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Date: Wed, 21 Dec 2022 08:17:41 +0100
From: Eugenio Perez Martin <eperezma@...hat.com>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: virtualization@...ts.linux-foundation.org,
Jason Wang <jasowang@...hat.com>,
Andrey Zhadchenko <andrey.zhadchenko@...tuozzo.com>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
"Michael S. Tsirkin" <mst@...hat.com>, stefanha@...hat.com,
netdev@...r.kernel.org
Subject: Re: [RFC PATCH 6/6] vdpa_sim: add support for user VA
On Wed, Dec 14, 2022 at 5:31 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
>
> The new "use_va" module parameter (default: false) is used in
Why not true by default? I'd say it makes more sense for the simulator
to use va mode and only use pa for testing it.
> vdpa_alloc_device() to inform the vDPA framework that the device
> supports VA.
>
> vringh is initialized to use VA only when "use_va" is true and the
> user's mm has been bound. So, only when the bus supports user VA
> (e.g. vhost-vdpa).
>
> vdpasim_mm_work_fn work is used to attach the kthread to the user
> address space when the .bind_mm callback is invoked, and to detach
> it when the device is reset.
>
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> ---
> drivers/vdpa/vdpa_sim/vdpa_sim.h | 1 +
> drivers/vdpa/vdpa_sim/vdpa_sim.c | 104 ++++++++++++++++++++++++++++++-
> 2 files changed, 103 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> index 07ef53ea375e..1b010e5c0445 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> @@ -55,6 +55,7 @@ struct vdpasim {
> struct vdpasim_virtqueue *vqs;
> struct kthread_worker *worker;
> struct kthread_work work;
> + struct mm_struct *mm_bound;
> struct vdpasim_dev_attr dev_attr;
> /* spinlock to synchronize virtqueue state */
> spinlock_t lock;
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index 36a1d2e0a6ba..6e07cedef30c 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> @@ -36,10 +36,90 @@ module_param(max_iotlb_entries, int, 0444);
> MODULE_PARM_DESC(max_iotlb_entries,
> "Maximum number of iotlb entries for each address space. 0 means unlimited. (default: 2048)");
>
> +static bool use_va;
> +module_param(use_va, bool, 0444);
> +MODULE_PARM_DESC(use_va, "Enable the device's ability to use VA");
> +
> #define VDPASIM_QUEUE_ALIGN PAGE_SIZE
> #define VDPASIM_QUEUE_MAX 256
> #define VDPASIM_VENDOR_ID 0
>
> +struct vdpasim_mm_work {
> + struct kthread_work work;
> + struct task_struct *owner;
> + struct mm_struct *mm;
> + bool bind;
> + int ret;
> +};
> +
> +static void vdpasim_mm_work_fn(struct kthread_work *work)
> +{
> + struct vdpasim_mm_work *mm_work =
> + container_of(work, struct vdpasim_mm_work, work);
> +
> + mm_work->ret = 0;
> +
> + if (mm_work->bind) {
> + kthread_use_mm(mm_work->mm);
> +#if 0
> + if (mm_work->owner)
> + mm_work->ret = cgroup_attach_task_all(mm_work->owner,
> + current);
> +#endif
> + } else {
> +#if 0
> + //TODO: check it
> + cgroup_release(current);
> +#endif
> + kthread_unuse_mm(mm_work->mm);
> + }
> +}
> +
> +static void vdpasim_worker_queue_mm(struct vdpasim *vdpasim,
> + struct vdpasim_mm_work *mm_work)
> +{
> + struct kthread_work *work = &mm_work->work;
> +
> + kthread_init_work(work, vdpasim_mm_work_fn);
> + kthread_queue_work(vdpasim->worker, work);
> +
> + spin_unlock(&vdpasim->lock);
> + kthread_flush_work(work);
> + spin_lock(&vdpasim->lock);
> +}
> +
> +static int vdpasim_worker_bind_mm(struct vdpasim *vdpasim,
> + struct mm_struct *new_mm,
> + struct task_struct *owner)
> +{
> + struct vdpasim_mm_work mm_work;
> +
> + mm_work.owner = owner;
> + mm_work.mm = new_mm;
> + mm_work.bind = true;
> +
> + vdpasim_worker_queue_mm(vdpasim, &mm_work);
> +
> + if (!mm_work.ret)
> + vdpasim->mm_bound = new_mm;
> +
> + return mm_work.ret;
> +}
> +
> +static void vdpasim_worker_unbind_mm(struct vdpasim *vdpasim)
> +{
> + struct vdpasim_mm_work mm_work;
> +
> + if (!vdpasim->mm_bound)
> + return;
> +
> + mm_work.mm = vdpasim->mm_bound;
> + mm_work.bind = false;
> +
> + vdpasim_worker_queue_mm(vdpasim, &mm_work);
> +
> + vdpasim->mm_bound = NULL;
> +}
> static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa)
> {
> return container_of(vdpa, struct vdpasim, vdpa);
> @@ -66,8 +146,10 @@ static void vdpasim_vq_notify(struct vringh *vring)
> static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx)
> {
> struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
> + bool va_enabled = use_va && vdpasim->mm_bound;
>
> - vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num, false, false,
> + vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num, false,
> + va_enabled,
> (struct vring_desc *)(uintptr_t)vq->desc_addr,
> (struct vring_avail *)
> (uintptr_t)vq->driver_addr,
> @@ -96,6 +178,9 @@ static void vdpasim_do_reset(struct vdpasim *vdpasim)
> {
> int i;
>
> + //TODO: should we cancel the works?
> + vdpasim_worker_unbind_mm(vdpasim);
> +
> spin_lock(&vdpasim->iommu_lock);
>
> for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {
> @@ -275,7 +360,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
>
> vdpasim = vdpa_alloc_device(struct vdpasim, vdpa, NULL, ops,
> dev_attr->ngroups, dev_attr->nas,
> - dev_attr->name, false);
> + dev_attr->name, use_va);
> if (IS_ERR(vdpasim)) {
> ret = PTR_ERR(vdpasim);
> goto err_alloc;
> @@ -657,6 +742,19 @@ static int vdpasim_set_map(struct vdpa_device *vdpa, unsigned int asid,
> return ret;
> }
>
> +static int vdpasim_bind_mm(struct vdpa_device *vdpa, struct mm_struct *mm,
> + struct task_struct *owner)
> +{
> + struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> + int ret;
> +
> + spin_lock(&vdpasim->lock);
> + ret = vdpasim_worker_bind_mm(vdpasim, mm, owner);
> + spin_unlock(&vdpasim->lock);
> +
> + return ret;
> +}
> +
> static int vdpasim_dma_map(struct vdpa_device *vdpa, unsigned int asid,
> u64 iova, u64 size,
> u64 pa, u32 perm, void *opaque)
> @@ -744,6 +842,7 @@ static const struct vdpa_config_ops vdpasim_config_ops = {
> .set_group_asid = vdpasim_set_group_asid,
> .dma_map = vdpasim_dma_map,
> .dma_unmap = vdpasim_dma_unmap,
> + .bind_mm = vdpasim_bind_mm,
> .free = vdpasim_free,
> };
>
> @@ -776,6 +875,7 @@ static const struct vdpa_config_ops vdpasim_batch_config_ops = {
> .get_iova_range = vdpasim_get_iova_range,
> .set_group_asid = vdpasim_set_group_asid,
> .set_map = vdpasim_set_map,
> + .bind_mm = vdpasim_bind_mm,
> .free = vdpasim_free,
> };
>
> --
> 2.38.1
>
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