iommu/amd: Fix get_acpihid_device_id()

acpi_dev_hid_uid_match() expects a null pointer for UID if it doesn't
exist. The acpihid_map_entry contains a char buffer for holding the
UID. If no UID was provided in the IVRS table, this buffer will be
zeroed. If we pass in a null string, acpi_dev_hid_uid_match() will
return false because it will try and match an empty string to the ACPI
UID of the device.

Fixes: ae5e6c6439c3 ("iommu/amd: Switch to use acpi_dev_hid_uid_match()")
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200511103229.v2.1.I6f1b6f973ee6c8af1348611370c73a0ec0ea53f1@changeid
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 1dc3718..2883ac3 100644 (file)
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -127,7 +127,8 @@ static inline int get_acpihid_device_id(struct device *dev,
                return -ENODEV;
 
        list_for_each_entry(p, &acpihid_map, list) {
-               if (acpi_dev_hid_uid_match(adev, p->hid, p->uid)) {
+               if (acpi_dev_hid_uid_match(adev, p->hid,
+                                          p->uid[0] ? p->uid : NULL)) {
                        if (entry)
                                *entry = p;
                        return p->devid;