[xen stable-4.15] VT-d: correct off-by-1 in number-of-IOMMUs check

[patchbot@xxxxxxx]

commit b9b3082002cac68726fb303e0abd2ff0113d4657
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Mar 23 17:01:30 2021 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Mar 23 17:01:30 2021 +0100

    VT-d: correct off-by-1 in number-of-IOMMUs check
    
    Otherwise, if we really run on a system with this many IOMMUs,
    entering/leaving S3 would overrun iommu_state[].
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
---
 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 9b58d566c8..44e407d19f 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1168,10 +1168,10 @@ int __init iommu_alloc(struct acpi_drhd_unit *drhd)
     unsigned long sagaw, nr_dom;
     int agaw;
 
-    if ( nr_iommus > MAX_IOMMUS )
+    if ( nr_iommus >= MAX_IOMMUS )
     {
         dprintk(XENLOG_ERR VTDPREFIX,
-                 "IOMMU: nr_iommus %d > MAX_IOMMUS\n", nr_iommus);
+                "IOMMU: nr_iommus %d > MAX_IOMMUS\n", nr_iommus + 1);
         return -ENOMEM;
     }
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.15