diff options
| -rw-r--r-- | drivers/vhost/Kconfig | 15 | ||||
| -rw-r--r-- | drivers/vhost/vhost.c | 85 | ||||
| -rw-r--r-- | drivers/vhost/vhost.h | 11 | ||||
| -rw-r--r-- | include/uapi/linux/vhost.h | 14 |
4 files changed, 122 insertions, 3 deletions
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig index 017a1e8a8f6f..533eaf04f12f 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. + + 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 2ee28266fd07..9e8e004bb1c3 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -36,6 +36,77 @@ 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 +270,8 @@ static void vhost_vq_reset(struct vhost_dev *dev, vq->call = NULL; vq->log_ctx = NULL; vq->memory = NULL; + vq->is_le = virtio_legacy_is_little_endian(); + vhost_vq_reset_user_be(vq); } static int vhost_worker(void *data) @@ -806,6 +879,12 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp) } else filep = eventfp; break; + case VHOST_SET_VRING_ENDIAN: + r = vhost_set_vring_endian(vq, argp); + break; + case VHOST_GET_VRING_ENDIAN: + r = vhost_get_vring_endian(vq, idx, argp); + break; default: r = -ENOIOCTLCMD; } @@ -1044,8 +1123,12 @@ int vhost_init_used(struct vhost_virtqueue *vq) { __virtio16 last_used_idx; int r; - if (!vq->private_data) + if (!vq->private_data) { + vq->is_le = virtio_legacy_is_little_endian(); 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 a4fa33a79bf2..ce6f6da4b09f 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -106,6 +106,14 @@ struct vhost_virtqueue { /* Log write descriptors */ void __user *log_base; struct vhost_log *log; + + /* Ring endianness. Defaults to legacy native endianness. + * Set to true when starting a modern virtio device. */ + bool is_le; +#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY + /* Ring endianness requested by userspace for cross-endian support. */ + bool user_be; +#endif }; struct vhost_dev { @@ -175,8 +183,7 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit) static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq) { - return vhost_has_feature(vq, VIRTIO_F_VERSION_1) || - virtio_legacy_is_little_endian(); + return vq->is_le; } /* Memory accessors */ diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h index bb6a5b4cb3c5..ab3731917bac 100644 --- a/include/uapi/linux/vhost.h +++ b/include/uapi/linux/vhost.h @@ -103,6 +103,20 @@ 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). + * The byte order cannot be changed while the device is active: trying to do so + * returns -EBUSY. + * This is a legacy only API that is simply ignored when VIRTIO_F_VERSION_1 is + * set. + * Not all kernel configurations support this ioctl, but all configurations that + * support SET also support GET. + */ +#define VHOST_VRING_LITTLE_ENDIAN 0 +#define VHOST_VRING_BIG_ENDIAN 1 +#define VHOST_SET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x13, struct vhost_vring_state) +#define VHOST_GET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x14, struct vhost_vring_state) + /* The following ioctls use eventfd file descriptors to signal and poll * for events. */ |