iommu/amd-vi: flush IOMMU TLB when flushing the DTE

The caching invalidation guidelines from the AMD-Vi specification (48882—Rev
3.07-PUB—Oct 2022) seem to be misleading on some hardware, as devices will
malfunction (see stale DMA mappings) if some fields of the DTE are updated but
the IOMMU TLB is not flushed. This has been observed in practice on AMD
systems.  Due to the lack of guidance from the currently published
specification this patch aims to increase the flushing done in order to prevent
device malfunction.

In order to fix, issue an INVALIDATE_IOMMU_PAGES command from
amd_iommu_flush_device(), flushing all the address space.  Note this requires
callers to be adjusted in order to pass the DomID on the DTE previous to the
modification.

Some call sites don't provide a valid DomID to amd_iommu_flush_device() in
order to avoid the flush.  That's because the device had address translations
disabled and hence the previous DomID on the DTE is not valid.  Note the
current logic relies on the entity disabling address translations to also flush
the TLB of the in use DomID.

Device I/O TLB flushing when ATS are enabled is not covered by the current
change, as ATS usage is not security supported.

This is XSA-442 / CVE-2023-34326

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit 5fc98b97084a46884acef9320e643faf40d42212)

diff --git a/xen/drivers/passthrough/amd/iommu.h b/xen/drivers/passthrough/amd/iommu.h
index 3c702eb5179f3292909c14085c7857f1cd3a92c5..6dd24593a001990afa8adbb1666432f367d51812 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu.h
+++ b/xen/drivers/passthrough/amd/iommu.h
@@ -280,7 +280,8 @@ void amd_iommu_flush_pages(struct domain *d, unsigned long dfn,
                            unsigned int order);
 void amd_iommu_flush_iotlb(u8 devfn, const struct pci_dev *pdev,
                            uint64_t gaddr, unsigned int order);
-void amd_iommu_flush_device(struct amd_iommu *iommu, uint16_t bdf);
+void amd_iommu_flush_device(struct amd_iommu *iommu, uint16_t bdf,
+                            domid_t domid);
 void amd_iommu_flush_intremap(struct amd_iommu *iommu, uint16_t bdf);
 void amd_iommu_flush_all_caches(struct amd_iommu *iommu);
 

diff --git a/xen/drivers/passthrough/amd/iommu_cmd.c b/xen/drivers/passthrough/amd/iommu_cmd.c
index 809d93b89f8f2e55d61af0d52c114782a82544a5..41a32c757bf0a45c699e789ceda04d27782ba813 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_cmd.c
+++ b/xen/drivers/passthrough/amd/iommu_cmd.c
@@ -362,10 +362,18 @@ void amd_iommu_flush_pages(struct domain *d,
     _amd_iommu_flush_pages(d, __dfn_to_daddr(dfn), order);
 }
 
-void amd_iommu_flush_device(struct amd_iommu *iommu, uint16_t bdf)
+void amd_iommu_flush_device(struct amd_iommu *iommu, uint16_t bdf,
+                            domid_t domid)
 {
     invalidate_dev_table_entry(iommu, bdf);
     flush_command_buffer(iommu, 0);
+
+    /* Also invalidate IOMMU TLB entries when flushing the DTE. */
+    if ( domid != DOMID_INVALID )
+    {
+        invalidate_iommu_pages(iommu, INV_IOMMU_ALL_PAGES_ADDRESS, domid, 0);
+        flush_command_buffer(iommu, 0);
+    }
 }
 
 void amd_iommu_flush_intremap(struct amd_iommu *iommu, uint16_t bdf)

diff --git a/xen/drivers/passthrough/amd/iommu_guest.c b/xen/drivers/passthrough/amd/iommu_guest.c
index 85828490ffee447c689ea1304fcf132137823242..38c7b4d979a9e89bbe937aa8ff2add7a262cafbe 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_guest.c
+++ b/xen/drivers/passthrough/amd/iommu_guest.c
@@ -385,7 +385,7 @@ static int do_completion_wait(struct domain *d, cmd_entry_t *cmd)
 
 static int do_invalidate_dte(struct domain *d, cmd_entry_t *cmd)
 {
-    uint16_t gbdf, mbdf, req_id, gdom_id, hdom_id;
+    uint16_t gbdf, mbdf, req_id, gdom_id, hdom_id, prev_domid;
     struct amd_iommu_dte *gdte, *mdte, *dte_base;
     struct amd_iommu *iommu = NULL;
     struct guest_iommu *g_iommu;
@@ -445,13 +445,14 @@ static int do_invalidate_dte(struct domain *d, cmd_entry_t *cmd)
     req_id = get_dma_requestor_id(iommu->seg, mbdf);
     dte_base = iommu->dev_table.buffer;
     mdte = &dte_base[req_id];
+    prev_domid = mdte->domain_id;
 
     spin_lock_irqsave(&iommu->lock, flags);
     dte_set_gcr3_table(mdte, hdom_id, gcr3_mfn << PAGE_SHIFT, gv, glx);
 
     spin_unlock_irqrestore(&iommu->lock, flags);
 
-    amd_iommu_flush_device(iommu, req_id);
+    amd_iommu_flush_device(iommu, req_id, prev_domid);
 
     return 0;
 }

diff --git a/xen/drivers/passthrough/amd/iommu_init.c b/xen/drivers/passthrough/amd/iommu_init.c
index ca791d4e54a731039a30599791b37f814d3ad911..7dfe4b15dc331fa83850f58deea8aa5ec47d9abf 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -1556,7 +1556,11 @@ static int _invalidate_all_devices(
         req_id = ivrs_mappings[bdf].dte_requestor_id;
         if ( iommu )
         {
-            amd_iommu_flush_device(iommu, req_id);
+            /*
+             * IOMMU TLB flush performed separately (see
+             * invalidate_all_domain_pages()).
+             */
+            amd_iommu_flush_device(iommu, req_id, DOMID_INVALID);
             amd_iommu_flush_intremap(iommu, req_id);
         }
     }

diff --git a/xen/drivers/passthrough/amd/pci_amd_iommu.c b/xen/drivers/passthrough/amd/pci_amd_iommu.c
index e5e0f0040288aa0146c98cdd0be23dc553e53726..7b6dbf546adcdaf290bf2d060a404252fde4ebea 100644 (file)
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -192,10 +192,13 @@ static int __must_check amd_iommu_setup_domain_device(
 
         spin_unlock_irqrestore(&iommu->lock, flags);
 
-        amd_iommu_flush_device(iommu, req_id);
+        /* DTE didn't have DMA translations enabled, do not flush the TLB. */
+        amd_iommu_flush_device(iommu, req_id, DOMID_INVALID);
     }
     else if ( dte->pt_root != mfn_x(page_to_mfn(root_pg)) )
     {
+        domid_t prev_domid = dte->domain_id;
+
         /*
          * Strictly speaking if the device is the only one with this requestor
          * ID, it could be allowed to be re-assigned regardless of unity map
@@ -252,7 +255,7 @@ static int __must_check amd_iommu_setup_domain_device(
 
         spin_unlock_irqrestore(&iommu->lock, flags);
 
-        amd_iommu_flush_device(iommu, req_id);
+        amd_iommu_flush_device(iommu, req_id, prev_domid);
     }
     else
         spin_unlock_irqrestore(&iommu->lock, flags);
@@ -421,6 +424,8 @@ static void amd_iommu_disable_domain_device(const struct domain *domain,
     spin_lock_irqsave(&iommu->lock, flags);
     if ( dte->tv || dte->v )
     {
+        domid_t prev_domid = dte->domain_id;
+
         /* See the comment in amd_iommu_setup_device_table(). */
         dte->int_ctl = IOMMU_DEV_TABLE_INT_CONTROL_ABORTED;
         smp_wmb();
@@ -439,7 +444,7 @@ static void amd_iommu_disable_domain_device(const struct domain *domain,
 
         spin_unlock_irqrestore(&iommu->lock, flags);
 
-        amd_iommu_flush_device(iommu, req_id);
+        amd_iommu_flush_device(iommu, req_id, prev_domid);
 
         AMD_IOMMU_DEBUG("Disable: device id = %#x, "
                         "domain = %d, paging mode = %d\n",
@@ -611,7 +616,8 @@ static int amd_iommu_add_device(u8 devfn, struct pci_dev *pdev)
 
         spin_unlock_irqrestore(&iommu->lock, flags);
 
-        amd_iommu_flush_device(iommu, bdf);
+        /* DTE didn't have DMA translations enabled, do not flush the TLB. */
+        amd_iommu_flush_device(iommu, bdf, DOMID_INVALID);
     }
 
     if ( amd_iommu_reserve_domain_unity_map(