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@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 9ff0a90..dbf63e2 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -250,46 +250,45 @@
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);