> I propose the following, which rewords the changelog, documentation, and
> comments. It also adds a printk for the endpoint case and makes the bridge
> printk unconditional. And it simplifies the code to set the bus flag.
>
> Let me know if you object to anything.
Thanks a lot for optimizing the patch!
It's much better now.
Thanks!
Yijing.
>
> Bjorn
>
>
> commit 8ca0ecc79e6b154d3e16f443c1dd520f4c8af4ac
> Author: Yijing Wang <wangyijing@xxxxxxxxxx>
> Date: Tue Sep 23 13:27:24 2014 +0800
>
> PCI/MSI: Add "msi_bus" sysfs MSI/MSI-X control for endpoints
>
> The "msi_bus" sysfs file for bridges sets a bus flag to allow or disallow
> future driver requests for MSI or MSI-X. Previously, the sysfs file
> existed for endpoints but did nothing.
>
> Add "msi_bus" support for endpoints, so an administrator can prevent the
> use of MSI and MSI-X for individual devices.
>
> Note that as for bridges, these changes only affect future driver requests
> for MSI or MSI-X, so drivers may need to be reloaded.
>
> Add documentation for the "msi_bus" sysfs file.
>
> [bhelgaas: changelog, comments, add "subordinate", add endpoint printk,
> rework bus_flags setting, make bus_flags printk unconditional]
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index 6615fda0abfb..ee6c04036492 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -65,6 +65,16 @@ Description:
> force a rescan of all PCI buses in the system, and
> re-discover previously removed devices.
>
> +What: /sys/bus/pci/devices/.../msi_bus
> +Date: September 2014
> +Contact: Linux PCI developers <linux-pci@xxxxxxxxxxxxxxx>
> +Description:
> + Writing a zero value to this attribute disallows MSI and
> + MSI-X for any future drivers of the device. If the device
> + is a bridge, MSI and MSI-X will be disallowed for future
> + drivers of all child devices under the bridge. Drivers
> + must be reloaded for the new setting to take effect.
> +
> What: /sys/bus/pci/devices/.../msi_irqs/
> Date: September, 2011
> Contact: Neil Horman <nhorman@xxxxxxxxxxxxx>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 9ff0a901ecf7..dbf63e23988d 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -250,46 +250,45 @@ static ssize_t msi_bus_show(struct device *dev, struct device_attribute *attr,
> char *buf)
> {
> struct pci_dev *pdev = to_pci_dev(dev);
> + struct pci_bus *subordinate = pdev->subordinate;
>
> - if (!pdev->subordinate)
> - return 0;
> -
> - return sprintf(buf, "%u\n",
> - !(pdev->subordinate->bus_flags & PCI_BUS_FLAGS_NO_MSI));
> + return sprintf(buf, "%u\n", subordinate ?
> + !(subordinate->bus_flags & PCI_BUS_FLAGS_NO_MSI)
> + : !pdev->no_msi);
> }
>
> static ssize_t msi_bus_store(struct device *dev, struct device_attribute *attr,
> const char *buf, size_t count)
> {
> struct pci_dev *pdev = to_pci_dev(dev);
> + struct pci_bus *subordinate = pdev->subordinate;
> unsigned long val;
>
> if (kstrtoul(buf, 0, &val) < 0)
> return -EINVAL;
>
> - /*
> - * Bad things may happen if the no_msi flag is changed
> - * while drivers are loaded.
> - */
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> /*
> - * Maybe devices without subordinate buses shouldn't have this
> - * attribute in the first place?
> + * "no_msi" and "bus_flags" only affect what happens when a driver
> + * requests MSI or MSI-X. They don't affect any drivers that have
> + * already requested MSI or MSI-X.
> */
> - if (!pdev->subordinate)
> + if (!subordinate) {
> + pdev->no_msi = !val;
> + dev_info(&pdev->dev, "MSI/MSI-X %s for future drivers\n",
> + val ? "allowed" : "disallowed");
> return count;
> -
> - /* Is the flag going to change, or keep the value it already had? */
> - if (!(pdev->subordinate->bus_flags & PCI_BUS_FLAGS_NO_MSI) ^
> - !!val) {
> - pdev->subordinate->bus_flags ^= PCI_BUS_FLAGS_NO_MSI;
> -
> - dev_warn(&pdev->dev, "forced subordinate bus to%s support MSI, bad things could happen\n",
> - val ? "" : " not");
> }
>
> + if (val)
> + subordinate->bus_flags &= ~PCI_BUS_FLAGS_NO_MSI;
> + else
> + subordinate->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
> +
> + dev_info(&subordinate->dev, "MSI/MSI-X %s for future drivers of devices on this bus\n",
> + val ? "allowed" : "disallowed");
> return count;
> }
> static DEVICE_ATTR_RW(msi_bus);
>
> .
>
--
Thanks!
Yijing
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
