AMD IOMMU: allow disabling only interrupt remapping when certain IVRS consistency...

After some more thought on the XSA-36 and specifically the comments we
got regarding disabling the IOMMU in this situation altogether making
things worse instead of better, I came to the conclusion that we can
actually restrict the action in affected cases to just disabling
interrupt remapping. That doesn't make the situation worse than prior
to the XSA-36 fixes (where interrupt remapping didn't really protect
domains from one another), but allows at least DMA isolation to still
be utilized.

To do so, disabling of interrupt remapping must be explicitly requested
on the command line - respective checks will then be skipped.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Suravee Suthikulanit <suravee.suthikulpanit@amd.com>

diff --git a/xen/drivers/passthrough/amd/iommu_acpi.c b/xen/drivers/passthrough/amd/iommu_acpi.c
index 8a6038cc86bbc9ac7c092f65af49107d4bda4a41..6a2cbb6190c1c909c8af7a61042cc9c0d7e51f38 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_acpi.c
+++ b/xen/drivers/passthrough/amd/iommu_acpi.c
@@ -659,6 +659,8 @@ static u16 __init parse_ivhd_device_special(
     switch ( special->variety )
     {
     case ACPI_IVHD_IOAPIC:
+        if ( !iommu_intremap )
+            break;
         /*
          * Some BIOSes have IOAPIC broken entries so we check for IVRS
          * consistency here --- whether entry's IOAPIC ID is valid and
@@ -921,7 +923,7 @@ static int __init parse_ivrs_table(struct acpi_table_header *table)
     }
 
     /* Each IO-APIC must have been mentioned in the table. */
-    for ( apic = 0; !error && apic < nr_ioapics; ++apic )
+    for ( apic = 0; !error && iommu_intremap && apic < nr_ioapics; ++apic )
     {
         if ( !nr_ioapic_entries[apic] ||
              ioapic_sbdf[IO_APIC_ID(apic)].pin_setup )

diff --git a/xen/drivers/passthrough/amd/iommu_init.c b/xen/drivers/passthrough/amd/iommu_init.c
index e0986d85d1c601b7c57dd60dcf89321d51f6fe5d..73d9ce46667b0113e1a5a3435572355db901ac94 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -1194,7 +1194,8 @@ int __init amd_iommu_init(void)
 
     BUG_ON( !iommu_found() );
 
-    if ( amd_iommu_perdev_intremap && amd_sp5100_erratum28() )
+    if ( iommu_intremap && amd_iommu_perdev_intremap &&
+         amd_sp5100_erratum28() )
         goto error_out;
 
     ivrs_bdf_entries = amd_iommu_get_ivrs_dev_entries();
@@ -1211,7 +1212,7 @@ int __init amd_iommu_init(void)
         goto error_out;
 
     /* initialize io-apic interrupt remapping entries */
-    if ( amd_iommu_setup_ioapic_remapping() != 0 )
+    if ( iommu_intremap && amd_iommu_setup_ioapic_remapping() != 0 )
         goto error_out;
 
     /* allocate and initialize a global device table shared by all iommus */