xen: define BIOVEC_PHYS_MERGEABLE()

Impact: allow Xen control of bio merging When running in Xen domain with device access, we need to make sure the block subsystem doesn't merge requests across pages which aren't machine physically contiguous. To do this, we define our own BIOVEC_PHYS_MERGEABLE. When CONFIG_XEN isn't enabled, or we're not running in a Xen domain, this has identical behaviour to the normal implementation. When running under Xen, we also make sure the underlying machine pages are the same or adjacent. Signed-off-by: Jeremy Fitzhardinge <[email protected]> Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
beagleboard · Oct 18, 2010 · d8e0420 · d8e0420
1 parent 23ace95
commit d8e0420
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Showing 3 changed files with 27 additions and 1 deletion.
diff --git 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
@@ -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
@@ -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));
+}