On Thu, 26 Jul 2012, Konrad Rzeszutek Wilk wrote:

On Thu, Jul 26, 2012 at 04:33:45PM +0100, Stefano Stabellini wrote:

quoted

ARM Xen guests always use paging in hardware, like PV on HVM guests in
the X86 world.

Nice, so no dealing with the P2M at all in the guest?

Nope ;-)

quoted

Signed-off-by: Stefano Stabellini <redacted>
---
 arch/arm/include/asm/xen/page.h |   77 +++++++++++++++++++++++++++++++++++++++
 1 files changed, 77 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/include/asm/xen/page.h

diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
new file mode 100644
index 0000000..6cfe9a1
--- /dev/null
+++ b/arch/arm/include/asm/xen/page.h

@@ -0,0 +1,77 @@
+#ifndef _ASM_ARM_XEN_PAGE_H
+#define _ASM_ARM_XEN_PAGE_H
+
+#include <asm/page.h>
+#include <linux/pfn.h>
+#include <linux/types.h>
+#include <asm/pgtable.h>
+#include <xen/interface/grant_table.h>

I don't if it makes such a difference, but putting the headers in sorted
order is sometimes nicer than just randomly.. But that might be just
me liking an orderly world nowadays :-)

I can do that

quoted

+
+#define pfn_to_mfn(pfn)			(pfn)
+#define phys_to_machine_mapping_valid	(1)
+#define mfn_to_pfn(mfn)			(mfn)
+#define mfn_to_virt(m)			(__va(mfn_to_pfn(m) << PAGE_SHIFT))
+
+#define pte_mfn	    pte_pfn
+#define mfn_pte	    pfn_pte
+
+/* Xen machine address */
+typedef struct xmaddr {
+	phys_addr_t maddr;
+} xmaddr_t;
+
+/* Xen pseudo-physical address */
+typedef struct xpaddr {
+	phys_addr_t paddr;
+} xpaddr_t;
+
+#define XMADDR(x)	((xmaddr_t) { .maddr = (x) })
+#define XPADDR(x)	((xpaddr_t) { .paddr = (x) })
+
+static inline xmaddr_t phys_to_machine(xpaddr_t phys)
+{
+	unsigned offset = phys.paddr & ~PAGE_MASK;
+	return XMADDR(PFN_PHYS(pfn_to_mfn(PFN_DOWN(phys.paddr))) | offset);
+}
+
+static inline xpaddr_t machine_to_phys(xmaddr_t machine)
+{
+	unsigned offset = machine.maddr & ~PAGE_MASK;
+	return XPADDR(PFN_PHYS(mfn_to_pfn(PFN_DOWN(machine.maddr))) | offset);
+}
+/* VIRT <-> MACHINE conversion */
+#define virt_to_machine(v)	(phys_to_machine(XPADDR(__pa(v))))
+#define virt_to_pfn(v)          (PFN_DOWN(__pa(v)))
+#define virt_to_mfn(v)		(pfn_to_mfn(virt_to_pfn(v)))
+#define mfn_to_virt(m)		(__va(mfn_to_pfn(m) << PAGE_SHIFT))
+
+static inline xmaddr_t arbitrary_virt_to_machine(void *vaddr)
+{
+	/* XXX: assuming it is mapped in the kernel 1:1 */
+	return virt_to_machine(vaddr);
+}
+
+/* XXX: this shouldn't be here */

So why is it here?

lookup_address shouldn't be here because it is an x86-only interface.
However both gntdev.c and xenbus_client.c call it (in PV only code paths
that are never taken in a PV on HVM guest), so in order to compile them
I have to define lookup_address.

quoted

+static inline pte_t *lookup_address(unsigned long address, unsigned int *level)
+{
+	BUG();
+	return NULL;
+}
+
+static inline int m2p_add_override(unsigned long mfn, struct page *page,
+		struct gnttab_map_grant_ref *kmap_op)
+{
+	return 0;
+}
+
+static inline int m2p_remove_override(struct page *page, bool clear_pte)
+{
+	return 0;
+}
+
+static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
+{
+	BUG();
+	return false;
+}
+#endif /* _ASM_ARM_XEN_PAGE_H */