xen/grant-table: Refactor gnttab_[un]map_refs to avoid m2p_override

The grant mapping API does m2p_override unnecessarily: only gntdev needs it,
for blkback and future netback patches it just cause a lock contention, as
those pages never go to userspace. Therefore this series does the following:
- the bulk of the original function (everything after the mapping hypercall)
  is moved to arch-dependent set/clear_foreign_p2m_mapping
- the "if (xen_feature(XENFEAT_auto_translated_physmap))" branch goes to ARM
- therefore the ARM function could be much smaller, the m2p_override stubs
  could be also removed
- on x86 the set_phys_to_machine calls were moved up to this new funcion
  from m2p_override functions
- and m2p_override functions are only called when there is a kmap_ops param

It also removes a stray space from arch/x86/include/asm/xen/page.h.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Suggested-by: Anthony Liguori <aliguori@amazon.com>
Suggested-by: David Vrabel <david.vrabel@citrix.com>
Suggested-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

1 files changed, 3 insertions, 70 deletions

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index b84e3ab839aa..6d325bda76da 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -933,9 +933,6 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 		    struct page **pages, unsigned int count)
 {
 	int i, ret;
-	bool lazy = false;
-	pte_t *pte;
-	unsigned long mfn;
 
 	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);
 	if (ret)
@@ -947,45 +944,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
 						&map_ops[i].status, __func__);
 
-	/* this is basically a nop on x86 */
-	if (xen_feature(XENFEAT_auto_translated_physmap)) {
-		for (i = 0; i < count; i++) {
-			if (map_ops[i].status)
-				continue;
-			set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,
-					map_ops[i].dev_bus_addr >> PAGE_SHIFT);
-		}
-		return ret;
-	}
-
-	if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
-		arch_enter_lazy_mmu_mode();
-		lazy = true;
-	}
-
-	for (i = 0; i < count; i++) {
-		/* Do not add to override if the map failed. */
-		if (map_ops[i].status)
-			continue;
-
-		if (map_ops[i].flags & GNTMAP_contains_pte) {
-			pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
-				(map_ops[i].host_addr & ~PAGE_MASK));
-			mfn = pte_mfn(*pte);
-		} else {
-			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
-		}
-		ret = m2p_add_override(mfn, pages[i], kmap_ops ?
-				       &kmap_ops[i] : NULL);
-		if (ret)
-			goto out;
-	}
-
- out:
-	if (lazy)
-		arch_leave_lazy_mmu_mode();
-
-	return ret;
+	return set_foreign_p2m_mapping(map_ops, kmap_ops, pages, count);
 }
 EXPORT_SYMBOL_GPL(gnttab_map_refs);
 
@@ -993,39 +952,13 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
 		      struct gnttab_map_grant_ref *kmap_ops,
 		      struct page **pages, unsigned int count)
 {
-	int i, ret;
-	bool lazy = false;
+	int ret;
 
 	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);
 	if (ret)
 		return ret;
 
-	/* this is basically a nop on x86 */
-	if (xen_feature(XENFEAT_auto_translated_physmap)) {
-		for (i = 0; i < count; i++) {
-			set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
-					INVALID_P2M_ENTRY);
-		}
-		return ret;
-	}
-
-	if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
-		arch_enter_lazy_mmu_mode();
-		lazy = true;
-	}
-
-	for (i = 0; i < count; i++) {
-		ret = m2p_remove_override(pages[i], kmap_ops ?
-				       &kmap_ops[i] : NULL);
-		if (ret)
-			goto out;
-	}
-
- out:
-	if (lazy)
-		arch_leave_lazy_mmu_mode();
-
-	return ret;
+	return clear_foreign_p2m_mapping(unmap_ops, kmap_ops, pages, count);
 }
 EXPORT_SYMBOL_GPL(gnttab_unmap_refs);