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



On 2014/7/24 17:41, Jan Beulich wrote:
On 24.07.14 at 10:28, <tiejun.chen@xxxxxxxxx> wrote:
On 2014/7/24 15:45, Jan Beulich wrote:
On 24.07.14 at 09:00, <tiejun.chen@xxxxxxxxx> wrote:
On 2014/7/24 14:14, Jan Beulich wrote:
On 24.07.14 at 03:23, <tiejun.chen@xxxxxxxxx> wrote:
@@ -1867,7 +1869,21 @@ static int rmrr_identity_mapping(struct domain *d,

         while ( base_pfn < end_pfn )
         {
-        if ( intel_iommu_map_page(d, base_pfn, base_pfn,
+        if ( iommu_use_hap_pt(d) )

Don't you, btw, need to extend this condition by
&& (!iommu_passthrough || !is_hardware_domain(d))?

Why do we need these checks here?

At least for documentation purposes: It would be wrong to try to
establish these mappings. I reckon iommu_use_hap_pt() implies the
combined other condition, so an ASSERT() would presumably be fine
as well (and get even closer to the intended documentation purpose).


I think if() should be reasonable here. Because

intel_iommu_map_page()
{
        ...
      /* do nothing if dom0 and iommu supports pass thru */
      if ( iommu_passthrough && is_hardware_domain(d) )
          return 0;

We just do nothing to return simply. But if ASSERT will cause abort.

Then tell me the scenario where iommu_use_hap_pt(d) is true and
both iommu_passthrough and is_hardware_domain(d) are true too.

Then HVM?

Anyway I did a test like this,

        if (iommu_use_hap_pt(d))
        {
                ASSERT (iommu_passthrough && is_hardware_domain(d));

Then Xen really reboot.

Thanks
Tiejun

Remember that for Dom0 iommu_use_hap_pt() can be true only for
PVH, and PVH implies !iommu_passthrough.

Jan




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