[xen stable-4.10] AMD/IOMMU: ensure suitable ordering of DTE modifications

[patchbot@xxxxxxx]

commit 71da63bbb83af8c8c537f3731dda7dc2d2fd31ac
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Oct 20 15:21:40 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Oct 20 15:21:40 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 | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/xen/drivers/passthrough/amd/iommu_map.c 
b/xen/drivers/passthrough/amd/iommu_map.c
index 3c29788d9a..f0bc1dd3af 100644
--- a/xen/drivers/passthrough/amd/iommu_map.c
+++ b/xen/drivers/passthrough/amd/iommu_map.c
@@ -147,7 +147,22 @@ void amd_iommu_set_root_page_table(
     u32 *dte, u64 root_ptr, u16 domain_id, u8 paging_mode, u8 valid)
 {
     u64 addr_hi, addr_lo;
-    u32 entry;
+    u32 entry, dte0 = dte[0];
+
+    if ( valid ||
+         get_field_from_reg_u32(dte0, IOMMU_DEV_TABLE_VALID_MASK,
+                                IOMMU_DEV_TABLE_VALID_SHIFT) )
+    {
+        set_field_in_reg_u32(IOMMU_CONTROL_DISABLED, dte0,
+                             IOMMU_DEV_TABLE_TRANSLATION_VALID_MASK,
+                             IOMMU_DEV_TABLE_TRANSLATION_VALID_SHIFT, &dte0);
+        set_field_in_reg_u32(IOMMU_CONTROL_ENABLED, dte0,
+                             IOMMU_DEV_TABLE_VALID_MASK,
+                             IOMMU_DEV_TABLE_VALID_SHIFT, &dte0);
+        dte[0] = dte0;
+        smp_wmb();
+    }
+
     set_field_in_reg_u32(domain_id, 0,
                          IOMMU_DEV_TABLE_DOMAIN_ID_MASK,
                          IOMMU_DEV_TABLE_DOMAIN_ID_SHIFT, &entry);
@@ -166,8 +181,9 @@ void amd_iommu_set_root_page_table(
                          IOMMU_DEV_TABLE_IO_READ_PERMISSION_MASK,
                          IOMMU_DEV_TABLE_IO_READ_PERMISSION_SHIFT, &entry);
     dte[1] = entry;
+    smp_wmb();
 
-    set_field_in_reg_u32((u32)addr_lo >> PAGE_SHIFT, 0,
+    set_field_in_reg_u32((u32)addr_lo >> PAGE_SHIFT, dte0,
                          IOMMU_DEV_TABLE_PAGE_TABLE_PTR_LOW_MASK,
                          IOMMU_DEV_TABLE_PAGE_TABLE_PTR_LOW_SHIFT, &entry);
     set_field_in_reg_u32(paging_mode, entry,
@@ -180,7 +196,7 @@ void amd_iommu_set_root_page_table(
                          IOMMU_CONTROL_DISABLED, entry,
                          IOMMU_DEV_TABLE_VALID_MASK,
                          IOMMU_DEV_TABLE_VALID_SHIFT, &entry);
-    dte[0] = entry;
+    write_atomic(&dte[0], entry);
 }
 
 void iommu_dte_set_iotlb(u32 *dte, u8 i)
@@ -212,6 +228,7 @@ void __init amd_iommu_set_intremap_table(
                         IOMMU_DEV_TABLE_INT_CONTROL_MASK,
                         IOMMU_DEV_TABLE_INT_CONTROL_SHIFT, &entry);
     dte[5] = entry;
+    smp_wmb();
 
     set_field_in_reg_u32((u32)addr_lo >> 6, 0,
                         IOMMU_DEV_TABLE_INT_TABLE_PTR_LOW_MASK,
@@ -229,7 +246,7 @@ void __init amd_iommu_set_intremap_table(
                          IOMMU_CONTROL_DISABLED, entry,
                          IOMMU_DEV_TABLE_INT_VALID_MASK,
                          IOMMU_DEV_TABLE_INT_VALID_SHIFT, &entry);
-    dte[4] = entry;
+    write_atomic(&dte[4], entry);
 }
 
 void __init iommu_dte_add_device_entry(u32 *dte, struct ivrs_mappings 
*ivrs_dev)
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.10