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>

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 18b0d99..81837b0 100644 (file)
--- 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)