[xen staging] xen/arm: fix math in add_hwdom_free_regions

[patchbot@xxxxxxx]

commit 245e47cf8d292401b1147b9ceb0eedadec6288c7
Author:     Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
AuthorDate: Thu May 8 09:20:31 2025 -0400
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxx>
CommitDate: Thu May 8 16:36:55 2025 -0700

    xen/arm: fix math in add_hwdom_free_regions
    
    Erroneous logic was duplicated from add_ext_regions() into
    add_hwdom_free_regions(). Frame numbers are converted to addresses, but
    the end address (e) is rounded down to page size alignment. The logic to
    calculate the size assumes e points to the last address, not page,
    effectively leading to the region size being erroneously calculated to
    be 2M smaller than the actual size of the region.
    
    Fix by adding 1 to the frame number before converting back to address.
    
    Fixes: 02975cc38389 ("xen/arm: permit non direct-mapped Dom0 construction")
    Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
    Acked-by: Michal Orzel <michal.orzel@xxxxxxx>
---
 xen/common/device-tree/domain-build.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/common/device-tree/domain-build.c 
b/xen/common/device-tree/domain-build.c
index 762b63e2b0..9556af43e0 100644
--- a/xen/common/device-tree/domain-build.c
+++ b/xen/common/device-tree/domain-build.c
@@ -109,7 +109,7 @@ static int __init add_hwdom_free_regions(unsigned long 
s_gfn,
     struct membanks *free_regions = data;
     paddr_t start, size;
     paddr_t s = pfn_to_paddr(s_gfn);
-    paddr_t e = pfn_to_paddr(e_gfn);
+    paddr_t e = pfn_to_paddr(e_gfn + 1) - 1;
     unsigned int i, j;
 
     if ( free_regions->nr_banks >= free_regions->max_banks )
--
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