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>
master changeset: 92b8bc03bd4b582cb524db51494d0dba7607e7ac
master date: 2013-03-25 16:55:22 +0100

diff --git a/xen/drivers/passthrough/amd/iommu_acpi.c b/xen/drivers/passthrough/amd/iommu_acpi.c
index eb9c13cbb26f25ad1da73da4393262084e314fde..73524384c25409b8eb597ef256cd2d86b73a7ec3 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_acpi.c
+++ b/xen/drivers/passthrough/amd/iommu_acpi.c
@@ -664,6 +664,9 @@ static u16 __init parse_ivhd_device_special(
         return dev_length;
     }
 
+    if ( !iommu_intremap )
+        return dev_length;
+
     /*
      * Some BIOSes have IOAPIC broken entries so we check for IVRS
      * consistency here --- whether entry's IOAPIC ID is valid and
@@ -902,7 +905,7 @@ 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_registers[apic] ||
              ioapic_bdf[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 31acec9310ad38f7565e88319382da4d4049b9a7..fcb7e87f5fa11fc0a9c1e5535bac3ce373ce16af 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -971,7 +971,8 @@ 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;
 
     irq_to_iommu = xmalloc_array(struct amd_iommu *, nr_irqs);
@@ -991,7 +992,7 @@ 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 */