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>

5 files changed, 156 insertions, 96 deletions

diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
index e0965abacb7d..cf4f3e867395 100644
--- a/arch/arm/include/asm/xen/page.h
+++ b/arch/arm/include/asm/xen/page.h
@@ -97,16 +97,13 @@ static inline pte_t *lookup_address(unsigned long address, unsigned int *level)
         return NULL;
 }
 
-static inline int m2p_add_override(unsigned long mfn, struct page *page,
-                struct gnttab_map_grant_ref *kmap_op)
-{
-        return 0;
-}
+extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
+                                   struct gnttab_map_grant_ref *kmap_ops,
+                                   struct page **pages, unsigned int count);
 
-static inline int m2p_remove_override(struct page *page, bool clear_pte)
-{
-        return 0;
-}
+extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
+                                     struct gnttab_map_grant_ref *kmap_ops,
+                                     struct page **pages, unsigned int count);
 
 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 bool __set_phys_to_machine_multi(unsigned long pfn, unsigned long mfn,
diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
index b31ee1b275b0..97baf4427817 100644
--- a/arch/arm/xen/p2m.c
+++ b/arch/arm/xen/p2m.c
@@ -146,6 +146,38 @@ unsigned long __mfn_to_pfn(unsigned long mfn)
 }
 EXPORT_SYMBOL_GPL(__mfn_to_pfn);
 
+int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
+                            struct gnttab_map_grant_ref *kmap_ops,
+                            struct page **pages, unsigned int count)
+{
+        int i;
+
+        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 0;
+}
+EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
+
+int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
+                              struct gnttab_map_grant_ref *kmap_ops,
+                              struct page **pages, unsigned int count)
+{
+        int i;
+
+        for (i = 0; i < count; i++) {
+                set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
+                                    INVALID_P2M_ENTRY);
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
+
 bool __set_phys_to_machine_multi(unsigned long pfn,
                 unsigned long mfn, unsigned long nr_pages)
 {
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 3e276eb23d1b..c949923a5668 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -49,10 +49,17 @@ extern bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 extern unsigned long set_phys_range_identity(unsigned long pfn_s,
                                              unsigned long pfn_e);
 
+extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
+                                   struct gnttab_map_grant_ref *kmap_ops,
+                                   struct page **pages, unsigned int count);
 extern int m2p_add_override(unsigned long mfn, struct page *page,
                             struct gnttab_map_grant_ref *kmap_op);
+extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
+                                     struct gnttab_map_grant_ref *kmap_ops,
+                                     struct page **pages, unsigned int count);
 extern int m2p_remove_override(struct page *page,
-                                struct gnttab_map_grant_ref *kmap_op);
+                               struct gnttab_map_grant_ref *kmap_op,
+                               unsigned long mfn);
 extern struct page *m2p_find_override(unsigned long mfn);
 extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
 
@@ -121,7 +128,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
                 pfn = m2p_find_override_pfn(mfn, ~0);
         }
 
-        /* 
+        /*
          * pfn is ~0 if there are no entries in the m2p for mfn or if the
          * entry doesn't map back to the mfn and m2p_override doesn't have a
          * valid entry for it.
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 696c694986d0..85e5d78c9874 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -881,6 +881,65 @@ static unsigned long mfn_hash(unsigned long mfn)
         return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
 }
 
+int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
+                            struct gnttab_map_grant_ref *kmap_ops,
+                            struct page **pages, unsigned int count)
+{
+        int i, ret = 0;
+        bool lazy = false;
+        pte_t *pte;
+
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+                return 0;
+
+        if (kmap_ops &&
+            !in_interrupt() &&
+            paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
+                arch_enter_lazy_mmu_mode();
+                lazy = true;
+        }
+
+        for (i = 0; i < count; i++) {
+                unsigned long mfn, pfn;
+
+                /* 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);
+                }
+                pfn = page_to_pfn(pages[i]);
+
+                WARN_ON(PagePrivate(pages[i]));
+                SetPagePrivate(pages[i]);
+                set_page_private(pages[i], mfn);
+                pages[i]->index = pfn_to_mfn(pfn);
+
+                if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
+                        ret = -ENOMEM;
+                        goto out;
+                }
+
+                if (kmap_ops) {
+                        ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
+                        if (ret)
+                                goto out;
+                }
+        }
+
+out:
+        if (lazy)
+                arch_leave_lazy_mmu_mode();
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
+
 /* Add an MFN override for a particular page */
 int m2p_add_override(unsigned long mfn, struct page *page,
                 struct gnttab_map_grant_ref *kmap_op)
@@ -899,13 +958,6 @@ int m2p_add_override(unsigned long mfn, struct page *page,
                                         "m2p_add_override: pfn %lx not mapped", pfn))
                         return -EINVAL;
         }
-        WARN_ON(PagePrivate(page));
-        SetPagePrivate(page);
-        set_page_private(page, mfn);
-        page->index = pfn_to_mfn(pfn);
-
-        if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
-                return -ENOMEM;
 
         if (kmap_op != NULL) {
                 if (!PageHighMem(page)) {
@@ -943,20 +995,62 @@ int m2p_add_override(unsigned long mfn, struct page *page,
         return 0;
 }
 EXPORT_SYMBOL_GPL(m2p_add_override);
+
+int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
+                              struct gnttab_map_grant_ref *kmap_ops,
+                              struct page **pages, unsigned int count)
+{
+        int i, ret = 0;
+        bool lazy = false;
+
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+                return 0;
+
+        if (kmap_ops &&
+            !in_interrupt() &&
+            paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
+                arch_enter_lazy_mmu_mode();
+                lazy = true;
+        }
+
+        for (i = 0; i < count; i++) {
+                unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
+                unsigned long pfn = page_to_pfn(pages[i]);
+
+                if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
+                        ret = -EINVAL;
+                        goto out;
+                }
+
+                set_page_private(pages[i], INVALID_P2M_ENTRY);
+                WARN_ON(!PagePrivate(pages[i]));
+                ClearPagePrivate(pages[i]);
+                set_phys_to_machine(pfn, pages[i]->index);
+
+                if (kmap_ops)
+                        ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
+                if (ret)
+                        goto out;
+        }
+
+out:
+        if (lazy)
+                arch_leave_lazy_mmu_mode();
+        return ret;
+}
+EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
+
 int m2p_remove_override(struct page *page,
-                struct gnttab_map_grant_ref *kmap_op)
+                        struct gnttab_map_grant_ref *kmap_op,
+                        unsigned long mfn)
 {
         unsigned long flags;
-        unsigned long mfn;
         unsigned long pfn;
         unsigned long uninitialized_var(address);
         unsigned level;
         pte_t *ptep = NULL;
 
         pfn = page_to_pfn(page);
-        mfn = get_phys_to_machine(pfn);
-        if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT))
-                return -EINVAL;
 
         if (!PageHighMem(page)) {
                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
@@ -970,10 +1064,7 @@ int m2p_remove_override(struct page *page,
         spin_lock_irqsave(&m2p_override_lock, flags);
         list_del(&page->lru);
         spin_unlock_irqrestore(&m2p_override_lock, flags);
-        WARN_ON(!PagePrivate(page));
-        ClearPagePrivate(page);
 
-        set_phys_to_machine(pfn, page->index);
         if (kmap_op != NULL) {
                 if (!PageHighMem(page)) {
                         struct multicall_space mcs;
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);