >>>>>>>>>>   */
> >>>>>>>>>>  int pcie_flr(struct pci_dev *dev)
> >>>>>>>>>>  {
> >>>>>>>>>> +	pci_reset_iov_state(dev);
> >>>>>>>>>> +
> >>>>>>>>>>  	if (!pci_wait_for_pending_transaction(dev))
> >>>>>>>>>>  		pci_err(dev, "timed out waiting for pending transaction; performing function level reset anyway\n");
> >>>>>>>>>>  
> >>>>>>>>>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> >>>>>>>>>> index 3d60cabde1a1..7bb144fbec76 100644
> >>>>>>>>>> --- a/drivers/pci/pci.h
> >>>>>>>>>> +++ b/drivers/pci/pci.h
> >>>>>>>>>> @@ -480,6 +480,7 @@ void pci_iov_update_resource(struct pci_dev *dev, int resno);
> >>>>>>>>>>  resource_size_t pci_sriov_resource_alignment(struct pci_dev *dev, int resno);
> >>>>>>>>>>  void pci_restore_iov_state(struct pci_dev *dev);
> >>>>>>>>>>  int pci_iov_bus_range(struct pci_bus *bus);
> >>>>>>>>>> +void pci_reset_iov_state(struct pci_dev *dev);
> >>>>>>>>>>  extern const struct attribute_group sriov_pf_dev_attr_group;
> >>>>>>>>>>  extern const struct attribute_group sriov_vf_dev_attr_group;
> >>>>>>>>>>  #else
> >>>>>>>>>> @@ -501,6 +502,9 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)
> >>>>>>>>>>  {
> >>>>>>>>>>  	return 0;
> >>>>>>>>>>  }
> >>>>>>>>>> +static inline void pci_reset_iov_state(struct pci_dev *dev)
> >>>>>>>>>> +{
> >>>>>>>>>> +}
> >>>>>>>>>>  
> >>>>>>>>>>  #endif /* CONFIG_PCI_IOV */
> >>>> .
> >>>>
> >> .
> >>
> > .
> >