linux-kernel - Re: [PATCH vhost v4 02/15] vdpa: Add VHOST_BACKEND_F_CHANGEABLE_VQ_ADDR_IN

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Message-ID: <CACGkMEv7xQkZYJAgAUK6C3oUrZ9vuUJdTKRzihXcNPb-iWdpJw@mail.gmail.com>
Date: Wed, 20 Dec 2023 11:46:50 +0800
From: Jason Wang <jasowang@...hat.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Eugenio Perez Martin <eperezma@...hat.com>, 
	Si-Wei Liu <si-wei.liu@...cle.com>, Saeed Mahameed <saeedm@...dia.com>, 
	Leon Romanovsky <leon@...nel.org>, virtualization@...ts.linux-foundation.org, 
	Gal Pressman <gal@...dia.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Parav Pandit <parav@...dia.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH vhost v4 02/15] vdpa: Add VHOST_BACKEND_F_CHANGEABLE_VQ_ADDR_IN_SUSPEND
 flag

On Wed, Dec 20, 2023 at 2:09 AM Dragos Tatulea <dtatulea@...dia.com> wrote:
>
> The virtio spec doesn't allow changing virtqueue addresses after
> DRIVER_OK. Some devices do support this operation when the device is
> suspended. The VHOST_BACKEND_F_CHANGEABLE_VQ_ADDR_IN_SUSPEND flag
> advertises this support as a backend features.

There's an ongoing effort in virtio spec to introduce the suspend state.

So I wonder if it's better to just allow such behaviour?

Thanks


>
> Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
> Suggested-by: Eugenio Pérez <eperezma@...hat.com>
> ---
>  include/uapi/linux/vhost_types.h | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
> index d7656908f730..aacd067afc89 100644
> --- a/include/uapi/linux/vhost_types.h
> +++ b/include/uapi/linux/vhost_types.h
> @@ -192,5 +192,9 @@ struct vhost_vdpa_iova_range {
>  #define VHOST_BACKEND_F_DESC_ASID    0x7
>  /* IOTLB don't flush memory mapping across device reset */
>  #define VHOST_BACKEND_F_IOTLB_PERSIST  0x8
> +/* Device supports changing virtqueue addresses when device is suspended
> + * and is in state DRIVER_OK.
> + */
> +#define VHOST_BACKEND_F_CHANGEABLE_VQ_ADDR_IN_SUSPEND  0x9
>
>  #endif
> --
> 2.43.0
>