linux-kernel - Re: [RFC v2 1/4] vduse: Add function to get/free the pages for reconnection

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Message-ID: <CACLfguUu83eYPr=yaSMEAm77igOvdc1ZF-LPNPRcbKrg1OsbUA@mail.gmail.com>
Date:   Thu, 21 Sep 2023 22:06:16 +0800
From:   Cindy Lu <lulu@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, maxime.coquelin@...hat.com,
        xieyongji@...edance.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [RFC v2 1/4] vduse: Add function to get/free the pages for reconnection

On Mon, Sep 18, 2023 at 4:41 PM Jason Wang <jasowang@...hat.com> wrote:
>
> On Tue, Sep 12, 2023 at 11:00 AM Cindy Lu <lulu@...hat.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.
>
> Please explain why this is needed instead of only describing how it is
> implemented. (Code can explain itself).
>
> >
> > Signed-off-by: Cindy Lu <lulu@...hat.com>
> > ---
> >  drivers/vdpa/vdpa_user/vduse_dev.c | 86 ++++++++++++++++++++++++++++++
> >  1 file changed, 86 insertions(+)
> >
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index 26b7e29cb900..4c256fa31fc4 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
> > +
> >  #include "iova_domain.h"
> >
> >  #define DRV_AUTHOR   "Yongji Xie <xieyongji@...edance.com>"
> > @@ -41,6 +45,23 @@
> >  #define VDUSE_IOVA_SIZE (128 * 1024 * 1024)
> >  #define VDUSE_MSG_DEFAULT_TIMEOUT 30
> >
> > +/* struct vdpa_reconnect_info save the page information for reconnection
> > + * kernel will init these information while alloc the pages
> > + * and use these information to free the pages
> > + */
> > +struct vdpa_reconnect_info {
> > +       /* Offset (within vm_file) in PAGE_SIZE,
> > +        * this just for check, not using
> > +        */
> > +       u32 index;
> > +       /* physical address for this page*/
> > +       phys_addr_t addr;
> > +       /* virtual address for this page*/
> > +       unsigned long vaddr;
>
> If it could be switched by virt_to_phys() why duplicate those fields?
>
yes will remove this part
Thanks
Cindy
> > +       /* memory size, here always page_size*/
> > +       phys_addr_t size;
>
> If it's always PAGE_SIZE why would we have this?
will remove this
Thanks
Cindy
>
> > +};
> > +
> >  struct vduse_virtqueue {
> >         u16 index;
> >         u16 num_max;
> > @@ -57,6 +78,7 @@ 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 +128,7 @@ 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 +1053,65 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev,
> >         return ret;
> >  }
> >
> > +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 information
> > +        *needed in reconnection,kernel don't need to maintain this
> > +        */
> > +       info = &dev->reconnect_status;
> > +       addr = (void *)get_zeroed_page(GFP_KERNEL);
> > +       if (!addr)
> > +               return -1;
>
> -ENOMEM?
>
sure will change this
Thanks
Cidny
> Thanks
>