linux-kernel - Re: [PATCH v7 kernel 4/5] virtio-balloon: define flags and head for host request vq

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Message-ID: <20170308060158-mutt-send-email-mst@kernel.org>
Date:   Wed, 8 Mar 2017 06:02:26 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Wei Wang <wei.w.wang@...el.com>
Cc:     virtio-dev@...ts.oasis-open.org, kvm@...r.kernel.org,
        qemu-devel@...gnu.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org,
        Liang Li <liang.z.li@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Cornelia Huck <cornelia.huck@...ibm.com>,
        Amit Shah <amit.shah@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Liang Li <liliang324@...il.com>
Subject: Re: [PATCH v7 kernel 4/5] virtio-balloon: define flags and head for
 host request vq

On Fri, Mar 03, 2017 at 01:40:29PM +0800, Wei Wang wrote:
> From: Liang Li <liang.z.li@...el.com>
> 
> Define the flags and head struct for a new host request virtual
> queue. Guest can get requests from host and then responds to
> them on this new virtual queue.
> Host can make use of this virtqueue to request the guest to do
> some operations, e.g. drop page cache, synchronize file system,
> etc. The hypervisor can get some of guest's runtime information
> through this virtual queue too, e.g. the guest's unused page
> information, which can be used for live migration optimization.
> 
> Signed-off-by: Liang Li <liang.z.li@...el.com>
> Signed-off-by: Wei Wang <wei.w.wang@...el.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Cornelia Huck <cornelia.huck@...ibm.com>
> Cc: Amit Shah <amit.shah@...hat.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Liang Li <liliang324@...il.com>
> Cc: Wei Wang <wei.w.wang@...el.com>

I prefer this squashed into next patch makes review easier.


> ---
>  include/uapi/linux/virtio_balloon.h | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> index ed627b2..630b0ef 100644
> --- a/include/uapi/linux/virtio_balloon.h
> +++ b/include/uapi/linux/virtio_balloon.h
> @@ -35,6 +35,7 @@
>  #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */
>  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
>  #define VIRTIO_BALLOON_F_CHUNK_TRANSFER	3 /* Transfer pages in chunks */
> +#define VIRTIO_BALLOON_F_HOST_REQ_VQ	4 /* Host request virtqueue */
>  
>  /* Size of a PFN in the balloon interface. */
>  #define VIRTIO_BALLOON_PFN_SHIFT 12
> @@ -94,4 +95,25 @@ struct virtio_balloon_resp_hdr {
>  	__le32 data_len; /* Payload len in bytes */
>  };
>  
> +enum virtio_balloon_req_id {
> +	/* Get unused page information */
> +	BALLOON_GET_UNUSED_PAGES,
> +};
> +
> +enum virtio_balloon_flag {
> +	/* Have more data for a request */
> +	BALLOON_FLAG_CONT,
> +	/* No more data for a request */
> +	BALLOON_FLAG_DONE,
> +};
> +
> +struct virtio_balloon_req_hdr {
> +	/* Used to distinguish different requests */
> +	__le16 cmd;
> +	/* Reserved */
> +	__le16 reserved[3];
> +	/* Request parameter */
> +	__le64 param;
> +};
> +
>  #endif /* _LINUX_VIRTIO_BALLOON_H */
> -- 
> 2.7.4