[xen master] xen/arm: Handle empty grant table region in find_unallocated_memory()

[patchbot@xxxxxxx]

commit 21ec0c42267be169be6019e5a09b61cbf16d10ce
Author:     Michal Orzel <michal.orzel@xxxxxxx>
AuthorDate: Thu Aug 24 11:06:40 2023 +0200
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Tue Sep 12 14:29:14 2023 +0100

    xen/arm: Handle empty grant table region in find_unallocated_memory()
    
    When creating dom0 with grant table support disabled in Xen and no IOMMU,
    the following assert is triggered (debug build):
    "Assertion 's <= e' failed at common/rangeset.c:189"
    
    (XEN) Xen call trace:
    (XEN)    [<0000020000218568>] rangeset_remove_range+0xbc/0x2cc (PC)
    (XEN)    [<00000200002c76bc>] 
domain_build.c#make_hypervisor_node+0x294/0x7c4 (LR)
    (XEN)    [<00000200002ca240>] domain_build.c#handle_node+0x7ec/0x924
    (XEN)    [<00000200002ca7ac>] domain_build.c#construct_dom0+0x434/0x4d8
    
    This is because find_unallocated_memory() (used to find memory holes
    for extended regions) calls rangeset_remove_range() for an empty
    grant table region. Fix it by checking if the size of region is not 0.
    
    Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/arch/arm/domain_build.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 29dcbb8a2e..6cf0450858 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1633,14 +1633,18 @@ static int __init find_unallocated_memory(const struct 
kernel_info *kinfo,
     }
 
     /* Remove grant table region */
-    start = kinfo->gnttab_start;
-    end = kinfo->gnttab_start + kinfo->gnttab_size;
-    res = rangeset_remove_range(unalloc_mem, PFN_DOWN(start), PFN_DOWN(end - 
1));
-    if ( res )
+    if ( kinfo->gnttab_size )
     {
-        printk(XENLOG_ERR "Failed to remove: %#"PRIpaddr"->%#"PRIpaddr"\n",
-               start, end);
-        goto out;
+        start = kinfo->gnttab_start;
+        end = kinfo->gnttab_start + kinfo->gnttab_size;
+        res = rangeset_remove_range(unalloc_mem, PFN_DOWN(start),
+                                    PFN_DOWN(end - 1));
+        if ( res )
+        {
+            printk(XENLOG_ERR "Failed to remove: %#"PRIpaddr"->%#"PRIpaddr"\n",
+                   start, end);
+            goto out;
+        }
     }
 
     start = 0;
--
generated by git-patchbot for /home/xen/git/xen.git#master