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Re: [Xen-devel] [v6][PATCH 2/2] xen:vtd: missing RMRR mapping while share EPT

On 2014/7/30 16:36, Jan Beulich wrote:
On 30.07.14 at 03:36, <tiejun.chen@xxxxxxxxx> wrote:
--- 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_identity_p2m_entry(d, base_pfn) )
+                return -1;
+        }
+        else if ( intel_iommu_map_page(d, base_pfn, base_pfn,
+                                       IOMMUF_readable|IOMMUF_writable) )
              return -1;

So I wonder how this plays together with

     /* FIXME: Because USB RMRR conflicts with guest bios region,
      * ignore USB RMRR temporarily.
     seg = pdev->seg;
     bus = pdev->bus;
     if ( is_usb_device(seg, bus, pdev->devfn) )
         ret = 0;
         goto done;

later in the same file (in intel_iommu_assign_device()). I.e. the
improvement you claim won't be achieved for passed through USB

I think we can remove this chunk of codes since these two patches already check if they conflicts.

devices afaict. One more aspect supporting my view that this
needs fully addressing rather than any such partial solution.

If we're talking about fixing all RMRR issues completely, these patches should not be enough. But I think these patches shouldn't block that complete solution because they're just checking to make sure we can create those RMRR mapping if possible. I mean no matter if we address more on RMRR, we still need these two patches to double-check/create RMRR mapping in shared EPT case, even we will reserve those ranges in guest as some guys recommended previously.


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