Re: [PATCH v3 4/8] vringh: support VA with iotlb

Stefano Garzarella
2023-03-23T10:41:31Z

On Thu, Mar 23, 2023 at 11:36:28AM +0800, Jason Wang wrote:
>On Tue, Mar 21, 2023 at 11:43 PM Stefano Garzarella <sgarzare@redhat.com> 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.
>>
>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>> ---
>>
>> Notes:
>> 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 | 5 +-
>> drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>> drivers/vdpa/vdpa_sim/vdpa_sim.c | 4 +-
>> drivers/vhost/vringh.c | 153 +++++++++++++++++++++++-------
>> 4 files changed, 127 insertions(+), 37 deletions(-)
>>
>> diff --git a/include/linux/vringh.h b/include/linux/vringh.h
>> index 1991a02c6431..d39b9f2dcba0 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;
>>
>> @@ -279,7 +282,7 @@ void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb,
>> spinlock_t *iotlb_lock);
>>
>> int vringh_init_iotlb(struct vringh *vrh, u64 features,
>> - unsigned int num, bool weak_barriers,
>> + unsigned int num, bool weak_barriers, bool use_va,
>> struct vring_desc *desc,
>> struct vring_avail *avail,
>> struct vring_used *used);
>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> index 520646ae7fa0..dfd0e000217b 100644
>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> @@ -2537,7 +2537,7 @@ static int setup_cvq_vring(struct mlx5_vdpa_dev *mvdev)
>>
>> if (mvdev->actual_features & BIT_ULL(VIRTIO_NET_F_CTRL_VQ))
>> err = vringh_init_iotlb(&cvq->vring, mvdev->actual_features,
>> - MLX5_CVQ_MAX_ENT, false,
>> + MLX5_CVQ_MAX_ENT, false, false,
>
>To avoid those changes, would it be better to introduce
>vringh_init_iotlb_va() so vringh_init_iotlb() can stick to pa.

Okay, I don't have a strong opinion, I'll add vringh_init_iotlb_va().

>
>> (struct vring_desc *)(uintptr_t)cvq->desc_addr,
>> (struct vring_avail *)(uintptr_t)cvq->driver_addr,
>> (struct vring_used *)(uintptr_t)cvq->device_addr);
>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> index eea23c630f7c..47cdf2a1f5b8 100644
>> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> @@ -60,7 +60,7 @@ static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx)
>> struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
>> uint16_t last_avail_idx = vq->vring.last_avail_idx;
>>
>> - vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num, true,
>> + vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num, true, false,
>> (struct vring_desc *)(uintptr_t)vq->desc_addr,
>> (struct vring_avail *)
>> (uintptr_t)vq->driver_addr,
>> @@ -92,7 +92,7 @@ static void vdpasim_vq_reset(struct vdpasim *vdpasim,
>> vq->cb = NULL;
>> vq->private = NULL;
>> vringh_init_iotlb(&vq->vring, vdpasim->dev_attr.supported_features,
>> - VDPASIM_QUEUE_MAX, false, NULL, NULL, NULL);
>> + VDPASIM_QUEUE_MAX, false, false, NULL, NULL, NULL);
>>
>> vq->vring.notify = NULL;
>> }
>> diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
>> index 0ba3ef809e48..72c88519329a 100644
>> --- a/drivers/vhost/vringh.c
>> +++ b/drivers/vhost/vringh.c
>> @@ -1094,10 +1094,18 @@ 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;
>> + bool is_iovec;
>
>I wonder if this is needed (if vringh is passed to every iotlb_vec helper).

Yep, I can use vringh->use_va.

>
>> +};
>> +
>> 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 +1115,9 @@ static int iotlb_translate(const struct vringh *vrh,
>> spin_lock(vrh->iotlb_lock);
>>
>> while (len > s) {
>> - u64 size, pa, pfn;
>> + u64 size;
>>
>> - if (unlikely(ret >= iov_size)) {
>> + if (unlikely(ret >= ivec->count)) {
>> ret = -ENOBUFS;
>> break;
>> }
>> @@ -1124,10 +1132,22 @@ 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));
>> + if (ivec->is_iovec) {
>> + struct iovec *iovec = ivec->iov.iovec;
>> +
>> + iovec[ret].iov_len = min(len - s, size);
>> + iovec[ret].iov_base = (void __user *)(unsigned long)
>> + (map->addr + addr - map->start);
>
>map->addr - map->start to avoid overflow?

Right, it was pre-existing, but I'll fix since I'm here (also in the
else branch).
And since it's duplicate code, I'll declare it outside!

>
>> + } else {
>> + u64 pa = map->addr + addr - map->start;
>> + u64 pfn = pa >> PAGE_SHIFT;
>> + struct bio_vec *bvec = ivec->iov.bvec;
>> +
>> + bvec_set_page(&bvec[ret], pfn_to_page(pfn),
>> + min(len - s, size),
>> + pa & (PAGE_SIZE - 1));
>> + }
>> +
>> s += size;
>> addr += size;
>> ++ret;
>> @@ -1141,26 +1161,42 @@ static int iotlb_translate(const struct vringh *vrh,
>> return ret;
>> }
>>
>> +#define IOTLB_IOV_SIZE 16
>> +
>> 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_SIZE];
>> + struct bio_vec bvec[IOTLB_IOV_SIZE];
>> + } iov;
>> u64 total_translated = 0;
>>
>> + ivec.iov.iovec = iov.iovec;
>
>ivc.iov = iov ?

I tried, but they are both anonymous unions, so I cannot assign them.

Also, this inner union I need to allocate space in the stack to hold
both arrays, while the union in iotlb_vec to carry both pointers.

I don't know whether to add a third field (e.g. `void *raw`) to both and
assign it.

>
>Others look good.

Thanks,
Stefano