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From:   Cindy Lu <lulu@redhat.com>
Date:   Tue, 7 Nov 2023 15:26:27 +0800
Message-ID: <CACLfguU7+Lx_qM-8DePdja63mW2MZC1fhVf0zP=7yzx_+Wehpw@mail.gmail.com>
Subject: Re: [PATCH v1 1/4] vduse: Add function to get/free the pages for reconnection
To:     Jason Wang <jasowang@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 18, 2023 at 10:57=E2=80=AFAM Jason Wang <jasowang@redhat.com> w=
rote:
>
> 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_use=
r/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?
>
sure=EF=BC=8C will remove this here
Thanks
Cindy
> > +};
> > +
> >  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 *=
dev,
> >         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 i=
nformation
> > +        *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.
>
will change this
> > +       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.
>
will change this

> > +       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_conf=
ig *config,
> >                 ret =3D PTR_ERR(dev->dev);
> >                 goto err_dev;
> >         }
> > +
> > +       vduse_alloc_reconnnect_info_mem(dev);
>
> The errors were ignored here.
>
> Thanks
>
sure will add the check here

Thanks
cindy

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