[xen staging] libxl: respect unset video_memkb for Dom0

[patchbot@xxxxxxx]

commit 35a68ba3b2ad888f4c302d4cf5de8ab42f64236e
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Sep 9 08:17:09 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Sep 9 08:17:09 2025 +0200

    libxl: respect unset video_memkb for Dom0
    
    Without this, Dom0 will have have a curiously off-by-1 target_memkb
    value displayed by "xl list -l".
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
    Acked-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 tools/libs/light/libxl_internal.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/libs/light/libxl_internal.h 
b/tools/libs/light/libxl_internal.h
index 4b6587a27a..062123eed4 100644
--- a/tools/libs/light/libxl_internal.h
+++ b/tools/libs/light/libxl_internal.h
@@ -4683,7 +4683,10 @@ uint64_t libxl__get_targetmem_fudge(libxl__gc *gc,
                                 info->max_memkb > info->target_memkb)
                                 ? LIBXL_MAXMEM_CONSTANT : 0;
 
-    return info->video_memkb + mem_target_fudge;
+    if (info->video_memkb != LIBXL_MEMKB_DEFAULT)
+        mem_target_fudge += info->video_memkb;
+
+    return mem_target_fudge;
 }
 
 int libxl__get_memory_target(libxl__gc *gc, uint32_t domid,
--
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