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xen/gntalloc,gntdev: Add unmap notify ioctl
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This ioctl allows the users of a shared page to be notified when
the other end exits abnormally.

[v2: updated description in structs]
Signed-off-by: Daniel De Graaf <[email protected]>
Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
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@dgdegraaf @konradwilk
dgdegraaf authored and konradwilk committed Feb 14, 2011
1 parent dd31405 commit bdc612d
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Showing 4 changed files with 182 additions and 1 deletion.
59 changes: 59 additions & 0 deletions drivers/xen/gntalloc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand All @@ -75,6 +77,12 @@ static LIST_HEAD(gref_list);
static DEFINE_SPINLOCK(gref_lock);
static int gref_size;

struct notify_info {
uint16_t pgoff:12; /* Bits 0-11: Offset of the byte to clear */
uint16_t flags:2; /* Bits 12-13: Unmap notification flags */
int event; /* Port (event channel) to notify */
};

/* Metadata on a grant reference. */
struct gntalloc_gref {
struct list_head next_gref; /* list entry gref_list */
Expand All @@ -83,6 +91,7 @@ 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 */
struct notify_info notify; /* Unmap notification */
};

struct gntalloc_file_private_data {
Expand Down Expand Up @@ -164,6 +173,16 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,

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 (gref->gref_id > 0) {
if (gnttab_query_foreign_access(gref->gref_id))
return;
Expand Down Expand Up @@ -349,6 +368,43 @@ static long gntalloc_ioctl_dealloc(struct gntalloc_file_private_data *priv,
return rc;
}

static long gntalloc_ioctl_unmap_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)
{
Expand All @@ -361,6 +417,9 @@ 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_unmap_notify(priv, (void __user *)arg);

default:
return -ENOIOCTLCMD;
}
Expand Down
61 changes: 60 additions & 1 deletion drivers/xen/gntdev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand All @@ -63,6 +64,13 @@ struct gntdev_priv {
struct mmu_notifier mn;
};

struct unmap_notify {
int flags;
/* Address relative to the start of the grant_map */
int addr;
int event;
};

struct grant_map {
struct list_head next;
struct vm_area_struct *vma;
Expand All @@ -71,6 +79,7 @@ struct grant_map {
int flags;
int is_mapped;
atomic_t users;
struct unmap_notify notify;
struct ioctl_gntdev_grant_ref *grants;
struct gnttab_map_grant_ref *map_ops;
struct gnttab_unmap_grant_ref *unmap_ops;
Expand Down Expand Up @@ -165,7 +174,7 @@ 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;
}
Expand All @@ -184,6 +193,10 @@ 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);
Expand Down Expand Up @@ -274,6 +287,16 @@ 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.addr >> PAGE_SHIFT);
if (pgno >= offset && pgno < offset + pages) {
uint8_t *tmp = kmap(map->pages[pgno]);
tmp[map->notify.addr & (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)
Expand Down Expand Up @@ -519,6 +542,39 @@ 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.addr = 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)
{
Expand All @@ -535,6 +591,9 @@ 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;
Expand Down
32 changes: 32 additions & 0 deletions include/xen/gntalloc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,4 +47,36 @@ 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 */
/* Offset in the file descriptor for a byte within the page (same as
* used in mmap). If using UNMAP_NOTIFY_CLEAR_BYTE, this is the byte to
* be cleared. Otherwise, it can be any byte in the page whose
* notification we are adjusting.
*/
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__ */
31 changes: 31 additions & 0 deletions include/xen/gntdev.h
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Original file line number Diff line number Diff line change
Expand Up @@ -116,4 +116,35 @@ 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 */
/* Offset in the file descriptor for a byte within the page (same as
* used in mmap). If using UNMAP_NOTIFY_CLEAR_BYTE, this is the byte to
* be cleared. Otherwise, it can be any byte in the page whose
* notification we are adjusting.
*/
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__ */

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