3 files changed, 27 insertions, 1 deletions

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 30a3e9776123..0ad29d401565 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -41,6 +41,8 @@
 #include <asm-generic/int-ll64.h>
 #include <asm/page.h>
 
+#include <xen/xen.h>
+
 #define build_mmio_read(name, size, type, reg, barrier) \
 static inline type name(const volatile void __iomem *addr) \
 { type ret; asm volatile("mov" size " %1,%0":reg (ret) \
@@ -349,6 +351,17 @@ extern void __iomem *early_memremap(resource_size_t phys_addr,
 extern void early_iounmap(void __iomem *addr, unsigned long size);
 extern void fixup_early_ioremap(void);
 
+#ifdef CONFIG_XEN
+struct bio_vec;
+
+extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
+                                      const struct bio_vec *vec2);
+
+#define BIOVEC_PHYS_MERGEABLE(vec1, vec2)                               \
+        (__BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&                         \
+         (!xen_domain() || xen_biovec_phys_mergeable(vec1, vec2)))
+#endif  /* CONFIG_XEN */
+
 #define IO_SPACE_LIMIT 0xffff
 
 #endif /* _ASM_X86_IO_H */
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index fcaf838f54be..b47f5da674d3 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -1,4 +1,4 @@
-obj-y   += grant-table.o features.o events.o manage.o
+obj-y   += grant-table.o features.o events.o manage.o biomerge.o
 obj-y   += xenbus/
 
 nostackp := $(call cc-option, -fno-stack-protector)
diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c
new file mode 100644
index 000000000000..ba6eda4b5143
--- /dev/null
+++ b/drivers/xen/biomerge.c
@@ -0,0 +1,13 @@
+#include <linux/bio.h>
+#include <linux/io.h>
+#include <xen/page.h>
+
+bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
+                               const struct bio_vec *vec2)
+{
+        unsigned long mfn1 = pfn_to_mfn(page_to_pfn(vec1->bv_page));
+        unsigned long mfn2 = pfn_to_mfn(page_to_pfn(vec2->bv_page));
+
+        return __BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&
+                ((mfn1 == mfn2) || ((mfn1+1) == mfn2));
+}