iommu/vt-d: Search for ACPI _DSM method for DMAR hotplug

According to Intel VT-d specification, _DSM method to support DMAR
hotplug should exist directly under corresponding ACPI object
representing PCI host bridge. But some BIOSes doesn't conform to
this, so search for _DSM method in the subtree starting from the
ACPI object representing the PCI host bridge.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Reviewed-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 30 insertions, 3 deletions

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 0bd536d769a9..9847613085e1 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1942,21 +1942,48 @@ static int dmar_hotplug_remove(acpi_handle handle)
         return ret;
 }
 
+static acpi_status dmar_get_dsm_handle(acpi_handle handle, u32 lvl,
+                                       void *context, void **retval)
+{
+        acpi_handle *phdl = retval;
+
+        if (dmar_detect_dsm(handle, DMAR_DSM_FUNC_DRHD)) {
+                *phdl = handle;
+                return AE_CTRL_TERMINATE;
+        }
+
+        return AE_OK;
+}
+
 static int dmar_device_hotplug(acpi_handle handle, bool insert)
 {
         int ret;
+        acpi_handle tmp = NULL;
+        acpi_status status;
 
         if (!dmar_in_use())
                 return 0;
 
-        if (!dmar_detect_dsm(handle, DMAR_DSM_FUNC_DRHD))
+        if (dmar_detect_dsm(handle, DMAR_DSM_FUNC_DRHD)) {
+                tmp = handle;
+        } else {
+                status = acpi_walk_namespace(ACPI_TYPE_DEVICE, handle,
+                                             ACPI_UINT32_MAX,
+                                             dmar_get_dsm_handle,
+                                             NULL, NULL, &tmp);
+                if (ACPI_FAILURE(status)) {
+                        pr_warn("Failed to locate _DSM method.\n");
+                        return -ENXIO;
+                }
+        }
+        if (tmp == NULL)
                 return 0;
 
         down_write(&dmar_global_lock);
         if (insert)
-                ret = dmar_hotplug_insert(handle);
+                ret = dmar_hotplug_insert(tmp);
         else
-                ret = dmar_hotplug_remove(handle);
+                ret = dmar_hotplug_remove(tmp);
         up_write(&dmar_global_lock);
 
         return ret;