If a device is in an error state, then any reads of device registers can
return error value. Add addtional checks to validate if a device is in an
error state before doing an flr reset.
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
drivers/pci/pci.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index a3d93d1baee7..327fefc6a1eb 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4576,12 +4576,19 @@ EXPORT_SYMBOL_GPL(pcie_flr);
*/
int pcie_reset_flr(struct pci_dev *dev, bool probe)
{
+ u32 reg;
+
if (dev->dev_flags & PCI_DEV_FLAGS_NO_FLR_RESET)
return -ENOTTY;
if (!(dev->devcap & PCI_EXP_DEVCAP_FLR))
return -ENOTTY;
+ if (pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, ®)) {
+ pci_warn(dev, "Device unable to do an FLR\n");
+ return -ENOTTY;
+ }
+
if (probe)
return 0;
--
2.43.0On Wed, Sep 24, 2025 at 10:16:20AM -0700, Farhan Ali wrote: > If a device is in an error state, then any reads of device registers can > return error value. Add addtional checks to validate if a device is in an > error state before doing an flr reset. > > Signed-off-by: Farhan Ali <alifm@linux.ibm.com> > --- > drivers/pci/pci.c | 7 +++++++ > 1 file changed, 7 insertions(+) > Apart from the discussion about a stable tag this looks good to me. Reviewed-by: Benjamin Block <bblock@linux.ibm.com> -- Best Regards, Benjamin Block / Linux on IBM Z Kernel Development IBM Deutschland Research & Development GmbH / https://www.ibm.com/privacy Vors. Aufs.-R.: Wolfgang Wendt / Geschäftsführung: David Faller Sitz der Ges.: Böblingen / Registergericht: AmtsG Stuttgart, HRB 243294
On Wed, Sep 24, 2025 at 10:16:20AM -0700, Farhan Ali wrote:
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index a3d93d1baee7..327fefc6a1eb 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4576,12 +4576,19 @@ EXPORT_SYMBOL_GPL(pcie_flr);
> */
> int pcie_reset_flr(struct pci_dev *dev, bool probe)
> {
> + u32 reg;
> +
> if (dev->dev_flags & PCI_DEV_FLAGS_NO_FLR_RESET)
> return -ENOTTY;
>
> if (!(dev->devcap & PCI_EXP_DEVCAP_FLR))
> return -ENOTTY;
>
> + if (pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, ®)) {
> + pci_warn(dev, "Device unable to do an FLR\n");
> + return -ENOTTY;
> + }
Just thinking out loud, not sure whether it make sense, but since you already
read an up-to-date value from the config space, would it make sense to
pull the check above `dev->devcap & PCI_EXP_DEVCAP_FLR` below this read, and
check on the just read `reg`?
Also wondering whether it makes sense to stable-tag this? We've recently seen
"unpleasant" recovery attempts that look like this in the kernel logs:
[ 663.330053] vfio-pci 0007:00:00.1: timed out waiting for pending transaction; performing function level reset anyway
[ 664.730051] vfio-pci 0007:00:00.1: not ready 1023ms after FLR; waiting
[ 665.830023] vfio-pci 0007:00:00.1: not ready 2047ms after FLR; waiting
[ 667.910023] vfio-pci 0007:00:00.1: not ready 4095ms after FLR; waiting
[ 672.070022] vfio-pci 0007:00:00.1: not ready 8191ms after FLR; waiting
[ 680.550025] vfio-pci 0007:00:00.1: not ready 16383ms after FLR; waiting
[ 697.190023] vfio-pci 0007:00:00.1: not ready 32767ms after FLR; waiting
[ 730.470021] vfio-pci 0007:00:00.1: not ready 65535ms after FLR; giving up
The VF here was already dead in the water at that point, so I suspect
`pci_read_config_dword()` might have failed, and so this check would have
failed, and we wouldn't have "wasted" the minute waiting for a FLR that was
never going to happen anyway.
--
Best Regards, Benjamin Block / Linux on IBM Z Kernel Development
IBM Deutschland Research & Development GmbH / https://www.ibm.com/privacy
Vors. Aufs.-R.: Wolfgang Wendt / Geschäftsführung: David Faller
Sitz der Ges.: Böblingen / Registergericht: AmtsG Stuttgart, HRB 243294
On 9/30/2025 3:03 AM, Benjamin Block wrote:
> On Wed, Sep 24, 2025 at 10:16:20AM -0700, Farhan Ali wrote:
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index a3d93d1baee7..327fefc6a1eb 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -4576,12 +4576,19 @@ EXPORT_SYMBOL_GPL(pcie_flr);
>> */
>> int pcie_reset_flr(struct pci_dev *dev, bool probe)
>> {
>> + u32 reg;
>> +
>> if (dev->dev_flags & PCI_DEV_FLAGS_NO_FLR_RESET)
>> return -ENOTTY;
>>
>> if (!(dev->devcap & PCI_EXP_DEVCAP_FLR))
>> return -ENOTTY;
>>
>> + if (pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, ®)) {
>> + pci_warn(dev, "Device unable to do an FLR\n");
>> + return -ENOTTY;
>> + }
> Just thinking out loud, not sure whether it make sense, but since you already
> read an up-to-date value from the config space, would it make sense to
> pull the check above `dev->devcap & PCI_EXP_DEVCAP_FLR` below this read, and
> check on the just read `reg`?
My thinking was we could exit early if the device never had FLR
capability (and so was not cached in devcap). This way we avoid an extra
PCI read.
>
> Also wondering whether it makes sense to stable-tag this? We've recently seen
> "unpleasant" recovery attempts that look like this in the kernel logs:
>
> [ 663.330053] vfio-pci 0007:00:00.1: timed out waiting for pending transaction; performing function level reset anyway
> [ 664.730051] vfio-pci 0007:00:00.1: not ready 1023ms after FLR; waiting
> [ 665.830023] vfio-pci 0007:00:00.1: not ready 2047ms after FLR; waiting
> [ 667.910023] vfio-pci 0007:00:00.1: not ready 4095ms after FLR; waiting
> [ 672.070022] vfio-pci 0007:00:00.1: not ready 8191ms after FLR; waiting
> [ 680.550025] vfio-pci 0007:00:00.1: not ready 16383ms after FLR; waiting
> [ 697.190023] vfio-pci 0007:00:00.1: not ready 32767ms after FLR; waiting
> [ 730.470021] vfio-pci 0007:00:00.1: not ready 65535ms after FLR; giving up
>
> The VF here was already dead in the water at that point, so I suspect
> `pci_read_config_dword()` might have failed, and so this check would have
> failed, and we wouldn't have "wasted" the minute waiting for a FLR that was
> never going to happen anyway.
I think maybe we could? I don't think this patch fixes anything that's
"broken" but rather improves the behavior to escalate to other reset
method if the device is already in a bad state. I will cc stable.
Thanks
Farhan
On Tue, Sep 30, 2025 at 10:04:25AM -0700, Farhan Ali wrote:
>
> On 9/30/2025 3:03 AM, Benjamin Block wrote:
> > On Wed, Sep 24, 2025 at 10:16:20AM -0700, Farhan Ali wrote:
> >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> >> index a3d93d1baee7..327fefc6a1eb 100644
> >> --- a/drivers/pci/pci.c
> >> +++ b/drivers/pci/pci.c
--8<--
> >> + if (pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, ®)) {
> >> + pci_warn(dev, "Device unable to do an FLR\n");
> >> + return -ENOTTY;
> >> + }
> > Just thinking out loud, not sure whether it make sense, but since you already
> > read an up-to-date value from the config space, would it make sense to
> > pull the check above `dev->devcap & PCI_EXP_DEVCAP_FLR` below this read, and
> > check on the just read `reg`?
>
> My thinking was we could exit early if the device never had FLR
> capability (and so was not cached in devcap). This way we avoid an extra
> PCI read.
That makes sense.
> > Also wondering whether it makes sense to stable-tag this? We've recently seen
> > "unpleasant" recovery attempts that look like this in the kernel logs:
> >
> > [ 663.330053] vfio-pci 0007:00:00.1: timed out waiting for pending transaction; performing function level reset anyway
> > [ 664.730051] vfio-pci 0007:00:00.1: not ready 1023ms after FLR; waiting
> > [ 665.830023] vfio-pci 0007:00:00.1: not ready 2047ms after FLR; waiting
> > [ 667.910023] vfio-pci 0007:00:00.1: not ready 4095ms after FLR; waiting
> > [ 672.070022] vfio-pci 0007:00:00.1: not ready 8191ms after FLR; waiting
> > [ 680.550025] vfio-pci 0007:00:00.1: not ready 16383ms after FLR; waiting
> > [ 697.190023] vfio-pci 0007:00:00.1: not ready 32767ms after FLR; waiting
> > [ 730.470021] vfio-pci 0007:00:00.1: not ready 65535ms after FLR; giving up
> >
> > The VF here was already dead in the water at that point, so I suspect
> > `pci_read_config_dword()` might have failed, and so this check would have
> > failed, and we wouldn't have "wasted" the minute waiting for a FLR that was
> > never going to happen anyway.
>
> I think maybe we could? I don't think this patch fixes anything that's
> "broken" but rather improves the behavior to escalate to other reset
> method if the device is already in a bad state. I will cc stable.
Right, adding a Fixes tag doesn't really make sense. But it does help with
accelerating recoveries, so maybe a stable tag will work :)
--
Best Regards, Benjamin Block / Linux on IBM Z Kernel Development
IBM Deutschland Research & Development GmbH / https://www.ibm.com/privacy
Vors. Aufs.-R.: Wolfgang Wendt / Geschäftsführung: David Faller
Sitz der Ges.: Böblingen / Registergericht: AmtsG Stuttgart, HRB 243294
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