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Re: [Xen-devel] [PATCH v2] CONFIG_XEN_PV breaks xen_create_contiguous_region on ARM

Hi Stefano,

On 10/26/18 7:04 PM, Stefano Stabellini wrote:
From: Stefano Stabellini <stefanos@xxxxxxxxxx>

xen_create_contiguous_region has now only an implementation if
CONFIG_XEN_PV is defined. However, on ARM we never set CONFIG_XEN_PV but
we do have an implementation of xen_create_contiguous_region which is
required for swiotlb-xen to work correctly (although it just sets

Add a stub implementation of xen_remap_pfn: it should never be called on
ARM but it is necessary for linking.

This fixes a bug introduced by 16624390816c4c40df3d777b34665d3fd01e693d.

Again, this should contain a tag "Fixes: sha1 ("commit title")" so it can be picked for backporting automatically.

Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
CC: Jeff.Kubascik@xxxxxxxxxxxxxxx
CC: Jarvis.Roach@xxxxxxxxxxxxxxx
CC: Nathan.Studer@xxxxxxxxxxxxxxx
CC: vkuznets@xxxxxxxxxx
CC: boris.ostrovsky@xxxxxxxxxx
CC: jgross@xxxxxxxx
  arch/arm/xen/mm.c     | 8 ++++++++
  include/xen/xen-ops.h | 2 +-
  2 files changed, 9 insertions(+), 1 deletion(-)
Changes in v2:
- improve commit message
- add xen_remap_pfn stub implementation
- use if defined()
diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index 785d2a5..7230e22 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -182,6 +182,14 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, 
unsigned int order)
+int xen_remap_pfn(struct vm_area_struct *vma, unsigned long addr,
+                 xen_pfn_t *pfn, int nr, int *err_ptr, pgprot_t prot,
+                 unsigned int domid, bool no_translate, struct page **pages)
+       return -EOPNOTSUPP;

This does not match the "unimplemented" version in xen-ops.h.

But I find this solution quite ugly. Why don't you split the #ifdef in two below?

  const struct dma_map_ops *xen_dma_ops;
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index 18803ff..765dd05 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -42,7 +42,7 @@ int xen_setup_shutdown_event(void);
extern unsigned long *xen_contiguous_bitmap; -#ifdef CONFIG_XEN_PV
+#if defined(CONFIG_XEN_PV) || defined(CONFIG_ARM) || defined(CONFIG_ARM64)
  int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
                                unsigned int address_bits,
                                dma_addr_t *dma_handle);


Julien Grall

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