Re: [PATCH v5 5/9] vringh: support VA with iotlb

From: Jason Wang
Date: Tue Apr 11 2023 - 01:42:53 EST

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On Tue, Apr 4, 2023 at 9:17 PM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:
>
> vDPA supports the possibility to use user VA in the iotlb messages.
> So, let's add support for user VA in vringh to use it in the vDPA
> simulators.
>
> Acked-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>

Acked-by: Jason Wang <jasowang@xxxxxxxxxx>

Thanks

> ---
>
> Notes:
> v5:
> - s/userpace/userspace/ in the vringh_init_iotlb_va doc [Simon]
> v4:
> - used uintptr_t for `io_addr` [Eugenio]
> - added `io_addr` and `io_len` variables in iotlb_translate
> - avoided overflow doing `map->addr - map->start + addr` [Jason]
> - removed `is_iovec` field from struct iotlb_vec [Jason]
> - added vringh_init_iotlb_va() [Jason]
> v3:
> - refactored avoiding code duplication [Eugenio]
> v2:
> - replace kmap_atomic() with kmap_local_page() [see previous patch]
> - fix cast warnings when build with W=1 C=1
>
> include/linux/vringh.h | 9 +++
> drivers/vhost/vringh.c | 171 +++++++++++++++++++++++++++++++++--------
> 2 files changed, 148 insertions(+), 32 deletions(-)
>
> diff --git a/include/linux/vringh.h b/include/linux/vringh.h
> index 1991a02c6431..b4edfadf5479 100644
> --- a/include/linux/vringh.h
> +++ b/include/linux/vringh.h
> @@ -32,6 +32,9 @@ struct vringh {
> /* Can we get away with weak barriers? */
> bool weak_barriers;
>
> + /* Use user's VA */
> + bool use_va;
> +
> /* Last available index we saw (ie. where we're up to). */
> u16 last_avail_idx;
>
> @@ -284,6 +287,12 @@ int vringh_init_iotlb(struct vringh *vrh, u64 features,
> struct vring_avail *avail,
> struct vring_used *used);
>
> +int vringh_init_iotlb_va(struct vringh *vrh, u64 features,
> + unsigned int num, bool weak_barriers,
> + struct vring_desc *desc,
> + struct vring_avail *avail,
> + struct vring_used *used);
> +
> int vringh_getdesc_iotlb(struct vringh *vrh,
> struct vringh_kiov *riov,
> struct vringh_kiov *wiov,
> diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
> index 4aee230f7622..ab95160dcdd9 100644
> --- a/drivers/vhost/vringh.c
> +++ b/drivers/vhost/vringh.c
> @@ -1094,10 +1094,17 @@ EXPORT_SYMBOL(vringh_need_notify_kern);
>
> #if IS_REACHABLE(CONFIG_VHOST_IOTLB)
>
> +struct iotlb_vec {
> + union {
> + struct iovec *iovec;
> + struct bio_vec *bvec;
> + } iov;
> + size_t count;
> +};
> +
> static int iotlb_translate(const struct vringh *vrh,
> u64 addr, u64 len, u64 *translated,
> - struct bio_vec iov[],
> - int iov_size, u32 perm)
> + struct iotlb_vec *ivec, u32 perm)
> {
> struct vhost_iotlb_map *map;
> struct vhost_iotlb *iotlb = vrh->iotlb;
> @@ -1107,9 +1114,11 @@ static int iotlb_translate(const struct vringh *vrh,
> spin_lock(vrh->iotlb_lock);
>
> while (len > s) {
> - u64 size, pa, pfn;
> + uintptr_t io_addr;
> + size_t io_len;
> + u64 size;
>
> - if (unlikely(ret >= iov_size)) {
> + if (unlikely(ret >= ivec->count)) {
> ret = -ENOBUFS;
> break;
> }
> @@ -1124,10 +1133,22 @@ static int iotlb_translate(const struct vringh *vrh,
> }
>
> size = map->size - addr + map->start;
> - pa = map->addr + addr - map->start;
> - pfn = pa >> PAGE_SHIFT;
> - bvec_set_page(&iov[ret], pfn_to_page(pfn), min(len - s, size),
> - pa & (PAGE_SIZE - 1));
> + io_len = min(len - s, size);
> + io_addr = map->addr - map->start + addr;
> +
> + if (vrh->use_va) {
> + struct iovec *iovec = ivec->iov.iovec;
> +
> + iovec[ret].iov_len = io_len;
> + iovec[ret].iov_base = (void __user *)io_addr;
> + } else {
> + u64 pfn = io_addr >> PAGE_SHIFT;
> + struct bio_vec *bvec = ivec->iov.bvec;
> +
> + bvec_set_page(&bvec[ret], pfn_to_page(pfn), io_len,
> + io_addr & (PAGE_SIZE - 1));
> + }
> +
> s += size;
> addr += size;
> ++ret;
> @@ -1146,23 +1167,36 @@ static int iotlb_translate(const struct vringh *vrh,
> static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
> void *src, size_t len)
> {
> + struct iotlb_vec ivec;
> + union {
> + struct iovec iovec[IOTLB_IOV_STRIDE];
> + struct bio_vec bvec[IOTLB_IOV_STRIDE];
> + } iov;
> u64 total_translated = 0;
>
> + ivec.iov.iovec = iov.iovec;
> + ivec.count = IOTLB_IOV_STRIDE;
> +
> while (total_translated < len) {
> - struct bio_vec iov[IOTLB_IOV_STRIDE];
> struct iov_iter iter;
> u64 translated;
> int ret;
>
> ret = iotlb_translate(vrh, (u64)(uintptr_t)src,
> len - total_translated, &translated,
> - iov, ARRAY_SIZE(iov), VHOST_MAP_RO);
> + &ivec, VHOST_MAP_RO);
> if (ret == -ENOBUFS)
> - ret = ARRAY_SIZE(iov);
> + ret = IOTLB_IOV_STRIDE;
> else if (ret < 0)
> return ret;
>
> - iov_iter_bvec(&iter, ITER_SOURCE, iov, ret, translated);
> + if (vrh->use_va) {
> + iov_iter_init(&iter, ITER_SOURCE, ivec.iov.iovec, ret,
> + translated);
> + } else {
> + iov_iter_bvec(&iter, ITER_SOURCE, ivec.iov.bvec, ret,
> + translated);
> + }
>
> ret = copy_from_iter(dst, translated, &iter);
> if (ret < 0)
> @@ -1179,23 +1213,36 @@ static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
> static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
> void *src, size_t len)
> {
> + struct iotlb_vec ivec;
> + union {
> + struct iovec iovec[IOTLB_IOV_STRIDE];
> + struct bio_vec bvec[IOTLB_IOV_STRIDE];
> + } iov;
> u64 total_translated = 0;
>
> + ivec.iov.iovec = iov.iovec;
> + ivec.count = IOTLB_IOV_STRIDE;
> +
> while (total_translated < len) {
> - struct bio_vec iov[IOTLB_IOV_STRIDE];
> struct iov_iter iter;
> u64 translated;
> int ret;
>
> ret = iotlb_translate(vrh, (u64)(uintptr_t)dst,
> len - total_translated, &translated,
> - iov, ARRAY_SIZE(iov), VHOST_MAP_WO);
> + &ivec, VHOST_MAP_WO);
> if (ret == -ENOBUFS)
> - ret = ARRAY_SIZE(iov);
> + ret = IOTLB_IOV_STRIDE;
> else if (ret < 0)
> return ret;
>
> - iov_iter_bvec(&iter, ITER_DEST, iov, ret, translated);
> + if (vrh->use_va) {
> + iov_iter_init(&iter, ITER_DEST, ivec.iov.iovec, ret,
> + translated);
> + } else {
> + iov_iter_bvec(&iter, ITER_DEST, ivec.iov.bvec, ret,
> + translated);
> + }
>
> ret = copy_to_iter(src, translated, &iter);
> if (ret < 0)
> @@ -1212,20 +1259,36 @@ static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
> static inline int getu16_iotlb(const struct vringh *vrh,
> u16 *val, const __virtio16 *p)
> {
> - struct bio_vec iov;
> - void *kaddr, *from;
> + struct iotlb_vec ivec;
> + union {
> + struct iovec iovec[1];
> + struct bio_vec bvec[1];
> + } iov;
> + __virtio16 tmp;
> int ret;
>
> + ivec.iov.iovec = iov.iovec;
> + ivec.count = 1;
> +
> /* Atomic read is needed for getu16 */
> - ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p), NULL,
> - &iov, 1, VHOST_MAP_RO);
> + ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
> + NULL, &ivec, VHOST_MAP_RO);
> if (ret < 0)
> return ret;
>
> - kaddr = kmap_local_page(iov.bv_page);
> - from = kaddr + iov.bv_offset;
> - *val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)from));
> - kunmap_local(kaddr);
> + if (vrh->use_va) {
> + ret = __get_user(tmp, (__virtio16 __user *)ivec.iov.iovec[0].iov_base);
> + if (ret)
> + return ret;
> + } else {
> + void *kaddr = kmap_local_page(ivec.iov.bvec[0].bv_page);
> + void *from = kaddr + ivec.iov.bvec[0].bv_offset;
> +
> + tmp = READ_ONCE(*(__virtio16 *)from);
> + kunmap_local(kaddr);
> + }
> +
> + *val = vringh16_to_cpu(vrh, tmp);
>
> return 0;
> }
> @@ -1233,20 +1296,36 @@ static inline int getu16_iotlb(const struct vringh *vrh,
> static inline int putu16_iotlb(const struct vringh *vrh,
> __virtio16 *p, u16 val)
> {
> - struct bio_vec iov;
> - void *kaddr, *to;
> + struct iotlb_vec ivec;
> + union {
> + struct iovec iovec;
> + struct bio_vec bvec;
> + } iov;
> + __virtio16 tmp;
> int ret;
>
> + ivec.iov.iovec = &iov.iovec;
> + ivec.count = 1;
> +
> /* Atomic write is needed for putu16 */
> - ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p), NULL,
> - &iov, 1, VHOST_MAP_WO);
> + ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
> + NULL, &ivec, VHOST_MAP_RO);
> if (ret < 0)
> return ret;
>
> - kaddr = kmap_local_page(iov.bv_page);
> - to = kaddr + iov.bv_offset;
> - WRITE_ONCE(*(__virtio16 *)to, cpu_to_vringh16(vrh, val));
> - kunmap_local(kaddr);
> + tmp = cpu_to_vringh16(vrh, val);
> +
> + if (vrh->use_va) {
> + ret = __put_user(tmp, (__virtio16 __user *)ivec.iov.iovec[0].iov_base);
> + if (ret)
> + return ret;
> + } else {
> + void *kaddr = kmap_local_page(ivec.iov.bvec[0].bv_page);
> + void *to = kaddr + ivec.iov.bvec[0].bv_offset;
> +
> + WRITE_ONCE(*(__virtio16 *)to, tmp);
> + kunmap_local(kaddr);
> + }
>
> return 0;
> }
> @@ -1320,11 +1399,39 @@ int vringh_init_iotlb(struct vringh *vrh, u64 features,
> struct vring_avail *avail,
> struct vring_used *used)
> {
> + vrh->use_va = false;
> +
> return vringh_init_kern(vrh, features, num, weak_barriers,
> desc, avail, used);
> }
> EXPORT_SYMBOL(vringh_init_iotlb);
>
> +/**
> + * vringh_init_iotlb_va - initialize a vringh for a ring with IOTLB containing
> + * user VA.
> + * @vrh: the vringh to initialize.
> + * @features: the feature bits for this ring.
> + * @num: the number of elements.
> + * @weak_barriers: true if we only need memory barriers, not I/O.
> + * @desc: the userspace descriptor pointer.
> + * @avail: the userspace avail pointer.
> + * @used: the userspace used pointer.
> + *
> + * Returns an error if num is invalid.
> + */
> +int vringh_init_iotlb_va(struct vringh *vrh, u64 features,
> + unsigned int num, bool weak_barriers,
> + struct vring_desc *desc,
> + struct vring_avail *avail,
> + struct vring_used *used)
> +{
> + vrh->use_va = true;
> +
> + return vringh_init_kern(vrh, features, num, weak_barriers,
> + desc, avail, used);
> +}
> +EXPORT_SYMBOL(vringh_init_iotlb_va);
> +
> /**
> * vringh_set_iotlb - initialize a vringh for a ring with IOTLB.
> * @vrh: the vring
> --
> 2.39.2
>

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