x86/vtd: relax EPT page table sharing check

The EPT page tables can be shared with the IOMMU as long as the page
sizes supported by EPT are also supported by the IOMMU.

Current code checks that both the IOMMU and EPT support the same page
sizes, but this is not strictly required, the IOMMU supporting more
page sizes than EPT is fine and shouldn't block page table sharing.

This is likely not a common case (IOMMU supporting more page sizes
than EPT), but should still be fixed for correctness.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>

diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index 07d40b37febc2cb9a4fffb99b5cbe4aad83b0d17..208b33c0e4703d568482d14eeca98c45c1ee7904 100644 (file)
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1914,8 +1914,8 @@ static int __init vtd_ept_page_compatible(struct vtd_iommu *iommu)
     if ( rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, ept_cap) != 0 ) 
         return 0;
 
-    return (ept_has_2mb(ept_cap) && opt_hap_2mb) == cap_sps_2mb(vtd_cap) &&
-           (ept_has_1gb(ept_cap) && opt_hap_1gb) == cap_sps_1gb(vtd_cap);
+    return (ept_has_2mb(ept_cap) && opt_hap_2mb) <= cap_sps_2mb(vtd_cap) &&
+           (ept_has_1gb(ept_cap) && opt_hap_1gb) <= cap_sps_1gb(vtd_cap);
 }
 
 /*