iommu/amd: Work around wrong IOAPIC device-id in IVRS table

On some systems the BIOS puts the wrong device-id for the
IO-APIC into the IVRS table. The result is that interrupt
remapping is not working for the IO-APIC irqs. This usually
means a kernel panic at boot because the timer is not
working.
Fix this kernel panic by disabling interrupt remapping if
this problem is discovered in the IVRS table.

Reported-by: Andrew Oakley <andrew@ado.is-a-geek.net>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 32 insertions, 7 deletions

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 18b0d99bd4d..81837b0710a 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -1599,21 +1599,46 @@ static void __init free_on_init_error(void)
 #endif
 }
 
+/* SB IOAPIC is always on this device in AMD systems */
+#define IOAPIC_SB_DEVID         ((0x00 << 8) | PCI_DEVFN(0x14, 0))
+
 static bool __init check_ioapic_information(void)
 {
+        bool ret, has_sb_ioapic;
         int idx;
 
-        for (idx = 0; idx < nr_ioapics; idx++) {
-                int id = mpc_ioapic_id(idx);
+        has_sb_ioapic = false;
+        ret           = false;
 
-                if (get_ioapic_devid(id) < 0) {
-                        pr_err(FW_BUG "AMD-Vi: IO-APIC[%d] not in IVRS table\n", id);
-                        pr_err("AMD-Vi: Disabling interrupt remapping due to BIOS Bug\n");
-                        return false;
+        for (idx = 0; idx < nr_ioapics; idx++) {
+                int devid, id = mpc_ioapic_id(idx);
+
+                devid = get_ioapic_devid(id);
+                if (devid < 0) {
+                        pr_err(FW_BUG "AMD-Vi: IOAPIC[%d] not in IVRS table\n", id);
+                        ret = false;
+                } else if (devid == IOAPIC_SB_DEVID) {
+                        has_sb_ioapic = true;
+                        ret           = true;
                 }
         }
 
-        return true;
+        if (!has_sb_ioapic) {
+                /*
+                 * We expect the SB IOAPIC to be listed in the IVRS
+                 * table. The system timer is connected to the SB IOAPIC
+                 * and if we don't have it in the list the system will
+                 * panic at boot time.  This situation usually happens
+                 * when the BIOS is buggy and provides us the wrong
+                 * device id for the IOAPIC in the system.
+                 */
+                pr_err(FW_BUG "AMD-Vi: No southbridge IOAPIC found in IVRS table\n");
+        }
+
+        if (!ret)
+                pr_err("AMD-Vi: Disabling interrupt remapping due to BIOS Bug(s)\n");
+
+        return ret;
 }
 
 static void __init free_dma_resources(void)