[xen stable-4.12] x86/vtd: relax EPT page table sharing check

[patchbot@xxxxxxx]

commit 55d65346d70b779f082b7764480e745cb51e675f
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Apr 27 15:53:26 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Apr 27 15:53:26 2020 +0200

    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@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    master commit: 3957e12c02670b97855ef0933b373f99993fa598
    master date: 2020-04-21 10:54:56 +0200
---
 xen/drivers/passthrough/vtd/iommu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 77ba8e14a6..ed50d34c91 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1957,8 +1957,8 @@ static int __init vtd_ept_page_compatible(struct 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);
 }
 
 /*
--
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