[+cc Alex, Amey, Raphael]
On Fri, Oct 25, 2024 at 07:50:21AM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch@xxxxxxxxxx>
>
> Attempting a bus reset on an end device only works if it's the only
> function on or below that bus.
>
> Provide an attribute on the pci_bus device that can perform the
> secondary bus reset. This makes it possible for a user to safely reset
> multiple devices in a single command using the secondary bus reset
> method.
I confess to being a little ambivalent or even hesitant about
operations on the pci_bus (as opposed to on a pci_dev), but I can't
really articulate a great reason, other than the fact that the "bus"
is kind of abstract and from a hardware perspective, the *devices* are
the only things we can control.
I assume this is useful in some scenario. I guess this is root-only,
so there's no real concern about whether all the devices are used by
the same VM or in the same IOMMU group or anything?
> Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>
> ---
> drivers/pci/pci-sysfs.c | 23 +++++++++++++++++++++++
> drivers/pci/pci.c | 2 +-
> drivers/pci/pci.h | 1 +
> 3 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 5d0f4db1cab78..616d64f12da4d 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -521,6 +521,28 @@ static ssize_t bus_rescan_store(struct device *dev,
> static struct device_attribute dev_attr_bus_rescan = __ATTR(rescan, 0200, NULL,
> bus_rescan_store);
>
> +static ssize_t bus_reset_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct pci_bus *bus = to_pci_bus(dev);
> + unsigned long val;
> +
> + if (kstrtoul(buf, 0, &val) < 0)
> + return -EINVAL;
> +
> + if (val) {
> + int ret = __pci_reset_bus(bus);
> +
> + if (ret)
> + return ret;
> + }
> +
> + return count;
> +}
> +static struct device_attribute dev_attr_bus_reset = __ATTR(reset, 0200, NULL,
> + bus_reset_store);
> +
> #if defined(CONFIG_PM) && defined(CONFIG_ACPI)
> static ssize_t d3cold_allowed_store(struct device *dev,
> struct device_attribute *attr,
> @@ -638,6 +660,7 @@ static struct attribute *pcie_dev_attrs[] = {
>
> static struct attribute *pcibus_attrs[] = {
> &dev_attr_bus_rescan.attr,
> + &dev_attr_bus_reset.attr,
> &dev_attr_cpuaffinity.attr,
> &dev_attr_cpulistaffinity.attr,
> NULL,
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 7d85c04fbba2a..338dfcd983f1e 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5880,7 +5880,7 @@ EXPORT_SYMBOL_GPL(pci_probe_reset_bus);
> *
> * Same as above except return -EAGAIN if the bus cannot be locked
> */
> -static int __pci_reset_bus(struct pci_bus *bus)
> +int __pci_reset_bus(struct pci_bus *bus)
> {
> int rc;
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 14d00ce45bfa9..1cdc2c9547a7e 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -104,6 +104,7 @@ bool pci_reset_supported(struct pci_dev *dev);
> void pci_init_reset_methods(struct pci_dev *dev);
> int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
> int pci_bus_error_reset(struct pci_dev *dev);
> +int __pci_reset_bus(struct pci_bus *bus);
>
> struct pci_cap_saved_data {
> u16 cap_nr;
> --
> 2.43.5
>
