search for: vhost_set_vring_endian

...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. + + 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 by default. + + If unsure, say "N". diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 2ee2826..9e8e004 100644 --- a/drivers/v...

...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/vhos...

...p--- > + 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/vh...

...p--- > + 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/vh...

...erent 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". > > di...

...at does it mean to disable big endian? Make it little endian? Existing reset seems to make sense. > +static void vhost_enable_user_be(struct vhost_virtqueue *vq, bool user_be) > +{ > + vq->user_be = user_be; > +} > + And this is maybe "init_user_be"? > static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > { > struct vhost_vring_state s; > @@ -62,7 +67,7 @@ static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > s.num != VHOST_VRING_BIG_ENDIAN) > return -EINVAL; > > - vq->user_be = s.num;...

...at does it mean to disable big endian? Make it little endian? Existing reset seems to make sense. > +static void vhost_enable_user_be(struct vhost_virtqueue *vq, bool user_be) > +{ > + vq->user_be = user_be; > +} > + And this is maybe "init_user_be"? > static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > { > struct vhost_vring_state s; > @@ -62,7 +67,7 @@ static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > s.num != VHOST_VRING_BIG_ENDIAN) > return -EINVAL; > > - vq->user_be = s.num;...

...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 functi...

...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 functi...

...> > > + vq->user_be = user_be; > > > +} > > > + > > > > And this is maybe "init_user_be"? > > > > Anyway I don't mind changing the names to reset/init_user_be if you think it > is clearer. > > > > static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > > > { > > > struct vhost_vring_state s; > > > @@ -62,7 +67,7 @@ static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > > > s.num != VHOST_VRING_BIG_ENDIAN) > > > retu...

...> > > + vq->user_be = user_be; > > > +} > > > + > > > > And this is maybe "init_user_be"? > > > > Anyway I don't mind changing the names to reset/init_user_be if you think it > is clearer. > > > > static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > > > { > > > struct vhost_vring_state s; > > > @@ -62,7 +67,7 @@ static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > > > s.num != VHOST_VRING_BIG_ENDIAN) > > > retu...

Hi, This patchset allows vhost to be used with legacy virtio when guest and host have a different endianness. It is compatible with modern virtio and can be fully compiled out through kernel config. FWIW, I could flawlessly kexec/reboot guests from ppc64 to ppc64le and back. I could also migrate from a ppc64 to a ppc64le host and back. No regressions on x86 as expected. My experimental QEMU tree

Hi, This patchset allows vhost to be used with legacy virtio when guest and host have a different endianness. It is compatible with modern virtio and can be fully compiled out through kernel config. FWIW, I could flawlessly kexec/reboot guests from ppc64 to ppc64le and back. I could also migrate from a ppc64 to a ppc64le host and back. No regressions on x86 as expected. My experimental QEMU tree

...host_vq_reset_user_be(struct vhost_virtqueue *vq) +static void vhost_disable_user_be(struct vhost_virtqueue *vq) { vq->user_be = !virtio_legacy_is_little_endian(); } +static void vhost_enable_user_be(struct vhost_virtqueue *vq, bool user_be) +{ + vq->user_be = user_be; +} + static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) { struct vhost_vring_state s; @@ -62,7 +67,7 @@ static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) s.num != VHOST_VRING_BIG_ENDIAN) return -EINVAL; - vq->user_be = s.num; + vhost_enable_user_be(vq, !!s.num)...

...(struct vhost_virtqueue *vq, bool user_be) > > +{ > > + vq->user_be = user_be; > > +} > > + > > And this is maybe "init_user_be"? > Anyway I don't mind changing the names to reset/init_user_be if you think it is clearer. > > static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > > { > > struct vhost_vring_state s; > > @@ -62,7 +67,7 @@ static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) > > s.num != VHOST_VRING_BIG_ENDIAN) > > return -EINVAL; > > &...

...| 76 +++++++++++++++++++++++++++++++++++++++++++- > > > drivers/vhost/vhost.h | 12 +++++-- > > > include/uapi/linux/vhost.h | 9 +++++ > > > 4 files changed, 103 insertions(+), 4 deletions(-) > > > > > > Changes since v3: > > > - VHOST_SET_VRING_ENDIAN_LEGACY ioctl renamed to VHOST_SET_VRING_BIG_ENDIAN > > > - ioctl API is now: 0 for le, 1 for be, other values are EINVAL > > > - ioctl doesn't filter out modern devices > > > - ioctl stubs return ENOIOCTLCMD > > > - forbid endianness changes when vring is act...

...| 76 +++++++++++++++++++++++++++++++++++++++++++- > > > drivers/vhost/vhost.h | 12 +++++-- > > > include/uapi/linux/vhost.h | 9 +++++ > > > 4 files changed, 103 insertions(+), 4 deletions(-) > > > > > > Changes since v3: > > > - VHOST_SET_VRING_ENDIAN_LEGACY ioctl renamed to VHOST_SET_VRING_BIG_ENDIAN > > > - ioctl API is now: 0 for le, 1 for be, other values are EINVAL > > > - ioctl doesn't filter out modern devices > > > - ioctl stubs return ENOIOCTLCMD > > > - forbid endianness changes when vring is act...

This series is a respin of the following patch: http://patchwork.ozlabs.org/patch/565921/ Patch 1 is preliminary work: it gives better names to the helpers that are involved in cross-endian support. Patch 2 is actually a v2 of the original patch. All devices now call a helper in the generic code, which DTRT according to vq->private_data, as suggested by Michael. --- Greg Kurz (2):

This series is a respin of the following patch: http://patchwork.ozlabs.org/patch/565921/ Patch 1 is preliminary work: it gives better names to the helpers that are involved in cross-endian support. Patch 2 is actually a v2 of the original patch. All devices now call a helper in the generic code, which DTRT according to vq->private_data, as suggested by Michael. --- Greg Kurz (2):

...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 functi...