[xen stable-4.13] AMD/IOMMU: ensure suitable ordering of DTE modifications

[patchbot@xxxxxxx]

commit e891c288ccf966a5822a6dd2dbf1342273a18d6e
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Oct 20 14:52:43 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Oct 20 14:52:43 2020 +0200

    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@xxxxxxxx>
    Reviewed-by: Paul Durrant <paul@xxxxxxx>
    master commit: 0514a3a25fb9ebff5d75cc8f00a9229385300858
    master date: 2020-10-20 14:23:12 +0200
---
 xen/drivers/passthrough/amd/iommu_map.c     | 8 ++++++++
 xen/drivers/passthrough/amd/pci_amd_iommu.c | 3 +++
 2 files changed, 11 insertions(+)

diff --git a/xen/drivers/passthrough/amd/iommu_map.c 
b/xen/drivers/passthrough/amd/iommu_map.c
index 7f8971c73c..85b8df9abd 100644
--- 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 5851cc5b18..46b1d367ec 100644
--- 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);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.13