Re: [Xen-devel] [RFC PATCH] xen/arm: Vmap allocator fails to allocate beyond 128M

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.02.15 at 07:07, <vijay.kilari@xxxxxxxxx> wrote:
> In vmap_init, map_pages_to_xen() is called for mapping
> vm_bitmap. Initially one page of vm_bitmap is allocated
> and mapped using PAGE_HYPERVISOR attribute.
> For the rest of vm_bitmap pages, MAP_SMALL_PAGES attribute
> is used to map.
> 
> In ARM for both PAGE_HYPERVISOR and MAP_SMALL_PAGES, valid bit
> is set to 1 in pte entry for these mapping.
> 
> In vma_alloc(), map_pages_to_xen() is failing for >128MB because
> for this next vm_bitmap page the mapping is already set in vm_init()
> with valid bit set in pte entry. So map_pages_to_xen() in
> ARM returns error.
> 
> On x86, for the pages mapped with MAP_SMALL_PAGES attribute
> valid bit is not set. So the common vmap code assumes the
> same behaviour from arm. However this is not the case.
> 
> This patch will set valid bit to 0 in pte entry when
> pages are mapped with MAP_SMALL_PAGES.
> 
> Signed-off-by: Vijaya Kumar K<Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>

Yes, this is precisely the kind of change I expected to address
the previously described problem.

Jan


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