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References: <20231011064208.2143245-1-lulu@redhat.com> <20231011064208.2143245-2-lulu@redhat.com>
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From:   Jason Wang <jasowang@redhat.com>
Date:   Wed, 18 Oct 2023 10:56:43 +0800
Message-ID: <CACGkMEupWg6v2Kp1QFDE1qsc4SeZ220jo0XJ=07h5HJPLSC_Qw@mail.gmail.com>
Subject: Re: [PATCH v1 1/4] vduse: Add function to get/free the pages for reconnection
To:     Cindy Lu <lulu@redhat.com>
Cc:     mst@redhat.com, xieyongji@bytedance.com,
        linux-kernel@vger.kernel.org, maxime.coquelin@redhat.com
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On Wed, Oct 11, 2023 at 2:42=E2=80=AFPM Cindy Lu <lulu@redhat.com> wrote:
>
> Add the function vduse_alloc_reconnnect_info_mem
> and vduse_alloc_reconnnect_info_mem
> In this 2 function, vduse will get/free (vq_num + 1)*page
> Page 0 will be used to save the reconnection information, The
> Userspace App will maintain this. Page 1 ~ vq_num + 1 will save
> the reconnection information for vqs.

I'd align this with the spec. E.g spec starts virtqueue index from 0.

>
> Signed-off-by: Cindy Lu <lulu@redhat.com>
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 78 ++++++++++++++++++++++++++++++
>  1 file changed, 78 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/=
vduse_dev.c
> index 26b7e29cb900..565126a9ab01 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -30,6 +30,10 @@
>  #include <uapi/linux/virtio_blk.h>
>  #include <linux/mod_devicetable.h>
>
> +#ifdef CONFIG_X86
> +#include <asm/set_memory.h>
> +#endif

Why do we need special care for x86?

> +
>  #include "iova_domain.h"
>
>  #define DRV_AUTHOR   "Yongji Xie <xieyongji@bytedance.com>"
> @@ -41,6 +45,19 @@
>  #define VDUSE_IOVA_SIZE (128 * 1024 * 1024)
>  #define VDUSE_MSG_DEFAULT_TIMEOUT 30
>
> +/* struct vdpa_reconnect_info saved the alloc pages info
> + * these pages will mmaped to userspace for reconnection
> + */
> +struct vdpa_reconnect_info {
> +       /* Offset (within vm_file) in PAGE_SIZE
> +        */
> +       u32 index;
> +       /* virtual address for this page*/
> +       unsigned long vaddr;
> +       /* allocated memory size, */
> +       phys_addr_t size;

Anything wrong with using "unsigned long" here.

Btw, what is "allocated memory size" since I think we can use up to
PAGE_SIZE here?

> +};
> +
>  struct vduse_virtqueue {
>         u16 index;
>         u16 num_max;
> @@ -57,6 +74,7 @@ struct vduse_virtqueue {
>         struct vdpa_callback cb;
>         struct work_struct inject;
>         struct work_struct kick;
> +       struct vdpa_reconnect_info reconnect_info;
>  };
>
>  struct vduse_dev;
> @@ -106,6 +124,7 @@ struct vduse_dev {
>         u32 vq_align;
>         struct vduse_umem *umem;
>         struct mutex mem_lock;
> +       struct vdpa_reconnect_info reconnect_status;
>  };
>
>  struct vduse_dev_msg {
> @@ -1030,6 +1049,61 @@ static int vduse_dev_reg_umem(struct vduse_dev *de=
v,
>         return ret;
>  }
>
> +static int vduse_alloc_reconnnect_info_mem(struct vduse_dev *dev)
> +{
> +       struct vdpa_reconnect_info *info;
> +       struct vduse_virtqueue *vq;
> +       void *addr;
> +
> +       /*page 0 is use to save status,dpdk will use this to save the inf=
ormation
> +        *needed in reconnection,kernel don't need to maintain this
> +        */

Let's avoid mentioning any specific userspace like DPDK in the kernel
source. A good uAPI should not be designed for a specific userspace.

> +       info =3D &dev->reconnect_status;
> +       addr =3D (void *)get_zeroed_page(GFP_KERNEL);
> +       if (!addr)
> +               return -1;

Let's don't use magic number here but something like -ENOMEM.

> +
> +       info->vaddr =3D (unsigned long)(addr);
> +       info->size =3D PAGE_SIZE;
> +       /* index is vm Offset in PAGE_SIZE */
> +       info->index =3D 0;
> +
> +       /*page 1~ vq_num + 1 save the reconnect info for vqs*/

There's no need to explain what the code does.

> +       for (int i =3D 0; i < dev->vq_num + 1; i++) {
> +               vq =3D &dev->vqs[i];
> +               info =3D &vq->reconnect_info;
> +               addr =3D (void *)get_zeroed_page(GFP_KERNEL);
> +               if (!addr)
> +                       return -1;
> +
> +               info->vaddr =3D (unsigned long)(addr);
> +               info->size =3D PAGE_SIZE;
> +               info->index =3D i + 1;

Btw, I don't see an obvious difference in the page for virtqueue and
device. Could we unify the logic there? So did the free.

> +       }
> +
> +       return 0;
> +}
> +
> +static int vduse_free_reconnnect_info_mem(struct vduse_dev *dev)
> +{
> +       struct vdpa_reconnect_info *info;
> +       struct vduse_virtqueue *vq;
> +
> +       info =3D &dev->reconnect_status;
> +       free_page(info->vaddr);
> +       info->size =3D 0;
> +       info->vaddr =3D 0;
> +       for (int i =3D 0; i < dev->vq_num + 1; i++) {
> +               vq =3D &dev->vqs[i];
> +               info =3D &vq->reconnect_info;
> +               free_page(info->vaddr);
> +               info->size =3D 0;
> +               info->vaddr =3D 0;
> +       }
> +
> +       return 0;
> +}
> +
>  static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
>                             unsigned long arg)
>  {
> @@ -1390,6 +1464,8 @@ static int vduse_destroy_dev(char *name)
>                 mutex_unlock(&dev->lock);
>                 return -EBUSY;
>         }
> +       vduse_free_reconnnect_info_mem(dev);
> +
>         dev->connected =3D true;
>         mutex_unlock(&dev->lock);
>
> @@ -1542,6 +1618,8 @@ static int vduse_create_dev(struct vduse_dev_config=
 *config,
>                 ret =3D PTR_ERR(dev->dev);
>                 goto err_dev;
>         }
> +
> +       vduse_alloc_reconnnect_info_mem(dev);

The errors were ignored here.

Thanks

>         __module_get(THIS_MODULE);
>
>         return 0;
> --
> 2.34.3
>