This ioctl allows the users of a shared page to be notified when
the other end exits abnormally.
Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
drivers/xen/gntalloc.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
drivers/xen/gntdev.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++-
include/xen/gntalloc.h | 28 ++++++++++++++++++++++++
include/xen/gntdev.h | 27 +++++++++++++++++++++++
4 files changed, 165 insertions(+), 1 deletions(-)
diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index a230dc4..8ac0dfc 100644
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -60,11 +60,13 @@
#include <linux/uaccess.h>
#include <linux/types.h>
#include <linux/list.h>
+#include <linux/highmem.h>
#include <xen/xen.h>
#include <xen/page.h>
#include <xen/grant_table.h>
#include <xen/gntalloc.h>
+#include <xen/events.h>
static int limit = 1024;
module_param(limit, int, 0644);
@@ -83,6 +85,9 @@ struct gntalloc_gref {
uint64_t file_index; /* File offset for mmap() */
unsigned int users; /* Use count - when zero, waiting on Xen */
grant_ref_t gref_id; /* The grant reference number */
+ unsigned notify_flags:2; /* Unmap notification flags */
+ unsigned notify_pgoff:12; /* Offset of the byte to clear */
+ int notify_event; /* Port (event channel) to notify */
};
struct gntalloc_file_private_data {
@@ -169,6 +174,16 @@ undo:
static void __del_gref(struct gntalloc_gref *gref)
{
+ if (gref->notify_flags & UNMAP_NOTIFY_CLEAR_BYTE) {
+ uint8_t *tmp = kmap(gref->page);
+ tmp[gref->notify_pgoff] = 0;
+ kunmap(gref->page);
+ }
+ if (gref->notify_flags & UNMAP_NOTIFY_SEND_EVENT)
+ notify_remote_via_evtchn(gref->notify_event);
+
+ gref->notify_flags = 0;
+
if (gnttab_query_foreign_access(gref->gref_id))
return;
@@ -339,6 +354,43 @@ dealloc_grant_out:
return rc;
}
+static long gntalloc_ioctl_notify(struct gntalloc_file_private_data *priv,
+ void __user *arg)
+{
+ struct ioctl_gntalloc_unmap_notify op;
+ struct gntalloc_gref *gref;
+ uint64_t index;
+ int pgoff;
+ int rc;
+
+ if (copy_from_user(&op, arg, sizeof(op)))
+ return -EFAULT;
+
+ index = op.index & ~(PAGE_SIZE - 1);
+ pgoff = op.index & (PAGE_SIZE - 1);
+
+ spin_lock(&gref_lock);
+
+ gref = find_grefs(priv, index, 1);
+ if (!gref) {
+ rc = -ENOENT;
+ goto unlock_out;
+ }
+
+ if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT)) {
+ rc = -EINVAL;
+ goto unlock_out;
+ }
+
+ gref->notify_flags = op.action;
+ gref->notify_pgoff = pgoff;
+ gref->notify_event = op.event_channel_port;
+ rc = 0;
+ unlock_out:
+ spin_unlock(&gref_lock);
+ return rc;
+}
+
static long gntalloc_ioctl(struct file *filp, unsigned int cmd,
unsigned long arg)
{
@@ -351,6 +403,9 @@ static long gntalloc_ioctl(struct file *filp, unsigned int
cmd,
case IOCTL_GNTALLOC_DEALLOC_GREF:
return gntalloc_ioctl_dealloc(priv, (void __user *)arg);
+ case IOCTL_GNTALLOC_SET_UNMAP_NOTIFY:
+ return gntalloc_ioctl_notify(priv, (void __user *)arg);
+
default:
return -ENOIOCTLCMD;
}
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index a5710e8..e360d0a 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -37,6 +37,7 @@
#include <xen/xen.h>
#include <xen/grant_table.h>
#include <xen/gntdev.h>
+#include <xen/events.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/page.h>
@@ -70,6 +71,9 @@ struct grant_map {
int count;
int flags;
int is_mapped;
+ int notify_flags;
+ int notify_offset;
+ int notify_event;
atomic_t users;
struct ioctl_gntdev_grant_ref *grants;
struct gnttab_map_grant_ref *map_ops;
@@ -165,7 +169,7 @@ static struct grant_map *gntdev_find_map_index(struct
gntdev_priv *priv,
list_for_each_entry(map, &priv->maps, next) {
if (map->index != index)
continue;
- if (map->count != count)
+ if (count && map->count != count)
continue;
return map;
}
@@ -184,6 +188,10 @@ static void gntdev_put_map(struct grant_map *map)
atomic_sub(map->count, &pages_mapped);
+ if (map->notify_flags & UNMAP_NOTIFY_SEND_EVENT) {
+ notify_remote_via_evtchn(map->notify_event);
+ }
+
if (map->pages) {
if (!use_ptemod)
unmap_grant_pages(map, 0, map->count);
@@ -272,6 +280,16 @@ static int unmap_grant_pages(struct grant_map *map, int
offset, int pages)
{
int i, err = 0;
+ if (map->notify_flags & UNMAP_NOTIFY_CLEAR_BYTE) {
+ int pgno = (map->notify_offset >> PAGE_SHIFT);
+ if (pgno >= offset && pgno < pages + offset) {
+ uint8_t *tmp = kmap(map->pages[pgno]);
+ tmp[map->notify_offset & (PAGE_SIZE-1)] = 0;
+ kunmap(map->pages[pgno]);
+ map->notify_flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
+ }
+ }
+
pr_debug("map %d+%d [%d+%d]\n", map->index, map->count, offset, pages);
err = gnttab_unmap_refs(map->unmap_ops + offset, map->pages, pages);
if (err)
@@ -517,6 +535,39 @@ static long gntdev_ioctl_get_offset_for_vaddr(struct
gntdev_priv *priv,
return 0;
}
+static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
+{
+ struct ioctl_gntdev_unmap_notify op;
+ struct grant_map *map;
+ int rc;
+
+ if (copy_from_user(&op, u, sizeof(op)))
+ return -EFAULT;
+
+ if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT))
+ return -EINVAL;
+
+ spin_lock(&priv->lock);
+
+ list_for_each_entry(map, &priv->maps, next) {
+ uint64_t begin = map->index << PAGE_SHIFT;
+ uint64_t end = (map->index + map->count) << PAGE_SHIFT;
+ if (op.index >= begin && op.index < end)
+ goto found;
+ }
+ rc = -ENOENT;
+ goto unlock_out;
+
+ found:
+ map->notify_flags = op.action;
+ map->notify_offset = op.index - (map->index << PAGE_SHIFT);
+ map->notify_event = op.event_channel_port;
+ rc = 0;
+ unlock_out:
+ spin_unlock(&priv->lock);
+ return rc;
+}
+
static long gntdev_ioctl(struct file *flip,
unsigned int cmd, unsigned long arg)
{
@@ -533,6 +584,9 @@ static long gntdev_ioctl(struct file *flip,
case IOCTL_GNTDEV_GET_OFFSET_FOR_VADDR:
return gntdev_ioctl_get_offset_for_vaddr(priv, ptr);
+ case IOCTL_GNTDEV_SET_UNMAP_NOTIFY:
+ return gntdev_ioctl_notify(priv, ptr);
+
default:
pr_debug("priv %p, unknown cmd %x\n", priv, cmd);
return -ENOIOCTLCMD;
diff --git a/include/xen/gntalloc.h b/include/xen/gntalloc.h
index e1d6d0f..92339f5 100644
--- a/include/xen/gntalloc.h
+++ b/include/xen/gntalloc.h
@@ -67,4 +67,32 @@ struct ioctl_gntalloc_dealloc_gref {
/* Number of references to unmap */
uint32_t count;
};
+
+/*
+ * Sets up an unmap notification within the page, so that the other side can do
+ * cleanup if this side crashes. Required to implement cross-domain robust
+ * mutexes or close notification on communication channels.
+ *
+ * Each mapped page only supports one notification; multiple calls referring to
+ * the same page overwrite the previous notification. You must clear the
+ * notification prior to the IOCTL_GNTALLOC_DEALLOC_GREF if you do not want it
+ * to occur.
+ */
+#define IOCTL_GNTALLOC_SET_UNMAP_NOTIFY \
+_IOC(_IOC_NONE, 'G', 7, sizeof(struct ioctl_gntalloc_unmap_notify))
+struct ioctl_gntalloc_unmap_notify {
+ /* IN parameters */
+ /* Index of a byte in the page */
+ uint64_t index;
+ /* Action(s) to take on unmap */
+ uint32_t action;
+ /* Event channel to notify */
+ uint32_t event_channel_port;
+};
+
+/* Clear (set to zero) the byte specified by index */
+#define UNMAP_NOTIFY_CLEAR_BYTE 0x1
+/* Send an interrupt on the indicated event channel */
+#define UNMAP_NOTIFY_SEND_EVENT 0x2
+
#endif /* __LINUX_PUBLIC_GNTALLOC_H__ */
diff --git a/include/xen/gntdev.h b/include/xen/gntdev.h
index eb23f41..5d9b9b4 100644
--- a/include/xen/gntdev.h
+++ b/include/xen/gntdev.h
@@ -116,4 +116,31 @@ struct ioctl_gntdev_set_max_grants {
uint32_t count;
};
+/*
+ * Sets up an unmap notification within the page, so that the other side can do
+ * cleanup if this side crashes. Required to implement cross-domain robust
+ * mutexes or close notification on communication channels.
+ *
+ * Each mapped page only supports one notification; multiple calls referring to
+ * the same page overwrite the previous notification. You must clear the
+ * notification prior to the IOCTL_GNTALLOC_DEALLOC_GREF if you do not want it
+ * to occur.
+ */
+#define IOCTL_GNTDEV_SET_UNMAP_NOTIFY \
+_IOC(_IOC_NONE, 'G', 7, sizeof(struct ioctl_gntdev_unmap_notify))
+struct ioctl_gntdev_unmap_notify {
+ /* IN parameters */
+ /* Index of a byte in the page */
+ uint64_t index;
+ /* Action(s) to take on unmap */
+ uint32_t action;
+ /* Event channel to notify */
+ uint32_t event_channel_port;
+};
+
+/* Clear (set to zero) the byte specified by index */
+#define UNMAP_NOTIFY_CLEAR_BYTE 0x1
+/* Send an interrupt on the indicated event channel */
+#define UNMAP_NOTIFY_SEND_EVENT 0x2
+
#endif /* __LINUX_PUBLIC_GNTDEV_H__ */
--
1.7.3.4
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