[Xen-devel] [PATCH v8 7/8] Revert "xen/arm: introduce XENFEAT_grant_map_identity"

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Revert commit id 8d09ef6906ca0a9957e21334ad2c3eed626abe63.
Just keep the definition of XENFEAT_grant_map_identity.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Reviewed-by: Julien Grall <julien.grall@xxxxxxxxxx>

---

Changes in v2:

- comment out the definition of XENFEAT_grant_map_identity.
---
 xen/common/grant_table.c           |   30 +++++-------------------------
 xen/common/kernel.c                |    2 --
 xen/drivers/passthrough/arm/smmu.c |   33 +++++++++++++++++++++++++++++++++
 xen/include/asm-arm/grant_table.h  |    3 ++-
 xen/include/public/features.h      |    4 +++-
 5 files changed, 43 insertions(+), 29 deletions(-)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index c56ad5e..d53f627 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -779,23 +779,13 @@ __gnttab_map_grant_ref(
              !(old_pin & (GNTPIN_hstw_mask|GNTPIN_devw_mask)) )
         {
             if ( wrc == 0 )
-            {
-                if ( is_domain_direct_mapped(ld) )
-                    err = arch_grant_map_page_identity(ld, frame, 1);
-                else
-                    err = iommu_map_page(ld, frame, frame,
-                            IOMMUF_readable|IOMMUF_writable);
-            }
+                err = iommu_map_page(ld, frame, frame,
+                                     IOMMUF_readable|IOMMUF_writable);
         }
         else if ( act_pin && !old_pin )
         {
             if ( (wrc + rdc) == 0 )
-            {
-                if ( is_domain_direct_mapped(ld) )
-                    err = arch_grant_map_page_identity(ld, frame, 0);
-                else
-                    err = iommu_map_page(ld, frame, frame, IOMMUF_readable);
-            }
+                err = iommu_map_page(ld, frame, frame, IOMMUF_readable);
         }
         if ( err )
         {
@@ -992,19 +982,9 @@ __gnttab_unmap_common(
         int err = 0;
         mapcount(lgt, rd, op->frame, &wrc, &rdc);
         if ( (wrc + rdc) == 0 )
-        {
-            if ( is_domain_direct_mapped(ld) )
-                err = arch_grant_unmap_page_identity(ld, op->frame);
-            else
-                err = iommu_unmap_page(ld, op->frame);
-        }
+            err = iommu_unmap_page(ld, op->frame);
         else if ( wrc == 0 )
-        {
-            if ( is_domain_direct_mapped(ld) )
-                err = arch_grant_map_page_identity(ld, op->frame, 0);
-            else
-                err = iommu_map_page(ld, op->frame, op->frame, 
IOMMUF_readable);
-        }
+            err = iommu_map_page(ld, op->frame, op->frame, IOMMUF_readable);
         if ( err )
         {
             rc = GNTST_general_error;
diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index ce65486..d23c422 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -332,8 +332,6 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
                 break;
             }
 #endif
-            if ( is_domain_direct_mapped(d) )
-                fi.submap |= 1U << XENFEAT_grant_map_identity;
             break;
         default:
             return -EINVAL;
diff --git a/xen/drivers/passthrough/arm/smmu.c 
b/xen/drivers/passthrough/arm/smmu.c
index 3cbd206..9a95ac9 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -1536,6 +1536,37 @@ static void arm_smmu_iommu_domain_teardown(struct domain 
*d)
     xfree(smmu_domain);
 }
 
+static int arm_smmu_map_page(struct domain *d, unsigned long gfn,
+                             unsigned long mfn, unsigned int flags)
+{
+    /* Grant mappings can be used for DMA requests. The dev_bus_addr returned 
by
+     * the hypercall is the MFN (not the IPA). For device protected by
+     * an IOMMU, Xen needs to add a 1:1 mapping in the domain p2m to
+     * allow DMA request to work.
+     * This is only valid when the domain is directed mapped. Hence this
+     * function should only be used by gnttab code with gfn == mfn.
+     */
+    BUG_ON(!is_domain_direct_mapped(d));
+    BUG_ON(mfn != gfn);
+
+    /* We only support readable and writable flags */
+    if ( !(flags & (IOMMUF_readable | IOMMUF_writable)) )
+        return -EINVAL;
+
+    return arch_grant_map_page_identity(d, mfn, flags & IOMMUF_writable);
+}
+
+static int arm_smmu_unmap_page(struct domain *d, unsigned long gfn)
+{
+    /* This function should only be used by gnttab code when the domain
+     * is direct mapped
+     */
+    if ( !is_domain_direct_mapped(d) )
+        return -EINVAL;
+
+    return arch_grant_unmap_page_identity(d, gfn);
+}
+
 static const struct iommu_ops arm_smmu_iommu_ops = {
     .init = arm_smmu_iommu_domain_init,
     .hwdom_init = arm_smmu_iommu_hwdom_init,
@@ -1544,6 +1575,8 @@ static const struct iommu_ops arm_smmu_iommu_ops = {
     .iotlb_flush_all = arm_smmu_iotlb_flush_all,
     .assign_dt_device = arm_smmu_attach_dev,
     .reassign_dt_device = arm_smmu_reassign_dt_dev,
+    .map_page = arm_smmu_map_page,
+    .unmap_page = arm_smmu_unmap_page,
 };
 
 static int __init smmu_init(struct dt_device_node *dev,
diff --git a/xen/include/asm-arm/grant_table.h 
b/xen/include/asm-arm/grant_table.h
index e798880..0edad67 100644
--- a/xen/include/asm-arm/grant_table.h
+++ b/xen/include/asm-arm/grant_table.h
@@ -33,7 +33,8 @@ static inline int replace_grant_supported(void)
     ( ((i >= nr_grant_frames(d->grant_table)) &&                         \
      (i < max_grant_frames)) ? 0 : (d->arch.grant_table_gpfn[i]))
 
-#define gnttab_need_iommu_mapping(d)           (is_domain_direct_mapped(d))
+#define gnttab_need_iommu_mapping(d)                    \
+    (is_domain_direct_mapped(d) && need_iommu(d))
 
 #endif /* __ASM_GRANT_TABLE_H__ */
 /*
diff --git a/xen/include/public/features.h b/xen/include/public/features.h
index b7bf83f..16d92aa 100644
--- a/xen/include/public/features.h
+++ b/xen/include/public/features.h
@@ -94,8 +94,10 @@
 /* operation as Dom0 is supported */
 #define XENFEAT_dom0                      11
 
-/* Xen also maps grant references at pfn = mfn */
+/* Xen also maps grant references at pfn = mfn.
+ * This feature flag is deprecated and should not be used.
 #define XENFEAT_grant_map_identity        12
+ */
 
 #define XENFEAT_NR_SUBMAPS 1
 
-- 
1.7.10.4


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