[PATCH v2 01/20] xen: Add Xen specific page definition

[Julien Grall]

The Xen hypercall interface is always using 4K page granularity on ARM
and x86 architecture.

With the incoming support of 64K page granularity for ARM64 guest, it
won't be possible to re-use the Linux page definition in Xen drivers.

Introduce Xen page definition helpers based on the Linux page
definition. They have exactly the same name but prefixed with
XEN_/xen_ prefix.

Also modify page_to_pfn to use new Xen page definition.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
---
    I'm wondering if we should drop page_to_pfn has the macro will likely
    misuse when Linux is using 64KB page granularity.

    Changes in v2:
        - Add XEN_PFN_UP
        - Add a comment describing the behavior of page_to_pfn
---
 include/xen/page.h | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/include/xen/page.h b/include/xen/page.h
index c5ed20b..8ebd37b 100644
--- a/include/xen/page.h
+++ b/include/xen/page.h
@@ -1,11 +1,30 @@
 #ifndef _XEN_PAGE_H
 #define _XEN_PAGE_H
 
+#include <asm/page.h>
+
+/* The hypercall interface supports only 4KB page */
+#define XEN_PAGE_SHIFT	12
+#define XEN_PAGE_SIZE	(_AC(1,UL) << XEN_PAGE_SHIFT)
+#define XEN_PAGE_MASK	(~(XEN_PAGE_SIZE-1))
+#define xen_offset_in_page(p)	((unsigned long)(p) & ~XEN_PAGE_MASK)
+#define xen_pfn_to_page(pfn)	\
+	((pfn_to_page(((unsigned long)(pfn) << XEN_PAGE_SHIFT) >> PAGE_SHIFT)))
+#define xen_page_to_pfn(page)	\
+	(((page_to_pfn(page)) << PAGE_SHIFT) >> XEN_PAGE_SHIFT)
+
+#define XEN_PFN_PER_PAGE	(PAGE_SIZE / XEN_PAGE_SIZE)
+
+#define XEN_PFN_DOWN(x)	((x) >> XEN_PAGE_SHIFT)
+#define XEN_PFN_UP(x)	(((x) + XEN_PAGE_SIZE-1) >> XEN_PAGE_SHIFT)
+#define XEN_PFN_PHYS(x)	((phys_addr_t)(x) << XEN_PAGE_SHIFT)
+
 #include <asm/xen/page.h>
 
+/* Return the MFN associated to the first 4KB of the page */
 static inline unsigned long page_to_mfn(struct page *page)
 {
-	return pfn_to_mfn(page_to_pfn(page));
+	return pfn_to_mfn(xen_page_to_pfn(page));
 }
 
 struct xen_memory_region {
-- 
2.1.4

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