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Re: [PATCH v5 2/2] xen/arm: allow translated iommu mappings



Hi,

On 25/07/2025 15:01, Stewart Hildebrand wrote:
From: Stefano Stabellini <stefano.stabellini@xxxxxxx>

In preparation of exposing vITS to domUs, generalize arm_iommu_map_page
and arm_iommu_unmap_page to allow ITS doorbell mappings with dfn != mfn.

The mfn does not need to be passed to guest_physmap_remove_page since
there is no mfn checking on the p2m_iommu_map_{rw,ro} p2m types during
unmap. Pass INVALID_MFN to guest_physmap_remove_page.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>

Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

---
v4->v5:
* no change

v3->v4:
* no change

v2->v3:
* split change from ("xen/arm: fix arm_iommu_map_page after f9f6b22ab")
* both map and unmap
---
  xen/drivers/passthrough/arm/iommu_helpers.c | 11 ++---------
  1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/xen/drivers/passthrough/arm/iommu_helpers.c 
b/xen/drivers/passthrough/arm/iommu_helpers.c
index bdb271584b0d..a3e3cafb8705 100644
--- a/xen/drivers/passthrough/arm/iommu_helpers.c
+++ b/xen/drivers/passthrough/arm/iommu_helpers.c
@@ -36,9 +36,6 @@ int __must_check arm_iommu_map_page(struct domain *d, dfn_t 
dfn, mfn_t mfn,
  {
      p2m_type_t t;
- BUG_ON(!domain_use_host_layout(d));
-    BUG_ON(mfn_x(mfn) != dfn_x(dfn));
-
      /* We only support readable and writable flags */
      if ( !(flags & (IOMMUF_readable | IOMMUF_writable)) )
          return -EINVAL;
@@ -49,7 +46,7 @@ int __must_check arm_iommu_map_page(struct domain *d, dfn_t 
dfn, mfn_t mfn,
       * The function guest_physmap_add_entry replaces the current mapping
       * if there is already one...
       */
-    return guest_physmap_add_entry(d, _gfn(dfn_x(dfn)), _mfn(dfn_x(dfn)),
+    return guest_physmap_add_entry(d, _gfn(dfn_x(dfn)), mfn,
                                     IOMMUF_order(flags), t);
  }
@@ -58,11 +55,7 @@ int __must_check arm_iommu_unmap_page(struct domain *d, dfn_t dfn,
                                        unsigned int order,
                                        unsigned int *flush_flags)
  {
-    if ( !domain_use_host_layout(d) )
-        return -EINVAL;
-
-    return guest_physmap_remove_page(d, _gfn(dfn_x(dfn)), _mfn(dfn_x(dfn)),
-                                     order);
+    return guest_physmap_remove_page(d, _gfn(dfn_x(dfn)), INVALID_MFN, order);
  }
/*

--
Julien Grall




 


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