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Re: [libvirt] [PATCH 03/18] virpcimock: Create driver_override file in device dirs



Reviewed-by: Daniel Henrique Barboza <danielhb413 gmail com>

On 8/14/19 8:57 AM, Michal Privoznik wrote:
Newer kernels (v3.16-rc1~29^2~6^4) have 'driver_override' file
which simplifies way of binding a PCI device to desired driver.
Libvirt has support for this for some time too (v2.3.0-rc1~236),
but not our virpcimock. So far we did not care because our code
is designed to deal with this situation. Except for one.
hypothetical case: binding a device to the vfio-pci driver can be
successful only via driver_override. Any attempt to bind a PCI
device to vfio-pci driver using old method (new_id + unbind +
bind) will fail because of b803b29c1a5. While on vanilla kernel
I'm able to use the old method successfully, it's failing on RHEL
kernels (not sure why).

Signed-off-by: Michal Privoznik <mprivozn redhat com>
---
  tests/virpcimock.c | 52 ++++++++++++++++++++++++++++++++++++++++------
  1 file changed, 46 insertions(+), 6 deletions(-)

diff --git a/tests/virpcimock.c b/tests/virpcimock.c
index 6865f992dc..1c21e4e045 100644
--- a/tests/virpcimock.c
+++ b/tests/virpcimock.c
@@ -87,6 +87,11 @@ char *fakesysfspcidir;
   *   Probe for a driver that handles the specified device.
   *   Data in format "DDDD:BB:DD.F" (Domain:Bus:Device.Function).
   *
+ * /sys/bus/pci/devices/<device>/driver_override
+ *   Name of a driver that overrides preferred driver can be written
+ *   here. The device will be attached to it on drivers_probe event.
+ *   Writing an empty string (or "\n") clears the override.
+ *
   * As a little hack, we are not mocking write to these files, but close()
   * instead. The advantage is we don't need any self growing array to hold the
   * partial writes and construct them back. We can let all the writes finish,
@@ -147,6 +152,7 @@ static struct pciDevice *pci_device_find_by_content(const char *path);
  static void pci_driver_new(const char *name, int fail, ...);
  static struct pciDriver *pci_driver_find_by_dev(struct pciDevice *dev);
  static struct pciDriver *pci_driver_find_by_path(const char *path);
+static struct pciDriver *pci_driver_find_by_driver_override(struct pciDevice *dev);
  static int pci_driver_bind(struct pciDriver *driver, struct pciDevice *dev);
  static int pci_driver_unbind(struct pciDriver *driver, struct pciDevice *dev);
  static int pci_driver_handle_change(int fd, const char *path);
@@ -202,7 +208,8 @@ make_symlink(const char *path,
  static int
  pci_read_file(const char *path,
                char *buf,
-              size_t buf_size)
+              size_t buf_size,
+              bool truncate)
  {
      int ret = -1;
      int fd = -1;
@@ -224,7 +231,8 @@ pci_read_file(const char *path,
          goto cleanup;
      }
- if (ftruncate(fd, 0) < 0)
+    if (truncate &&
+        ftruncate(fd, 0) < 0)
          goto cleanup;
ret = 0;
@@ -398,6 +406,8 @@ pci_device_new_from_stub(const struct pciDevice *data)
          ABORT("@tmp overflow");
      make_file(devpath, "class", tmp, -1);
+ make_file(devpath, "driver_override", NULL, -1);
+
      if (snprintf(tmp, sizeof(tmp),
                   "%s/../../../kernel/iommu_groups/%d",
                   devpath, dev->iommuGroup) < 0) {
@@ -441,7 +451,7 @@ pci_device_find_by_content(const char *path)
  {
      char tmp[32];
- if (pci_read_file(path, tmp, sizeof(tmp)) < 0)
+    if (pci_read_file(path, tmp, sizeof(tmp), true) < 0)
          return NULL;
return pci_device_find_by_id(tmp);
@@ -450,7 +460,10 @@ pci_device_find_by_content(const char *path)
  static int
  pci_device_autobind(struct pciDevice *dev)
  {
-    struct pciDriver *driver = pci_driver_find_by_dev(dev);
+    struct pciDriver *driver = pci_driver_find_by_driver_override(dev);
+
+    if (!driver)
+        driver = pci_driver_find_by_dev(dev);
if (!driver) {
          /* No driver found. Nothing to do */
@@ -544,6 +557,31 @@ pci_driver_find_by_path(const char *path)
      return NULL;
  }
+static struct pciDriver *
+pci_driver_find_by_driver_override(struct pciDevice *dev)
+{
+    VIR_AUTOFREE(char *) path = NULL;
+    char tmp[32];
+    size_t i;
+
+    if (virAsprintfQuiet(&path,
+                         SYSFS_PCI_PREFIX "devices/%s/driver_override",
+                         dev->id) < 0)
+        return NULL;
+
+    if (pci_read_file(path, tmp, sizeof(tmp), false) < 0)
+        return NULL;
+
+    for (i = 0; i < nPCIDrivers; i++) {
+        struct pciDriver *driver = pciDrivers[i];
+
+        if (STREQ(tmp, driver->name))
+            return driver;
+    }
+
+    return NULL;
+}
+
  static int
  pci_driver_bind(struct pciDriver *driver,
                  struct pciDevice *dev)
@@ -657,6 +695,8 @@ pci_driver_handle_change(int fd ATTRIBUTE_UNUSED, const char *path)
          ret = pci_driver_handle_remove_id(path);
      else if (STREQ(file, "drivers_probe"))
          ret = pci_driver_handle_drivers_probe(path);
+    else if (STREQ(file, "driver_override"))
+        ret = 0; /* nada */
      else
          ABORT("Not handled write to: %s", path);
      return ret;
@@ -711,7 +751,7 @@ pci_driver_handle_new_id(const char *path)
          goto cleanup;
      }
- if (pci_read_file(path, buf, sizeof(buf)) < 0)
+    if (pci_read_file(path, buf, sizeof(buf), true) < 0)
          goto cleanup;
if (sscanf(buf, "%x %x", &vendor, &device) < 2) {
@@ -766,7 +806,7 @@ pci_driver_handle_remove_id(const char *path)
          goto cleanup;
      }
- if (pci_read_file(path, buf, sizeof(buf)) < 0)
+    if (pci_read_file(path, buf, sizeof(buf), true) < 0)
          goto cleanup;
if (sscanf(buf, "%x %x", &vendor, &device) < 2) {


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