[Xen-devel] [PATCH v6 8/8] AMD/IOMMU: pre-fill all DTEs right after table allocation

[Jan Beulich <jbeulich@xxxxxxxx>]

Make sure we don't leave any DTEs unexpected requests through which
would be passed through untranslated. Set V and IV right away (with
all other fields left as zero), relying on the V and/or IV bits
getting cleared only by amd_iommu_set_root_page_table() and
amd_iommu_set_intremap_table() under special pass-through circumstances.
Switch back to initial settings in amd_iommu_disable_domain_device().

Take the liberty and also make the latter function static, constifying
its first parameter at the same time, at this occasion.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v6: New.

---
 xen/drivers/passthrough/amd/iommu_init.c    |   22 +++++++++++++++++++---
 xen/drivers/passthrough/amd/pci_amd_iommu.c |   20 ++++++++++++++++----
 2 files changed, 35 insertions(+), 7 deletions(-)

--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -1255,12 +1255,28 @@ static int __init amd_iommu_setup_device
 
     if ( !dt )
     {
+        unsigned int size = dt_alloc_size();
+
         /* allocate 'device table' on a 4K boundary */
         dt = IVRS_MAPPINGS_DEVTAB(ivrs_mappings) =
-            allocate_buffer(dt_alloc_size(), "Device Table");
+            allocate_buffer(size, "Device Table");
+        if ( !dt )
+            return -ENOMEM;
+
+        /*
+         * Prefill every DTE such that all kinds of requests will get aborted.
+         * Besides the two bits set to true below this builds upon
+         * IOMMU_DEV_TABLE_SYS_MGT_DMA_ABORTED,
+         * IOMMU_DEV_TABLE_IO_CONTROL_ABORTED, as well as
+         * IOMMU_DEV_TABLE_INT_CONTROL_ABORTED all being zero, and us also
+         * wanting at least TV, GV, I, and EX set to false.
+         */
+        for ( bdf = 0, size /= sizeof(*dt); bdf < size; ++bdf )
+        {
+            dt[bdf].v = true;
+            dt[bdf].iv = true;
+        }
     }
-    if ( !dt )
-        return -ENOMEM;
 
     /* Add device table entries */
     for ( bdf = 0; bdf < ivrs_bdf_entries; bdf++ )
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -267,9 +267,9 @@ static void __hwdom_init amd_iommu_hwdom
     setup_hwdom_pci_devices(d, amd_iommu_add_device);
 }
 
-void amd_iommu_disable_domain_device(struct domain *domain,
-                                     struct amd_iommu *iommu,
-                                     u8 devfn, struct pci_dev *pdev)
+static void amd_iommu_disable_domain_device(const struct domain *domain,
+                                            struct amd_iommu *iommu,
+                                            uint8_t devfn, struct pci_dev 
*pdev)
 {
     struct amd_iommu_dte *table, *dte;
     unsigned long flags;
@@ -284,9 +284,21 @@ void amd_iommu_disable_domain_device(str
     spin_lock_irqsave(&iommu->lock, flags);
     if ( dte->tv || dte->v )
     {
+        /* See the comment in amd_iommu_setup_device_table(). */
+        dte->int_ctl = IOMMU_DEV_TABLE_INT_CONTROL_ABORTED;
+        smp_wmb();
+        dte->iv = true;
         dte->tv = false;
-        dte->v = false;
+        dte->gv = false;
         dte->i = false;
+        dte->ex = false;
+        dte->sa = false;
+        dte->se = false;
+        dte->sd = false;
+        dte->sys_mgt = IOMMU_DEV_TABLE_SYS_MGT_DMA_ABORTED;
+        dte->ioctl = IOMMU_DEV_TABLE_IO_CONTROL_ABORTED;
+        smp_wmb();
+        dte->v = true;
 
         amd_iommu_flush_device(iommu, req_id);
 


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