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

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Date: Mon, 18 Sep 2023 16:41:00 +0800
From: Jason Wang <jasowang@...hat.com>
To: Cindy Lu <lulu@...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 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?

> +       /* memory size, here always page_size*/
> +       phys_addr_t size;

If it's always PAGE_SIZE why would we have this?

> +};
> +
>  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?

Thanks