The vq->is_le field is used to fix endianness when accessing the vring via
the cpu_to_vhost16() and vhost16_to_cpu() helpers in the following cases:
1) host is big endian and device is modern virtio
2) host has cross-endian support and device is legacy virtio with a different
endianness than the host
Both cases rely on the VHOST_SET_FEATURES ioctl, but 2) also needs the
VHOST_SET_VRING_ENDIAN ioctl to be called by userspace. Since vq->is_le
is only needed when the backend is active, it was decided to set it at
backend start.
This is currently done in vhost_init_used()->vhost_init_is_le() but it
obfuscates the core vhost code. This patch moves the is_le setup to a
dedicated function that is called from the backend code.
Note vhost_net is the only backend that can pass vq->private_data == NULL to
vhost_init_used(), hence the "if (sock)" branch.
No behaviour change.
Reviewed-by: Cornelia Huck <cornelia.huck at de.ibm.com>
Signed-off-by: Greg Kurz <gkurz at linux.vnet.ibm.com>
---
Hi Michael,
This is a cleanup patch I had posted last year:
http://patchwork.ozlabs.org/patch/538277/
I am just reposting with Cornelia's R-b.
Cheers.
--
Greg
drivers/vhost/net.c | 6 ++++++
drivers/vhost/scsi.c | 3 +++
drivers/vhost/test.c | 2 ++
drivers/vhost/vhost.c | 12 +++++++-----
drivers/vhost/vhost.h | 1 +
5 files changed, 19 insertions(+), 5 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 9eda69e40678..d6319cb2664c 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -917,6 +917,12 @@ static long vhost_net_set_backend(struct vhost_net *n,
unsigned index, int fd)
vhost_net_disable_vq(n, vq);
vq->private_data = sock;
+
+ if (sock)
+ vhost_set_is_le(vq);
+ else
+ vq->is_le = virtio_legacy_is_little_endian();
+
r = vhost_init_used(vq);
if (r)
goto err_used;
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 29cfc57d496e..1f4f405ebba8 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1274,6 +1274,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
vq = &vs->vqs[i].vq;
mutex_lock(&vq->mutex);
vq->private_data = vs_tpg;
+
+ vhost_set_is_le(vq);
+
vhost_init_used(vq);
mutex_unlock(&vq->mutex);
}
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index f2882ac98726..b1c7df502211 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int test)
oldpriv = vq->private_data;
vq->private_data = priv;
+ vhost_set_is_le(vq);
+
r = vhost_init_used(&n->vqs[index]);
mutex_unlock(&vq->mutex);
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index ad2146a9ab2d..e688eb801d43 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -113,6 +113,12 @@ static void vhost_init_is_le(struct vhost_virtqueue *vq)
}
#endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
+void vhost_set_is_le(struct vhost_virtqueue *vq)
+{
+ vhost_init_is_le(vq);
+}
+EXPORT_SYMBOL_GPL(vhost_set_is_le);
+
static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
{
@@ -1156,12 +1162,8 @@ int vhost_init_used(struct vhost_virtqueue *vq)
{
__virtio16 last_used_idx;
int r;
- if (!vq->private_data) {
- vq->is_le = virtio_legacy_is_little_endian();
+ if (!vq->private_data)
return 0;
- }
-
- vhost_init_is_le(vq);
r = vhost_update_used_flags(vq);
if (r)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index d3f767448a72..af5d33797937 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -162,6 +162,7 @@ bool vhost_enable_notify(struct vhost_dev *, struct
vhost_virtqueue *);
int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
unsigned int log_num, u64 len);
+void vhost_set_is_le(struct vhost_virtqueue *vq);
#define vq_err(vq, fmt, ...) do { \
pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \
On Mon, Jan 11, 2016 at 03:39:38PM +0100, Greg Kurz wrote:> The vq->is_le field is used to fix endianness when accessing the vring via > the cpu_to_vhost16() and vhost16_to_cpu() helpers in the following cases: > > 1) host is big endian and device is modern virtio > > 2) host has cross-endian support and device is legacy virtio with a different > endianness than the host > > Both cases rely on the VHOST_SET_FEATURES ioctl, but 2) also needs the > VHOST_SET_VRING_ENDIAN ioctl to be called by userspace. Since vq->is_le > is only needed when the backend is active, it was decided to set it at > backend start. > > This is currently done in vhost_init_used()->vhost_init_is_le() but it > obfuscates the core vhost code. This patch moves the is_le setup to a > dedicated function that is called from the backend code. > > Note vhost_net is the only backend that can pass vq->private_data == NULL to > vhost_init_used(), hence the "if (sock)" branch. > > No behaviour change. > > Reviewed-by: Cornelia Huck <cornelia.huck at de.ibm.com> > Signed-off-by: Greg Kurz <gkurz at linux.vnet.ibm.com> > --- > > Hi Michael, > > This is a cleanup patch I had posted last year: > > http://patchwork.ozlabs.org/patch/538277/ > > I am just reposting with Cornelia's R-b. > > Cheers. > > -- > Greg > > drivers/vhost/net.c | 6 ++++++ > drivers/vhost/scsi.c | 3 +++ > drivers/vhost/test.c | 2 ++ > drivers/vhost/vhost.c | 12 +++++++----- > drivers/vhost/vhost.h | 1 + > 5 files changed, 19 insertions(+), 5 deletions(-) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index 9eda69e40678..d6319cb2664c 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -917,6 +917,12 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd) > > vhost_net_disable_vq(n, vq); > vq->private_data = sock; > + > + if (sock) > + vhost_set_is_le(vq); > + else > + vq->is_le = virtio_legacy_is_little_endian(); > + > r = vhost_init_used(vq); > if (r) > goto err_used;This part is kind of ugly. I think it's cleaner is the generic code. How about we teach vhost_set_is_le to test vq->private_data and DTRT?> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c > index 29cfc57d496e..1f4f405ebba8 100644 > --- a/drivers/vhost/scsi.c > +++ b/drivers/vhost/scsi.c > @@ -1274,6 +1274,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs, > vq = &vs->vqs[i].vq; > mutex_lock(&vq->mutex); > vq->private_data = vs_tpg; > + > + vhost_set_is_le(vq); > + > vhost_init_used(vq); > mutex_unlock(&vq->mutex); > } > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c > index f2882ac98726..b1c7df502211 100644 > --- a/drivers/vhost/test.c > +++ b/drivers/vhost/test.c > @@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int test) > oldpriv = vq->private_data; > vq->private_data = priv; > > + vhost_set_is_le(vq); > + > r = vhost_init_used(&n->vqs[index]); > > mutex_unlock(&vq->mutex); > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index ad2146a9ab2d..e688eb801d43 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -113,6 +113,12 @@ static void vhost_init_is_le(struct vhost_virtqueue *vq) > } > #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */ > > +void vhost_set_is_le(struct vhost_virtqueue *vq) > +{ > + vhost_init_is_le(vq); > +} > +EXPORT_SYMBOL_GPL(vhost_set_is_le); > + > static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh, > poll_table *pt) > {Why do we need this wrapper? Why not just export vhost_init_is_le? Or rename vhost_init_is_le->vhost_set_is_le if you prefer.> @@ -1156,12 +1162,8 @@ int vhost_init_used(struct vhost_virtqueue *vq) > { > __virtio16 last_used_idx; > int r; > - if (!vq->private_data) { > - vq->is_le = virtio_legacy_is_little_endian(); > + if (!vq->private_data) > return 0; > - } > - > - vhost_init_is_le(vq); > > r = vhost_update_used_flags(vq); > if (r) > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > index d3f767448a72..af5d33797937 100644 > --- a/drivers/vhost/vhost.h > +++ b/drivers/vhost/vhost.h > @@ -162,6 +162,7 @@ bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *); > > int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, > unsigned int log_num, u64 len); > +void vhost_set_is_le(struct vhost_virtqueue *vq); > > #define vq_err(vq, fmt, ...) do { \ > pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \
On Tue, 12 Jan 2016 12:01:32 +0200 "Michael S. Tsirkin" <mst at redhat.com> wrote:> On Mon, Jan 11, 2016 at 03:39:38PM +0100, Greg Kurz wrote: > > The vq->is_le field is used to fix endianness when accessing the vring via > > the cpu_to_vhost16() and vhost16_to_cpu() helpers in the following cases: > > > > 1) host is big endian and device is modern virtio > > > > 2) host has cross-endian support and device is legacy virtio with a different > > endianness than the host > > > > Both cases rely on the VHOST_SET_FEATURES ioctl, but 2) also needs the > > VHOST_SET_VRING_ENDIAN ioctl to be called by userspace. Since vq->is_le > > is only needed when the backend is active, it was decided to set it at > > backend start. > > > > This is currently done in vhost_init_used()->vhost_init_is_le() but it > > obfuscates the core vhost code. This patch moves the is_le setup to a > > dedicated function that is called from the backend code. > > > > Note vhost_net is the only backend that can pass vq->private_data == NULL to > > vhost_init_used(), hence the "if (sock)" branch. > > > > No behaviour change. > > > > Reviewed-by: Cornelia Huck <cornelia.huck at de.ibm.com> > > Signed-off-by: Greg Kurz <gkurz at linux.vnet.ibm.com> > > --- > > > > Hi Michael, > > > > This is a cleanup patch I had posted last year: > > > > http://patchwork.ozlabs.org/patch/538277/ > > > > I am just reposting with Cornelia's R-b. > > > > Cheers. > > > > -- > > Greg > > > > drivers/vhost/net.c | 6 ++++++ > > drivers/vhost/scsi.c | 3 +++ > > drivers/vhost/test.c | 2 ++ > > drivers/vhost/vhost.c | 12 +++++++----- > > drivers/vhost/vhost.h | 1 + > > 5 files changed, 19 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > index 9eda69e40678..d6319cb2664c 100644 > > --- a/drivers/vhost/net.c > > +++ b/drivers/vhost/net.c > > @@ -917,6 +917,12 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd) > > > > vhost_net_disable_vq(n, vq); > > vq->private_data = sock; > > + > > + if (sock) > > + vhost_set_is_le(vq); > > + else > > + vq->is_le = virtio_legacy_is_little_endian(); > > + > > r = vhost_init_used(vq); > > if (r) > > goto err_used; > > This part is kind of ugly. I think it's cleaner is the generic code. > How about we teach vhost_set_is_le to test vq->private_data and DTRT? >You're right. I'll try that.> > diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c > > index 29cfc57d496e..1f4f405ebba8 100644 > > --- a/drivers/vhost/scsi.c > > +++ b/drivers/vhost/scsi.c > > @@ -1274,6 +1274,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs, > > vq = &vs->vqs[i].vq; > > mutex_lock(&vq->mutex); > > vq->private_data = vs_tpg; > > + > > + vhost_set_is_le(vq); > > + > > vhost_init_used(vq); > > mutex_unlock(&vq->mutex); > > } > > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c > > index f2882ac98726..b1c7df502211 100644 > > --- a/drivers/vhost/test.c > > +++ b/drivers/vhost/test.c > > @@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int test) > > oldpriv = vq->private_data; > > vq->private_data = priv; > > > > + vhost_set_is_le(vq); > > + > > r = vhost_init_used(&n->vqs[index]); > > > > mutex_unlock(&vq->mutex); > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > index ad2146a9ab2d..e688eb801d43 100644 > > --- a/drivers/vhost/vhost.c > > +++ b/drivers/vhost/vhost.c > > @@ -113,6 +113,12 @@ static void vhost_init_is_le(struct vhost_virtqueue *vq) > > } > > #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */ > > > > +void vhost_set_is_le(struct vhost_virtqueue *vq) > > +{ > > + vhost_init_is_le(vq); > > +} > > +EXPORT_SYMBOL_GPL(vhost_set_is_le); > > + > > static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh, > > poll_table *pt) > > { > > Why do we need this wrapper? Why not just export vhost_init_is_le?This is a tentative workaround to: WARNING: EXPORT_SYMBOL(foo); should immediately follow its function/variable #35: FILE: drivers/vhost/vhost.c:116: +EXPORT_SYMBOL_GPL(vhost_init_is_le); Other possibility is to put the EXPORT_SYMBOL_GPL statement in both conditional compilation blocks. Maybe better ?> Or rename vhost_init_is_le->vhost_set_is_le if you prefer. > > > @@ -1156,12 +1162,8 @@ int vhost_init_used(struct vhost_virtqueue *vq) > > { > > __virtio16 last_used_idx; > > int r; > > - if (!vq->private_data) { > > - vq->is_le = virtio_legacy_is_little_endian(); > > + if (!vq->private_data) > > return 0; > > - } > > - > > - vhost_init_is_le(vq); > > > > r = vhost_update_used_flags(vq); > > if (r) > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > index d3f767448a72..af5d33797937 100644 > > --- a/drivers/vhost/vhost.h > > +++ b/drivers/vhost/vhost.h > > @@ -162,6 +162,7 @@ bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *); > > > > int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, > > unsigned int log_num, u64 len); > > +void vhost_set_is_le(struct vhost_virtqueue *vq); > > > > #define vq_err(vq, fmt, ...) do { \ > > pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \ >