linux-kernel - Re: [PATCH v4 5/5] vduse: Support querying information of IOVA regions

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Message-ID: <CACGkMEuN0zqyLQ6vD7MvjAhtJVvmMhsn_T4b5ww0vviwq5hBrg@mail.gmail.com>
Date:   Thu, 28 Jul 2022 13:57:48 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xie Yongji <xieyongji@...edance.com>
Cc:     mst <mst@...hat.com>, Liu Xiaodong <xiaodong.liu@...el.com>,
        Maxime Coquelin <maxime.coquelin@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        songmuchun@...edance.com,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 5/5] vduse: Support querying information of IOVA regions

On Thu, Jul 28, 2022 at 11:20 AM Xie Yongji <xieyongji@...edance.com> wrote:
>
> This introduces a new ioctl: VDUSE_IOTLB_GET_INFO to
> support querying some information of IOVA regions.
>
> Now it can be used to query whether the IOVA region
> supports userspace memory registration.
>
> Signed-off-by: Xie Yongji <xieyongji@...edance.com>
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 39 ++++++++++++++++++++++++++++++
>  include/uapi/linux/vduse.h         | 24 ++++++++++++++++++
>  2 files changed, 63 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index eedff0a3885a..e820c37dcba8 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1228,6 +1228,45 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
>                                            umem.size);
>                 break;
>         }
> +       case VDUSE_IOTLB_GET_INFO: {
> +               struct vduse_iova_info info;
> +               struct vhost_iotlb_map *map;
> +               struct vduse_iova_domain *domain = dev->domain;
> +
> +               ret = -EFAULT;
> +               if (copy_from_user(&info, argp, sizeof(info)))
> +                       break;
> +
> +               ret = -EINVAL;
> +               if (info.start > info.last)
> +                       break;
> +
> +               if (!is_mem_zero((const char *)info.reserved,
> +                                sizeof(info.reserved)))
> +                       break;
> +
> +               spin_lock(&domain->iotlb_lock);
> +               map = vhost_iotlb_itree_first(domain->iotlb,
> +                                             info.start, info.last);
> +               if (map) {
> +                       info.start = map->start;
> +                       info.last = map->last;
> +                       info.capability = 0;
> +                       if (domain->bounce_map && map->start >= 0 &&
> +                           map->last < domain->bounce_size)
> +                               info.capability |= VDUSE_IOVA_CAP_UMEM;
> +               }
> +               spin_unlock(&domain->iotlb_lock);
> +               if (!map)
> +                       break;
> +
> +               ret = -EFAULT;
> +               if (copy_to_user(argp, &info, sizeof(info)))
> +                       break;
> +
> +               ret = 0;
> +               break;
> +       }
>         default:
>                 ret = -ENOIOCTLCMD;
>                 break;
> diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> index 9885e0571f09..11bd48c72c6c 100644
> --- a/include/uapi/linux/vduse.h
> +++ b/include/uapi/linux/vduse.h
> @@ -233,6 +233,30 @@ struct vduse_iova_umem {
>  /* De-register the userspace memory. Caller should set iova and size field. */
>  #define VDUSE_IOTLB_DEREG_UMEM _IOW(VDUSE_BASE, 0x19, struct vduse_iova_umem)
>
> +/**
> + * struct vduse_iova_info - information of one IOVA region
> + * @start: start of the IOVA region
> + * @last: last of the IOVA region
> + * @capability: capability of the IOVA regsion
> + * @reserved: for future use, needs to be initialized to zero
> + *
> + * Structure used by VDUSE_IOTLB_GET_INFO ioctl to get information of
> + * one IOVA region.
> + */
> +struct vduse_iova_info {
> +       __u64 start;
> +       __u64 last;
> +#define VDUSE_IOVA_CAP_UMEM (1 << 0)
> +       __u64 capability;
> +       __u64 reserved[3];
> +};
> +
> +/*
> + * Find the first IOVA region that overlaps with the range [start, last]

So the code is actually find the IOVA region that is the super range
of [start, last] instead of overlap:


> +                       if (domain->bounce_map && map->start >= 0 &&
> +                           map->last < domain->bounce_size)
> +                               info.capability |= VDUSE_IOVA_CAP_UMEM;

Which part is wrong?

Thanks

> + * and return some information on it. Caller should set start and last fields.
> + */
> +#define VDUSE_IOTLB_GET_INFO   _IOWR(VDUSE_BASE, 0x1a, struct vduse_iova_info)
> +
>  /* The control messages definition for read(2)/write(2) on /dev/vduse/$NAME */
>
>  /**
> --
> 2.20.1
>