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Re: [Xen-devel] [v3][PATCH 1/1] xen:vtd: missing RMRR mapping while share EPT



On 2014/7/24 19:11, Tim Deegan wrote:
At 19:00 +0800 on 24 Jul (1406224818), Tiejun Chen wrote:
intel_iommu_map_page() does nothing if VT-d shares EPT page table.
So rmrr_identity_mapping() never create RMRR mapping but in some
cases like some GFX drivers it still need to access RMRR.

Here we will create those RMRR mappings even in shared EPT case.

Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>

For the interaction with p2m code:

Acked-by: Tim Deegn <tim@xxxxxxx>

Thanks a lot.


though I am still worried about what happens if this overwrites an
existing mapping.


As I understand RMRR should be specific. Its unlikely created for different mapping since this should be fixed in BIOS phase. And this is why that function is named as rmrr_identity_mapping().

Tiejun

Tim.

---
  xen/drivers/passthrough/vtd/iommu.c | 10 ++++++++--
  1 file changed, 8 insertions(+), 2 deletions(-)

v3:

* Use set_mmio_p2m_entry() to replace p2m_set_entry()
* Use ASSERT to check

v2:

* Fix coding style.
* Still need to abide intel_iommu_map_page(), so we should do nothing
   if dom0 and iommu supports pass thru.

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 042b882..f08a1fc 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1867,8 +1867,14 @@ static int rmrr_identity_mapping(struct domain *d,

      while ( base_pfn < end_pfn )
      {
-        if ( intel_iommu_map_page(d, base_pfn, base_pfn,
-                                  IOMMUF_readable|IOMMUF_writable) )
+        if ( iommu_use_hap_pt(d) )
+        {
+            ASSERT(!iommu_passthrough || !is_hardware_domain(d));
+            if ( set_mmio_p2m_entry(d, base_pfn, _mfn(base_pfn)) )
+                return -1;
+        }
+        else if ( intel_iommu_map_page(d, base_pfn, base_pfn,
+                                       IOMMUF_readable|IOMMUF_writable) )
              return -1;
          base_pfn++;
      }
--
1.9.1


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