xen/grant-table: pre-populate kernel unmap ops for xen_gnttab_unmap_refs()

When unmapping grants, instead of converting the kernel map ops to
unmap ops on the fly, pre-populate the set of unmap ops.

This allows the grant unmap for the kernel mappings to be trivially
batched in the future.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

7 files changed, 30 insertions, 23 deletions

diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
index 68c739b3fdf4..2f7e6ff67d51 100644
--- a/arch/arm/include/asm/xen/page.h
+++ b/arch/arm/include/asm/xen/page.h
@@ -92,7 +92,7 @@ extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
                                    struct page **pages, unsigned int count);
 
 extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-                                     struct gnttab_map_grant_ref *kmap_ops,
+                                     struct gnttab_unmap_grant_ref *kunmap_ops,
                                      struct page **pages, unsigned int count);
 
 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
index 054857776254..cb7a14c5cd69 100644
--- a/arch/arm/xen/p2m.c
+++ b/arch/arm/xen/p2m.c
@@ -102,7 +102,7 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 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 gnttab_unmap_grant_ref *kunmap_ops,
                               struct page **pages, unsigned int count)
 {
         int i;
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 5eea09915a15..e9f52fe2d56a 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -55,7 +55,7 @@ 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 clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-                                     struct gnttab_map_grant_ref *kmap_ops,
+                                     struct gnttab_unmap_grant_ref *kunmap_ops,
                                      struct page **pages, unsigned int count);
 extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
 
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 70fb5075c901..df40b2888eae 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -816,7 +816,7 @@ static struct page *m2p_find_override(unsigned long mfn)
 }
 
 static int m2p_remove_override(struct page *page,
-                               struct gnttab_map_grant_ref *kmap_op,
+                               struct gnttab_unmap_grant_ref *kunmap_op,
                                unsigned long mfn)
 {
         unsigned long flags;
@@ -840,7 +840,7 @@ static int m2p_remove_override(struct page *page,
         list_del(&page->lru);
         spin_unlock_irqrestore(&m2p_override_lock, flags);
 
-        if (kmap_op != NULL) {
+        if (kunmap_op != NULL) {
                 if (!PageHighMem(page)) {
                         struct multicall_space mcs;
                         struct gnttab_unmap_and_replace *unmap_op;
@@ -855,13 +855,13 @@ static int m2p_remove_override(struct page *page,
                          * issued. In this case handle is going to -1 because
                          * it hasn't been modified yet.
                          */
-                        if (kmap_op->handle == -1)
+                        if (kunmap_op->handle == -1)
                                 xen_mc_flush();
                         /*
                          * Now if kmap_op->handle is negative it means that the
                          * hypercall actually returned an error.
                          */
-                        if (kmap_op->handle == GNTST_general_error) {
+                        if (kunmap_op->handle == GNTST_general_error) {
                                 pr_warn("m2p_remove_override: pfn %lx mfn %lx, failed to modify kernel mappings",
                                         pfn, mfn);
                                 put_balloon_scratch_page();
@@ -873,9 +873,9 @@ static int m2p_remove_override(struct page *page,
                         mcs = __xen_mc_entry(
                                 sizeof(struct gnttab_unmap_and_replace));
                         unmap_op = mcs.args;
-                        unmap_op->host_addr = kmap_op->host_addr;
+                        unmap_op->host_addr = kunmap_op->host_addr;
                         unmap_op->new_addr = scratch_page_address;
-                        unmap_op->handle = kmap_op->handle;
+                        unmap_op->handle = kunmap_op->handle;
 
                         MULTI_grant_table_op(mcs.mc,
                                 GNTTABOP_unmap_and_replace, unmap_op, 1);
@@ -887,7 +887,6 @@ static int m2p_remove_override(struct page *page,
 
                         xen_mc_issue(PARAVIRT_LAZY_MMU);
 
-                        kmap_op->host_addr = 0;
                         put_balloon_scratch_page();
                 }
         }
@@ -912,7 +911,7 @@ static int m2p_remove_override(struct page *page,
 }
 
 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-                              struct gnttab_map_grant_ref *kmap_ops,
+                              struct gnttab_unmap_grant_ref *kunmap_ops,
                               struct page **pages, unsigned int count)
 {
         int i, ret = 0;
@@ -921,7 +920,7 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
         if (xen_feature(XENFEAT_auto_translated_physmap))
                 return 0;
 
-        if (kmap_ops &&
+        if (kunmap_ops &&
             !in_interrupt() &&
             paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
                 arch_enter_lazy_mmu_mode();
@@ -942,8 +941,8 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
                 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 (kunmap_ops)
+                        ret = m2p_remove_override(pages[i], &kunmap_ops[i], mfn);
                 if (ret)
                         goto out;
         }
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 073b4a19a8b0..6444172f2842 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -91,6 +91,7 @@ struct grant_map {
         struct gnttab_map_grant_ref   *map_ops;
         struct gnttab_unmap_grant_ref *unmap_ops;
         struct gnttab_map_grant_ref   *kmap_ops;
+        struct gnttab_unmap_grant_ref *kunmap_ops;
         struct page **pages;
 };
 
@@ -124,6 +125,7 @@ static void gntdev_free_map(struct grant_map *map)
         kfree(map->map_ops);
         kfree(map->unmap_ops);
         kfree(map->kmap_ops);
+        kfree(map->kunmap_ops);
         kfree(map);
 }
 
@@ -140,11 +142,13 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
         add->map_ops   = kcalloc(count, sizeof(add->map_ops[0]), GFP_KERNEL);
         add->unmap_ops = kcalloc(count, sizeof(add->unmap_ops[0]), GFP_KERNEL);
         add->kmap_ops  = kcalloc(count, sizeof(add->kmap_ops[0]), GFP_KERNEL);
+        add->kunmap_ops = kcalloc(count, sizeof(add->kunmap_ops[0]), GFP_KERNEL);
         add->pages     = kcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);
         if (NULL == add->grants    ||
             NULL == add->map_ops   ||
             NULL == add->unmap_ops ||
             NULL == add->kmap_ops  ||
+            NULL == add->kunmap_ops ||
             NULL == add->pages)
                 goto err;
 
@@ -155,6 +159,7 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
                 add->map_ops[i].handle = -1;
                 add->unmap_ops[i].handle = -1;
                 add->kmap_ops[i].handle = -1;
+                add->kunmap_ops[i].handle = -1;
         }
 
         add->index = 0;
@@ -280,6 +285,8 @@ static int map_grant_pages(struct grant_map *map)
                                 map->flags | GNTMAP_host_map,
                                 map->grants[i].ref,
                                 map->grants[i].domid);
+                        gnttab_set_unmap_op(&map->kunmap_ops[i], address,
+                                map->flags | GNTMAP_host_map, -1);
                 }
         }
 
@@ -290,13 +297,14 @@ static int map_grant_pages(struct grant_map *map)
                 return err;
 
         for (i = 0; i < map->count; i++) {
-                if (map->map_ops[i].status)
+                if (map->map_ops[i].status) {
                         err = -EINVAL;
-                else {
-                        BUG_ON(map->map_ops[i].handle == -1);
-                        map->unmap_ops[i].handle = map->map_ops[i].handle;
-                        pr_debug("map handle=%d\n", map->map_ops[i].handle);
+                        continue;
                 }
+
+                map->unmap_ops[i].handle = map->map_ops[i].handle;
+                if (use_ptemod)
+                        map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
         }
         return err;
 }
@@ -316,7 +324,7 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
         }
 
         err = gnttab_unmap_refs(map->unmap_ops + offset,
-                        use_ptemod ? map->kmap_ops + offset : NULL, map->pages + offset,
+                        use_ptemod ? map->kunmap_ops + offset : NULL, map->pages + offset,
                         pages);
         if (err)
                 return err;
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 7786291ba229..999d7abdbcec 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -738,7 +738,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 EXPORT_SYMBOL_GPL(gnttab_map_refs);
 
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-                      struct gnttab_map_grant_ref *kmap_ops,
+                      struct gnttab_unmap_grant_ref *kunmap_ops,
                       struct page **pages, unsigned int count)
 {
         int ret;
@@ -747,7 +747,7 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
         if (ret)
                 return ret;
 
-        return clear_foreign_p2m_mapping(unmap_ops, kmap_ops, pages, count);
+        return clear_foreign_p2m_mapping(unmap_ops, kunmap_ops, pages, count);
 }
 EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
 
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 3387465b9caa..7235d8f35459 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -167,7 +167,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
                     struct gnttab_map_grant_ref *kmap_ops,
                     struct page **pages, unsigned int count);
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-                      struct gnttab_map_grant_ref *kunmap_ops,
+                      struct gnttab_unmap_grant_ref *kunmap_ops,
                       struct page **pages, unsigned int count);
 
 /* Perform a batch of grant map/copy operations. Retry every batch slot