Some devices allow an individual function to be reset without affecting
other functions in the same device: that's what pci_reset_function does.
For devices that have this support, expose reset attribite in sysfs.
This is useful e.g. for virtualization, where a qemu userspace
process wants to reset the device when the guest is started/reset,
to emulate machine reboot as closely as possible.
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
Jesse, all,
could you please comment on whether the following approach looks sane?
Compile-tested only at this point. I'm also not sure whether the
CAP_SYS_ADMIN check is necessary: maybe 400 permissions on the sysfs
file are sufficient?
drivers/pci/pci-sysfs.c | 37 +++++++++++++++++++++++++++++++++++++
drivers/pci/pci.c | 16 ++++++++++++++++
drivers/pci/pci.h | 1 +
include/linux/kvm_host.h | 1 +
virt/kvm/irq_comm.c | 4 +++-
5 files changed, 58 insertions(+), 1 deletions(-)
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 85ebd02..92805e8 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -916,6 +916,28 @@ int __attribute__ ((weak)) pcibios_add_platform_entries(struct pci_dev *dev)
return 0;
}
+static ssize_t reset_store(struct device *dev,
+ struct device_attribute *attr, const char *buf,
+ size_t count)
+{
+ struct pci_dev *pdev = to_pci_dev(dev);
+ unsigned long val;
+ ssize_t result = strict_strtoul(buf, 0, &val);
+
+ if (result < 0)
+ return result;
+
+ /* this can crash the machine when done on the "wrong" device */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (val != 1)
+ return -EINVAL;
+ return pci_reset_function(pdev);
+}
+
+static struct device_attribute reset_attr = __ATTR(reset, 0200, NULL, reset_store);
+
static int pci_create_capabilities_sysfs(struct pci_dev *dev)
{
int retval;
@@ -943,7 +965,21 @@ static int pci_create_capabilities_sysfs(struct pci_dev *dev)
/* Active State Power Management */
pcie_aspm_create_sysfs_dev_files(dev);
+ if (!pci_probe_reset_function(dev)) {
+ retval = device_create_file(&dev->dev, &reset_attr);
+ if (retval)
+ goto error;
+ }
return 0;
+
+error:
+ pcie_aspm_remove_sysfs_dev_files(dev);
+ if (dev->vpd && dev->vpd->attr) {
+ sysfs_remove_bin_file(&dev->dev.kobj, dev->vpd->attr);
+ kfree(dev->vpd->attr);
+ }
+
+ return retval;
}
int __must_check pci_create_sysfs_dev_files (struct pci_dev *pdev)
@@ -1037,6 +1073,7 @@ static void pci_remove_capabilities_sysfs(struct pci_dev *dev)
}
pcie_aspm_remove_sysfs_dev_files(dev);
+ device_remove_file(&dev->dev, &reset_attr);
}
/**
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index dbd0f94..f6d1c6c 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2260,6 +2260,22 @@ int __pci_reset_function(struct pci_dev *dev)
EXPORT_SYMBOL_GPL(__pci_reset_function);
/**
+ * pci_probe_reset_function - check whether the device can be safely reset
+ * @dev: PCI device to reset
+ *
+ * Some devices allow an individual function to be reset without affecting
+ * other functions in the same device. The PCI device must be responsive
+ * to PCI config space in order to use this function.
+ *
+ * Returns 0 if the device function can be reset or negative if the
+ * device doesn't support resetting a single function.
+ */
+int pci_probe_reset_function(struct pci_dev *dev)
+{
+ return pci_dev_reset(dev, 1);
+}
+
+/**
* pci_reset_function - quiesce and reset a PCI device function
* @dev: PCI device to reset
*
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index f73bcbe..60a3811 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -16,6 +16,7 @@ extern void pci_cleanup_rom(struct pci_dev *dev);
extern int pci_mmap_fits(struct pci_dev *pdev, int resno,
struct vm_area_struct *vma);
#endif
+int pci_probe_reset_function(struct pci_dev *dev);
/**
* struct pci_platform_pm_ops - Firmware PM callbacks
--
1.6.2.5
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