linux-kernel - Re: [PATCH] vdpa_sim_blk: add support for VIRTIO_BLK_T

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Date:   Fri, 29 Apr 2022 10:46:40 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Max Gurtovoy <mgurtovoy@...dia.com>
Subject: Re: [PATCH] vdpa_sim_blk: add support for VIRTIO_BLK_T_FLUSH

On Thu, Apr 28, 2022 at 11:13 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
>
> The simulator behaves like a ramdisk, so we don't have to do
> anything when a VIRTIO_BLK_T_FLUSH request is received, but it
> could be useful to test driver behavior.
>
> Let's expose the VIRTIO_BLK_F_FLUSH feature to inform the driver
> that we support the flush command.
>
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> ---
>  drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> index 42d401d43911..a6dd1233797c 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> @@ -25,6 +25,7 @@
>  #define DRV_LICENSE  "GPL v2"
>
>  #define VDPASIM_BLK_FEATURES   (VDPASIM_FEATURES | \
> +                                (1ULL << VIRTIO_BLK_F_FLUSH)    | \
>                                  (1ULL << VIRTIO_BLK_F_SIZE_MAX) | \
>                                  (1ULL << VIRTIO_BLK_F_SEG_MAX)  | \
>                                  (1ULL << VIRTIO_BLK_F_BLK_SIZE) | \
> @@ -166,6 +167,17 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim,
>                 pushed += bytes;
>                 break;
>
> +       case VIRTIO_BLK_T_FLUSH:
> +               if (sector != 0) {
> +                       dev_err(&vdpasim->vdpa.dev,
> +                               "A driver MUST set sector to 0 for a VIRTIO_BLK_T_FLUSH request - sector: 0x%llx\n",
> +                               sector);

If this is something that could be triggered by userspace/guest, then
we should avoid this.

Thanks

> +                       status = VIRTIO_BLK_S_IOERR;
> +                       break;
> +               }
> +
> +               break;
> +
>         default:
>                 dev_warn(&vdpasim->vdpa.dev,
>                          "Unsupported request type %d\n", type);
> --
> 2.35.1
>