Re: [PATCH v5 7/8] vhost: cross-endian support for legacy devices
On Fri, 24 Apr 2015 10:06:19 +0200
Greg Kurz gk...@linux.vnet.ibm.com wrote:
On Fri, 24 Apr 2015 09:19:26 +0200
Cornelia Huck cornelia.h...@de.ibm.com wrote:
On Thu, 23 Apr 2015 17:29:42 +0200
Greg Kurz gk...@linux.vnet.ibm.com wrote:
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index bb6a5b4..b980b53 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -103,6 +103,18 @@ struct vhost_memory {
/* Get accessor: reads index, writes value in num */
#define VHOST_GET_VRING_BASE _IOWR(VHOST_VIRTIO, 0x12, struct
vhost_vring_state)
+/* Set the vring byte order in num. Valid values are
VHOST_VRING_LITTLE_ENDIAN
+ * or VHOST_VRING_BIG_ENDIAN (other values return EINVAL).
-EINVAL?
Oops, yes. :)
Should you also mention when you return -EBUSY?
Indeed... what about:
The byte order cannot be changed when the device is active: trying to do so
returns -EBUSY.
s/when/while/ ?
But sounds good.
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Re: [PATCH v5 7/8] vhost: cross-endian support for legacy devices
On Fri, 24 Apr 2015 09:19:26 +0200
Cornelia Huck cornelia.h...@de.ibm.com wrote:
On Thu, 23 Apr 2015 17:29:42 +0200
Greg Kurz gk...@linux.vnet.ibm.com wrote:
This patch brings cross-endian support to vhost when used to implement
legacy virtio devices. Since it is a relatively rare situation, the
feature availability is controlled by a kernel config option (not set
by default).
The vq-is_le boolean field is added to cache the endianness to be
used for ring accesses. It defaults to native endian, as expected
by legacy virtio devices. When the ring gets active, we force little
endian if the device is modern. When the ring is deactivated, we
revert to the native endian default.
If cross-endian was compiled in, a vq-user_be boolean field is added
so that userspace may request a specific endianness. This field is
used to override the default when activating the ring of a legacy
device. It has no effect on modern devices.
Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
Changes since v4:
- rewrote patch title to mention cross-endian
- renamed config to VHOST_CROSS_ENDIAN_LEGACY
- rewrote config description and help
- moved ifdefery to top of vhost.c
- added a detailed comment about the lifecycle of vq-user_be in
vhost_init_is_le()
- renamed ioctls to VHOST_[GS]ET_VRING_ENDIAN
- added LE/BE defines to the ioctl API
- rewrote ioctl sanity check with the LE/BE defines
- updated comment in uapi/linux/vhost.h to mention that the availibility
of both SET and GET ioctls depends on the kernel config
drivers/vhost/Kconfig | 15
drivers/vhost/vhost.c | 86
+++-
drivers/vhost/vhost.h | 10 +
include/uapi/linux/vhost.h | 12 ++
4 files changed, 121 insertions(+), 2 deletions(-)
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 017a1e8..74d7380 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -32,3 +32,18 @@ config VHOST
---help---
This option is selected by any driver which needs to access
the core of vhost.
+
+config VHOST_CROSS_ENDIAN_LEGACY
+ bool Cross-endian support for vhost
+ default n
+ ---help---
+ This option allows vhost to support guests with a different byte
+ ordering from host.
...while using legacy virtio.
Might help to explain the LEGACY in the config option ;)
Makes sense indeed !
+
+ Userspace programs can control the feature using the
+ VHOST_SET_VRING_ENDIAN and VHOST_GET_VRING_ENDIAN ioctls.
+
+ This is only useful on a few platforms (ppc64 and arm64). Since it
+ adds some overhead, it is disabled default.
s/default/by default/
Ok.
+
+ If unsure, say N.
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..8c4390d 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -36,6 +36,78 @@ enum {
#define vhost_used_event(vq) ((__virtio16 __user
*)vq-avail-ring[vq-num])
#define vhost_avail_event(vq) ((__virtio16 __user
*)vq-used-ring[vq-num])
+#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+ vq-user_be = !virtio_legacy_is_little_endian();
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user
*argp)
+{
+ struct vhost_vring_state s;
+
+ if (vq-private_data)
+ return -EBUSY;
+
+ if (copy_from_user(s, argp, sizeof(s)))
+ return -EFAULT;
+
+ if (s.num != VHOST_VRING_LITTLE_ENDIAN
+ s.num != VHOST_VRING_BIG_ENDIAN)
+ return -EINVAL;
+
+ vq-user_be = s.num;
+
+ return 0;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+ int __user *argp)
+{
+ struct vhost_vring_state s = {
+ .index = idx,
+ .num = vq-user_be
+ };
+
+ if (copy_to_user(argp, s, sizeof(s)))
+ return -EFAULT;
+
+ return 0;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+ /* Note for legacy virtio: user_be is initialized at reset time
+* according to the host endianness. If userspace does not set an
+* explicit endianness, the default behavior is native endian, as
+* expected by legacy virtio.
+*/
+ vq-is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq-user_be;
+}
+#else
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+ ;
Just leave the function body empty?
Ok.
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user
*argp)
+{
+ return -ENOIOCTLCMD;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+ int __user *argp)
+{
+ return -ENOIOCTLCMD;
+}
+
+static void
Re: [PATCH v5 7/8] vhost: cross-endian support for legacy devices
On Thu, 23 Apr 2015 17:29:42 +0200
Greg Kurz gk...@linux.vnet.ibm.com wrote:
This patch brings cross-endian support to vhost when used to implement
legacy virtio devices. Since it is a relatively rare situation, the
feature availability is controlled by a kernel config option (not set
by default).
The vq-is_le boolean field is added to cache the endianness to be
used for ring accesses. It defaults to native endian, as expected
by legacy virtio devices. When the ring gets active, we force little
endian if the device is modern. When the ring is deactivated, we
revert to the native endian default.
If cross-endian was compiled in, a vq-user_be boolean field is added
so that userspace may request a specific endianness. This field is
used to override the default when activating the ring of a legacy
device. It has no effect on modern devices.
Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
Changes since v4:
- rewrote patch title to mention cross-endian
- renamed config to VHOST_CROSS_ENDIAN_LEGACY
- rewrote config description and help
- moved ifdefery to top of vhost.c
- added a detailed comment about the lifecycle of vq-user_be in
vhost_init_is_le()
- renamed ioctls to VHOST_[GS]ET_VRING_ENDIAN
- added LE/BE defines to the ioctl API
- rewrote ioctl sanity check with the LE/BE defines
- updated comment in uapi/linux/vhost.h to mention that the availibility
of both SET and GET ioctls depends on the kernel config
drivers/vhost/Kconfig | 15
drivers/vhost/vhost.c | 86
+++-
drivers/vhost/vhost.h | 10 +
include/uapi/linux/vhost.h | 12 ++
4 files changed, 121 insertions(+), 2 deletions(-)
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 017a1e8..74d7380 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -32,3 +32,18 @@ config VHOST
---help---
This option is selected by any driver which needs to access
the core of vhost.
+
+config VHOST_CROSS_ENDIAN_LEGACY
+ bool Cross-endian support for vhost
+ default n
+ ---help---
+ This option allows vhost to support guests with a different byte
+ ordering from host.
...while using legacy virtio.
Might help to explain the LEGACY in the config option ;)
+
+ Userspace programs can control the feature using the
+ VHOST_SET_VRING_ENDIAN and VHOST_GET_VRING_ENDIAN ioctls.
+
+ This is only useful on a few platforms (ppc64 and arm64). Since it
+ adds some overhead, it is disabled default.
s/default/by default/
+
+ If unsure, say N.
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..8c4390d 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -36,6 +36,78 @@ enum {
#define vhost_used_event(vq) ((__virtio16 __user *)vq-avail-ring[vq-num])
#define vhost_avail_event(vq) ((__virtio16 __user *)vq-used-ring[vq-num])
+#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+ vq-user_be = !virtio_legacy_is_little_endian();
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user
*argp)
+{
+ struct vhost_vring_state s;
+
+ if (vq-private_data)
+ return -EBUSY;
+
+ if (copy_from_user(s, argp, sizeof(s)))
+ return -EFAULT;
+
+ if (s.num != VHOST_VRING_LITTLE_ENDIAN
+ s.num != VHOST_VRING_BIG_ENDIAN)
+ return -EINVAL;
+
+ vq-user_be = s.num;
+
+ return 0;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+int __user *argp)
+{
+ struct vhost_vring_state s = {
+ .index = idx,
+ .num = vq-user_be
+ };
+
+ if (copy_to_user(argp, s, sizeof(s)))
+ return -EFAULT;
+
+ return 0;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+ /* Note for legacy virtio: user_be is initialized at reset time
+ * according to the host endianness. If userspace does not set an
+ * explicit endianness, the default behavior is native endian, as
+ * expected by legacy virtio.
+ */
+ vq-is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq-user_be;
+}
+#else
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+ ;
Just leave the function body empty?
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user
*argp)
+{
+ return -ENOIOCTLCMD;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+int __user *argp)
+{
+ return -ENOIOCTLCMD;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+ if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+ vq-is_le = true;
+}
+#endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
+
[PATCH v5 7/8] vhost: cross-endian support for legacy devices
This patch brings cross-endian support to vhost when used to implement
legacy virtio devices. Since it is a relatively rare situation, the
feature availability is controlled by a kernel config option (not set
by default).
The vq-is_le boolean field is added to cache the endianness to be
used for ring accesses. It defaults to native endian, as expected
by legacy virtio devices. When the ring gets active, we force little
endian if the device is modern. When the ring is deactivated, we
revert to the native endian default.
If cross-endian was compiled in, a vq-user_be boolean field is added
so that userspace may request a specific endianness. This field is
used to override the default when activating the ring of a legacy
device. It has no effect on modern devices.
Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
Changes since v4:
- rewrote patch title to mention cross-endian
- renamed config to VHOST_CROSS_ENDIAN_LEGACY
- rewrote config description and help
- moved ifdefery to top of vhost.c
- added a detailed comment about the lifecycle of vq-user_be in
vhost_init_is_le()
- renamed ioctls to VHOST_[GS]ET_VRING_ENDIAN
- added LE/BE defines to the ioctl API
- rewrote ioctl sanity check with the LE/BE defines
- updated comment in uapi/linux/vhost.h to mention that the availibility
of both SET and GET ioctls depends on the kernel config
drivers/vhost/Kconfig | 15
drivers/vhost/vhost.c | 86 +++-
drivers/vhost/vhost.h | 10 +
include/uapi/linux/vhost.h | 12 ++
4 files changed, 121 insertions(+), 2 deletions(-)
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 017a1e8..74d7380 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -32,3 +32,18 @@ config VHOST
---help---
This option is selected by any driver which needs to access
the core of vhost.
+
+config VHOST_CROSS_ENDIAN_LEGACY
+ bool Cross-endian support for vhost
+ default n
+ ---help---
+ This option allows vhost to support guests with a different byte
+ ordering from host.
+
+ Userspace programs can control the feature using the
+ VHOST_SET_VRING_ENDIAN and VHOST_GET_VRING_ENDIAN ioctls.
+
+ This is only useful on a few platforms (ppc64 and arm64). Since it
+ adds some overhead, it is disabled default.
+
+ If unsure, say N.
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..8c4390d 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -36,6 +36,78 @@ enum {
#define vhost_used_event(vq) ((__virtio16 __user *)vq-avail-ring[vq-num])
#define vhost_avail_event(vq) ((__virtio16 __user *)vq-used-ring[vq-num])
+#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+ vq-user_be = !virtio_legacy_is_little_endian();
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user
*argp)
+{
+ struct vhost_vring_state s;
+
+ if (vq-private_data)
+ return -EBUSY;
+
+ if (copy_from_user(s, argp, sizeof(s)))
+ return -EFAULT;
+
+ if (s.num != VHOST_VRING_LITTLE_ENDIAN
+ s.num != VHOST_VRING_BIG_ENDIAN)
+ return -EINVAL;
+
+ vq-user_be = s.num;
+
+ return 0;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+ int __user *argp)
+{
+ struct vhost_vring_state s = {
+ .index = idx,
+ .num = vq-user_be
+ };
+
+ if (copy_to_user(argp, s, sizeof(s)))
+ return -EFAULT;
+
+ return 0;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+ /* Note for legacy virtio: user_be is initialized at reset time
+* according to the host endianness. If userspace does not set an
+* explicit endianness, the default behavior is native endian, as
+* expected by legacy virtio.
+*/
+ vq-is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq-user_be;
+}
+#else
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+ ;
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user
*argp)
+{
+ return -ENOIOCTLCMD;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+ int __user *argp)
+{
+ return -ENOIOCTLCMD;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+ if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+ vq-is_le = true;
+}
+#endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
+
static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
{
@@ -199,6 +271,8 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq-call = NULL;
vq-log_ctx = NULL;
vq-memory = NULL;
+ vq-is_le =
