Re: [PATCH v3 01/17] virtio_pci: struct virtio_pci_common_cfg add queue_notify_data

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
To: Jason Wang <jasowang@redhat.com>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	netdev <netdev@vger.kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	virtualization <virtualization@lists.linux-foundation.org>,
	Jakub Kicinski <kuba@kernel.org>,
	bpf@vger.kernel.org, "David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH v3 01/17] virtio_pci: struct virtio_pci_common_cfg add queue_notify_data
Date: Tue, 08 Feb 2022 10:17:29 +0800	[thread overview]
Message-ID: <1644286649.5989025-1-xuanzhuo@linux.alibaba.com> (raw)
In-Reply-To: <CACGkMEuJ_v5g2ypLZ3eNhAcUM9Q3PpWuiaeWVfEC6KACGzWAZw@mail.gmail.com>

On Mon, 7 Feb 2022 16:06:15 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Mon, Feb 7, 2022 at 2:07 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > On Mon, 7 Feb 2022 11:41:06 +0800, Jason Wang <jasowang@redhat.com> wrote:
> > >
> > > 在 2022/1/26 下午3:35, Xuan Zhuo 写道:
> > > > Add queue_notify_data in struct virtio_pci_common_cfg, which comes from
> > > > here https://github.com/oasis-tcs/virtio-spec/issues/89
> > > >
> > > > Since I want to add queue_reset after it, I submitted this patch first.
> > > >
> > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > > ---
> > > >   include/uapi/linux/virtio_pci.h | 1 +
> > > >   1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
> > > > index 3a86f36d7e3d..492c89f56c6a 100644
> > > > --- a/include/uapi/linux/virtio_pci.h
> > > > +++ b/include/uapi/linux/virtio_pci.h
> > > > @@ -164,6 +164,7 @@ struct virtio_pci_common_cfg {
> > > >     __le32 queue_avail_hi;          /* read-write */
> > > >     __le32 queue_used_lo;           /* read-write */
> > > >     __le32 queue_used_hi;           /* read-write */
> > > > +   __le16 queue_notify_data;       /* read-write */
> > > >   };
> > >
> > >
> > > So I had the same concern as previous version.
> > >
> > > This breaks uABI where program may try to use sizeof(struct
> > > virtio_pci_common_cfg).
> > >
> > > We probably need a container structure here.
> >
> > I see, I plan to add a struct like this, do you think it's appropriate?
> >
> > struct virtio_pci_common_cfg_v1 {
> >         struct virtio_pci_common_cfg cfg;
> >         __le16 queue_notify_data;       /* read-write */
> > }
>
> Something like this but we probably need a better name.

how about this?

	/* Ext Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
	struct virtio_pci_common_cfg_ext {
		struct virtio_pci_common_cfg cfg;

		__le16 queue_notify_data;	/* read-write */

		__le16 reserved0;
		__le16 reserved1;
		__le16 reserved2;
		__le16 reserved3;
		__le16 reserved4;
		__le16 reserved5;
		__le16 reserved6;
		__le16 reserved7;
		__le16 reserved8;
		__le16 reserved9;
		__le16 reserved10;
		__le16 reserved11;
		__le16 reserved12;
		__le16 reserved13;
		__le16 reserved14;
	};

Thanks

>
> Thanks
>
> >
> > Thanks.
> >
> > >
> > > THanks
> > >
> > >
> > > >
> > > >   /* Fields in VIRTIO_PCI_CAP_PCI_CFG: */
> > >
> >
>
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