[+cc Ashok, Alex, Sinan, Rajat]
On Sun, Feb 23, 2020 at 01:20:56PM +0100, Stanislav Spassov wrote:
> From: Stanislav Spassov <stanspas@xxxxxxxxx>
>
> A broken device may never become responsive after reset, hence the need
> for a timeout. However, waiting for too long can have unintended side
> effects such as triggering hung task timeouts for processes waiting on
> a lock held during the reset. Locks that are shared across multiple
> devices, such as VFIO's per-bus reflck, are especially problematic,
> because a single broken VF can cause hangs for processes working with
> other VFs on the same bus.
>
> To allow lowering the global default post-reset timeout, while still
> accommodating devices that require more time, this patch introduces
> a per-device override that can be configured via a quirk.
>
> Signed-off-by: Stanislav Spassov <stanspas@xxxxxxxxx>
> ---
> drivers/pci/pci.c | 19 ++++++++++++++-----
> drivers/pci/probe.c | 2 ++
> include/linux/pci.h | 1 +
> 3 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index db9b58ab6c68..a554818968ed 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1033,8 +1033,17 @@ void pci_wakeup_bus(struct pci_bus *bus)
> pci_walk_bus(bus, pci_wakeup, NULL);
> }
>
> -static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
> +static int pci_dev_get_reset_ready_poll_ms(struct pci_dev *dev)
> {
> + if (dev->reset_ready_poll_ms >= 0)
> + return dev->reset_ready_poll_ms;
> +
> + return pcie_reset_ready_poll_ms;
> +}
> +
> +static int pci_dev_wait(struct pci_dev *dev, char *reset_type)
> +{
> + int timeout = pci_dev_get_reset_ready_poll_ms(dev);
I like the factoring out of the timeout, since all callers of
pci_dev_wait() supply the same value. That could be its own separate
preliminary patch, e.g., simply
-static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
+static int pci_dev_wait(struct pci_dev *dev, char *reset_type)
{
+ int timeout = PCIE_RESET_READY_POLL_MS;
...
- return pci_dev_wait(dev, "FLR", PCIE_RESET_READY_POLL_MS);
+ return pci_dev_wait(dev, "FLR");
I'm a little wary of "lowering the global default post-reset timeout"
because that's not safe in general. For example, a hot-added device
that is completely spec compliant regarding post-reset timing may not
work correctly if we've lowered a global timeout.
> int delay = 1;
> u32 id;
>
> @@ -4518,7 +4527,7 @@ int pcie_flr(struct pci_dev *dev)
> */
> msleep(100);
>
> - return pci_dev_wait(dev, "FLR", pcie_reset_ready_poll_ms);
> + return pci_dev_wait(dev, "FLR");
> }
> EXPORT_SYMBOL_GPL(pcie_flr);
>
> @@ -4563,7 +4572,7 @@ static int pci_af_flr(struct pci_dev *dev, int probe)
> */
> msleep(100);
>
> - return pci_dev_wait(dev, "AF_FLR", pcie_reset_ready_poll_ms);
> + return pci_dev_wait(dev, "AF_FLR");
> }
>
> /**
> @@ -4608,7 +4617,7 @@ static int pci_pm_reset(struct pci_dev *dev, int probe)
> pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, csr);
> pci_dev_d3_sleep(dev);
>
> - return pci_dev_wait(dev, "PM D3hot->D0", pcie_reset_ready_poll_ms);
> + return pci_dev_wait(dev, "PM D3hot->D0");
> }
>
> /**
> @@ -4838,7 +4847,7 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev)
> {
> pcibios_reset_secondary_bus(dev);
>
> - return pci_dev_wait(dev, "bus reset", pcie_reset_ready_poll_ms);
> + return pci_dev_wait(dev, "bus reset");
> }
> EXPORT_SYMBOL_GPL(pci_bridge_secondary_bus_reset);
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 512cb4312ddd..eeb79a45d504 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2166,6 +2166,8 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
> if (!dev)
> return NULL;
>
> + dev->reset_ready_poll_ms = -1;
> +
> INIT_LIST_HEAD(&dev->bus_list);
> dev->dev.type = &pci_dev_type;
> dev->bus = pci_bus_get(bus);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 3840a541a9de..049a41b9412b 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -468,6 +468,7 @@ struct pci_dev {
> size_t romlen; /* Length if not from BAR */
> char *driver_override; /* Driver name to force a match */
>
> + int reset_ready_poll_ms;
> unsigned long priv_flags; /* Private flags for the PCI driver */
> };
