AMD/IOMMU: ensure suitable ordering of DTE modifications

DMA and interrupt translation should be enabled only after other
applicable DTE fields have been written. Similarly when disabling
translation or when moving a device between domains, translation should
first be disabled, before other entry fields get modified. Note however
that the "moving" aspect doesn't apply to the interrupt remapping side,
as domain specifics are maintained in the IRTEs here, not the DTE. We
also never disable interrupt remapping once it got enabled for a device
(the respective argument passed is always the immutable iommu_intremap).

This is part of XSA-347.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul@xen.org>
master commit: 0514a3a25fb9ebff5d75cc8f00a9229385300858
master date: 2020-10-20 14:23:12 +0200

diff --git a/xen/drivers/passthrough/amd/iommu_map.c b/xen/drivers/passthrough/amd/iommu_map.c
index 7f8971c73c5927422c6319358f7c06fe48dea4bb..85b8df9abd8873165fbca716e0095b1176e67fb5 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_map.c
+++ b/xen/drivers/passthrough/amd/iommu_map.c
@@ -107,11 +107,18 @@ void amd_iommu_set_root_page_table(struct amd_iommu_dte *dte,
                                    uint64_t root_ptr, uint16_t domain_id,
                                    uint8_t paging_mode, bool valid)
 {
+    if ( valid || dte->v )
+    {
+        dte->tv = false;
+        dte->v = true;
+        smp_wmb();
+    }
     dte->domain_id = domain_id;
     dte->pt_root = paddr_to_pfn(root_ptr);
     dte->iw = true;
     dte->ir = true;
     dte->paging_mode = paging_mode;
+    smp_wmb();
     dte->tv = true;
     dte->v = valid;
 }
@@ -134,6 +141,7 @@ void amd_iommu_set_intremap_table(
     }
 
     dte->ig = false; /* unmapped interrupts result in i/o page faults */
+    smp_wmb();
     dte->iv = valid;
 }
 

diff --git a/xen/drivers/passthrough/amd/pci_amd_iommu.c b/xen/drivers/passthrough/amd/pci_amd_iommu.c
index 5851cc5b18b936855920affa1ede2dfbc6262a79..46b1d367ecfafd2ed63a1770d22b284af32a3c55 100644 (file)
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -120,7 +120,10 @@ static void amd_iommu_setup_domain_device(
         /* Undo what amd_iommu_disable_domain_device() may have done. */
         ivrs_dev = &get_ivrs_mappings(iommu->seg)[req_id];
         if ( dte->it_root )
+        {
             dte->int_ctl = IOMMU_DEV_TABLE_INT_CONTROL_TRANSLATED;
+            smp_wmb();
+        }
         dte->iv = iommu_intremap;
         dte->ex = ivrs_dev->dte_allow_exclusion;
         dte->sys_mgt = MASK_EXTR(ivrs_dev->device_flags, ACPI_IVHD_SYSTEM_MGMT);