[Xen-devel] Vmap allocator fails to allocate beyond 128MB

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

Hi,

  When devices like SMMU request large ioremap space and if the total allocation
of vmap space is beyond 128MB the allocation fails for next requests
and following warning is seen

create_xen_entries: trying to replace an existing mapping
addr=40001000 mfn=fffd6

I found that vm_top is allocated with only 1 page which can hold
bitmap for only 128MB
space though 1GB of vmap space is assigned.

With 1GB vmap space following are the calculations

vm_base = 0x4000000
vm_end = 0x3ffff
vm_low = 0x8
nr = 1
vm_top = 0x8000

With the below patch, I could get allocations beyond 128MB.

where nr = 8 for 1GB vmap space

diff --git a/xen/common/vmap.c b/xen/common/vmap.c
index 783cea3..369212d 100644
--- a/xen/common/vmap.c
+++ b/xen/common/vmap.c
@@ -27,7 +27,7 @@ void __init vm_init(void)
     vm_base = (void *)VMAP_VIRT_START;
     vm_end = PFN_DOWN(arch_vmap_virt_end() - vm_base);
     vm_low = PFN_UP((vm_end + 7) / 8);
-    nr = PFN_UP((vm_low + 7) / 8);
+    nr = PFN_UP((vm_end + 7) / 8);
     vm_top = nr * PAGE_SIZE * 8;

     for ( i = 0, va = (unsigned long)vm_bitmap; i < nr; ++i, va += PAGE_SIZE )

Regards
Vijay

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