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Commit 468ff15a authored by Yijing Wang's avatar Yijing Wang Committed by Bjorn Helgaas
Browse files

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: default avatarYijing Wang <wangyijing@huawei.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent 48c3c38f

Documentation/ABI/testing/sysfs-bus-pci

+10 −0
Original line number Diff line number Diff line
@@ -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@vger.kernel.org>

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@tuxdriver.com>

drivers/pci/pci-sysfs.c

+19 −20
Original line number Diff line number Diff line
@@ -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);