[PATCH v3 bpf-next 2/3] mm, xen: Separate xen use cases from ioremap.

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

From: Alexei Starovoitov <ast@kernel.org>

xen grant table and xenbus ring are not ioremap the way arch specific code
is using it, so let's add VM_XEN flag to separate these use cases from
VM_IOREMAP users. xen will not and should not be calling
ioremap_page_range() on that range. /proc/vmallocinfo will print such
regions as "xen" instead of "ioremap".

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 arch/x86/xen/grant-table.c         | 2 +-
 drivers/xen/xenbus/xenbus_client.c | 2 +-
 include/linux/vmalloc.h            | 1 +
 mm/vmalloc.c                       | 7 +++++--
 4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index 1e681bf62561..b816db0349c4 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -104,7 +104,7 @@ static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames)
 	area->ptes = kmalloc_array(nr_frames, sizeof(*area->ptes), GFP_KERNEL);
 	if (area->ptes == NULL)
 		return -ENOMEM;
-	area->area = get_vm_area(PAGE_SIZE * nr_frames, VM_IOREMAP);
+	area->area = get_vm_area(PAGE_SIZE * nr_frames, VM_XEN);
 	if (!area->area)
 		goto out_free_ptes;
 	if (apply_to_page_range(&init_mm, (unsigned long)area->area->addr,
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 32835b4b9bc5..b9c81a2d578b 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -758,7 +758,7 @@ static int xenbus_map_ring_pv(struct xenbus_device *dev,
 	bool leaked = false;
 	int err = -ENOMEM;
 
-	area = get_vm_area(XEN_PAGE_SIZE * nr_grefs, VM_IOREMAP);
+	area = get_vm_area(XEN_PAGE_SIZE * nr_grefs, VM_XEN);
 	if (!area)
 		return -ENOMEM;
 	if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index c720be70c8dd..71075ece0ed2 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -28,6 +28,7 @@ struct iov_iter;		/* in uio.h */
 #define VM_FLUSH_RESET_PERMS	0x00000100	/* reset direct map and flush TLB on unmap, can't be freed in atomic context */
 #define VM_MAP_PUT_PAGES	0x00000200	/* put pages and free array in vfree */
 #define VM_ALLOW_HUGE_VMAP	0x00000400      /* Allow for huge pages on archs with HAVE_ARCH_HUGE_VMALLOC */
+#define VM_XEN			0x00000800	/* xen grant table and xenbus use cases */
 
 #if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \
 	!defined(CONFIG_KASAN_VMALLOC)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index f42f98a127d5..d53ece3f38ee 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3822,9 +3822,9 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
 
 		if (flags & VMAP_RAM)
 			copied = vmap_ram_vread_iter(iter, addr, n, flags);
-		else if (!(vm && (vm->flags & VM_IOREMAP)))
+		else if (!(vm && (vm->flags & (VM_IOREMAP | VM_XEN))))
 			copied = aligned_vread_iter(iter, addr, n);
-		else /* IOREMAP area is treated as memory hole */
+		else /* IOREMAP | XEN area is treated as memory hole */
 			copied = zero_iter(iter, n);
 
 		addr += copied;
@@ -4415,6 +4415,9 @@ static int s_show(struct seq_file *m, void *p)
 	if (v->flags & VM_IOREMAP)
 		seq_puts(m, " ioremap");
 
+	if (v->flags & VM_XEN)
+		seq_puts(m, " xen");
+
 	if (v->flags & VM_ALLOC)
 		seq_puts(m, " vmalloc");
 
-- 
2.34.1