| Message ID | 1473199219-3369-2-git-send-email-keith.busch@intel.com |
|---|---|
| State | Changes Requested |
| Headers | show |
On Tue, Sep 06, 2016 at 04:00:16PM -0600, Keith Busch wrote: > This adds a new state for devices that were once in the system, but > unexpectedly removed. This is so device teardown functions can observe > the device is not accessible so it may skip attempting to initialize ^ they ^ access (?) > the hardware. > > The pciehp and pcie-dpc drivers are aware of when the link is down, so > they explicitly set this flag when its handlers detect the device is gone. ^ their > > The flag is also cached any time pci_device_is_present returns false. The > function checks the flag first to avoid additional config accesses to > removed devices. > > Signed-off-by: Keith Busch <keith.busch@intel.com> Reviewed-by: Lukas Wunner <lukas@wunner.de> I think this is a significant improvement because with Thunderbolt, devices can disappear at any time and many drivers currently access the device in their ->remove hook, which is fine if the driver detachment is caused by "modprobe -r" but entirely wrong in the case of a surprise removal. This patch adds the necessary infrastructure for drivers to adjust their behaviour during ->remove if the device is gone. Thanks, Lukas > --- > drivers/pci/hotplug/pciehp_pci.c | 2 ++ > drivers/pci/pci.c | 9 ++++++++- > drivers/pci/pcie/pcie-dpc.c | 1 + > include/linux/pci.h | 1 + > 4 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c > index 9e69403..299ea5e 100644 > --- a/drivers/pci/hotplug/pciehp_pci.c > +++ b/drivers/pci/hotplug/pciehp_pci.c > @@ -109,6 +109,8 @@ int pciehp_unconfigure_device(struct slot *p_slot) > break; > } > } > + if (!presence) > + dev->is_removed = 1; > pci_stop_and_remove_bus_device(dev); > /* > * Ensure that no new Requests will be generated from > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index aab9d51..010e5f6 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -4924,7 +4924,14 @@ bool pci_device_is_present(struct pci_dev *pdev) > { > u32 v; > > - return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0); > + if (pdev->is_removed) > + return false; > + > + if (!pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0)) { > + pdev->is_removed = 1; > + return false; > + } > + return true; > } > EXPORT_SYMBOL_GPL(pci_device_is_present); > > diff --git a/drivers/pci/pcie/pcie-dpc.c b/drivers/pci/pcie/pcie-dpc.c > index 9811b14..2e5876c5 100644 > --- a/drivers/pci/pcie/pcie-dpc.c > +++ b/drivers/pci/pcie/pcie-dpc.c > @@ -46,6 +46,7 @@ static void interrupt_event_handler(struct work_struct *work) > list_for_each_entry_safe_reverse(dev, temp, &parent->devices, > bus_list) { > pci_dev_get(dev); > + dev->is_removed = 1; > pci_stop_and_remove_bus_device(dev); > pci_dev_put(dev); > } > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 7256f33..865d3ec 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -334,6 +334,7 @@ struct pci_dev { > unsigned int multifunction:1;/* Part of multi-function device */ > /* keep track of device state */ > unsigned int is_added:1; > + unsigned int is_removed:1; /* device was surprise removed */ > unsigned int is_busmaster:1; /* device is busmaster */ > unsigned int no_msi:1; /* device may not use msi */ > unsigned int no_64bit_msi:1; /* device may only use 32-bit MSIs */ > -- > 2.7.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Sep 06, 2016 at 04:00:16PM -0600, Keith Busch wrote: > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -4924,7 +4924,14 @@ bool pci_device_is_present(struct pci_dev *pdev) > { > u32 v; > > - return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0); > + if (pdev->is_removed) > + return false; > + > + if (!pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0)) { > + pdev->is_removed = 1; > + return false; > + } > + return true; > } > EXPORT_SYMBOL_GPL(pci_device_is_present); I've kept this series on my development branch and found a bug now: In the above hunk, it's okay to return false if pdev->is_removed is set, but it's not okay to set pdev->is_removed if pci_bus_read_dev_vendor_id() returns false. That's because pci_bus_read_dev_vendor_id() can fail for other reasons, such as the device being powered down to D3cold, or currently unreachable because a PCIe port above it was suspended to D3hot so that the link is down. Those are transient issues, the device isn't removed in those cases. IOW the hunk should look like this: { u32 v; + if (pdev->is_removed) + return false; + return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0); } And this should then probably be moved to patch [2/4]. Best regards, Lukas -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Sep 17, 2016 at 10:35:06AM +0200, Lukas Wunner wrote: > On Tue, Sep 06, 2016 at 04:00:16PM -0600, Keith Busch wrote: > > - return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0); > > + if (pdev->is_removed) > > + return false; > > + > > + if (!pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0)) { > > + pdev->is_removed = 1; > > + return false; > > + } > > + return true; > > } > > EXPORT_SYMBOL_GPL(pci_device_is_present); > > I've kept this series on my development branch and found a bug now: > > In the above hunk, it's okay to return false if pdev->is_removed is set, > but it's not okay to set pdev->is_removed if pci_bus_read_dev_vendor_id() > returns false. That's because pci_bus_read_dev_vendor_id() can fail for > other reasons, such as the device being powered down to D3cold, or > currently unreachable because a PCIe port above it was suspended to D3hot > so that the link is down. Those are transient issues, the device isn't > removed in those cases. Thanks for the info. I wasn't sure about making the removed return sticky on a failed vendor id check, so I will remove that from this path and resend the entire series. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c index 9e69403..299ea5e 100644 --- a/drivers/pci/hotplug/pciehp_pci.c +++ b/drivers/pci/hotplug/pciehp_pci.c @@ -109,6 +109,8 @@ int pciehp_unconfigure_device(struct slot *p_slot) break; } } + if (!presence) + dev->is_removed = 1; pci_stop_and_remove_bus_device(dev); /* * Ensure that no new Requests will be generated from diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index aab9d51..010e5f6 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4924,7 +4924,14 @@ bool pci_device_is_present(struct pci_dev *pdev) { u32 v; - return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0); + if (pdev->is_removed) + return false; + + if (!pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0)) { + pdev->is_removed = 1; + return false; + } + return true; } EXPORT_SYMBOL_GPL(pci_device_is_present); diff --git a/drivers/pci/pcie/pcie-dpc.c b/drivers/pci/pcie/pcie-dpc.c index 9811b14..2e5876c5 100644 --- a/drivers/pci/pcie/pcie-dpc.c +++ b/drivers/pci/pcie/pcie-dpc.c @@ -46,6 +46,7 @@ static void interrupt_event_handler(struct work_struct *work) list_for_each_entry_safe_reverse(dev, temp, &parent->devices, bus_list) { pci_dev_get(dev); + dev->is_removed = 1; pci_stop_and_remove_bus_device(dev); pci_dev_put(dev); } diff --git a/include/linux/pci.h b/include/linux/pci.h index 7256f33..865d3ec 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -334,6 +334,7 @@ struct pci_dev { unsigned int multifunction:1;/* Part of multi-function device */ /* keep track of device state */ unsigned int is_added:1; + unsigned int is_removed:1; /* device was surprise removed */ unsigned int is_busmaster:1; /* device is busmaster */ unsigned int no_msi:1; /* device may not use msi */ unsigned int no_64bit_msi:1; /* device may only use 32-bit MSIs */
This adds a new state for devices that were once in the system, but unexpectedly removed. This is so device teardown functions can observe the device is not accessible so it may skip attempting to initialize the hardware. The pciehp and pcie-dpc drivers are aware of when the link is down, so they explicitly set this flag when its handlers detect the device is gone. The flag is also cached any time pci_device_is_present returns false. The function checks the flag first to avoid additional config accesses to removed devices. Signed-off-by: Keith Busch <keith.busch@intel.com> --- drivers/pci/hotplug/pciehp_pci.c | 2 ++ drivers/pci/pci.c | 9 ++++++++- drivers/pci/pcie/pcie-dpc.c | 1 + include/linux/pci.h | 1 + 4 files changed, 12 insertions(+), 1 deletion(-)