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[209.132.180.67]) by mx.google.com with ESMTP id w2si4977587pfg.78.2018.11.30.08.27.48; Fri, 30 Nov 2018 08:28:14 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727583AbeLADf7 (ORCPT + 99 others); Fri, 30 Nov 2018 22:35:59 -0500 Received: from mga02.intel.com ([134.134.136.20]:13081 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727500AbeLADf6 (ORCPT ); Fri, 30 Nov 2018 22:35:58 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Nov 2018 08:26:07 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,299,1539673200"; d="scan'208";a="105620753" Received: from btwcube1.sh.intel.com (HELO debian) ([10.67.104.173]) by orsmga003.jf.intel.com with ESMTP; 30 Nov 2018 08:26:05 -0800 Date: Sat, 1 Dec 2018 00:24:16 +0800 From: Tiwei Bie To: "Michael S. Tsirkin" Cc: Maxime Coquelin , Jason Wang , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, virtio-dev@lists.oasis-open.org, wexu@redhat.com, jfreimann@redhat.com Subject: Re: [PATCH net-next v3 01/13] virtio: add packed ring types and macros Message-ID: <20181130162416.GA19234@debian> References: <20181121100330.24846-1-tiwei.bie@intel.com> <20181121100330.24846-2-tiwei.bie@intel.com> <1928ac96-3684-45c4-1e8c-09dff03bf308@redhat.com> <20181130095339.GA11984@debian> <20181130074720-mutt-send-email-mst@kernel.org> <13593b5c-c1dc-3ab3-a843-d62908e0c7e0@redhat.com> <20181130084722-mutt-send-email-mst@kernel.org> <20181130153737.GA15105@debian> <20181130104957-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181130104957-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 30, 2018 at 10:53:07AM -0500, Michael S. Tsirkin wrote: > On Fri, Nov 30, 2018 at 11:37:37PM +0800, Tiwei Bie wrote: > > On Fri, Nov 30, 2018 at 08:52:42AM -0500, Michael S. Tsirkin wrote: > > > On Fri, Nov 30, 2018 at 02:01:06PM +0100, Maxime Coquelin wrote: > > > > On 11/30/18 1:47 PM, Michael S. Tsirkin wrote: > > > > > On Fri, Nov 30, 2018 at 05:53:40PM +0800, Tiwei Bie wrote: > > > > > > On Fri, Nov 30, 2018 at 04:10:55PM +0800, Jason Wang wrote: > > > > > > > > > > > > > > On 2018/11/21 下午6:03, Tiwei Bie wrote: > > > > > > > > Add types and macros for packed ring. > > > > > > > > > > > > > > > > Signed-off-by: Tiwei Bie > > > > > > > > --- > > > > > > > > include/uapi/linux/virtio_config.h | 3 +++ > > > > > > > > include/uapi/linux/virtio_ring.h | 52 ++++++++++++++++++++++++++++++++++++++ > > > > > > > > 2 files changed, 55 insertions(+) > > > > > > > > > > > > > > > > diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h > > > > > > > > index 449132c76b1c..1196e1c1d4f6 100644 > > > > > > > > --- a/include/uapi/linux/virtio_config.h > > > > > > > > +++ b/include/uapi/linux/virtio_config.h > > > > > > > > @@ -75,6 +75,9 @@ > > > > > > > > */ > > > > > > > > #define VIRTIO_F_IOMMU_PLATFORM 33 > > > > > > > > +/* This feature indicates support for the packed virtqueue layout. */ > > > > > > > > +#define VIRTIO_F_RING_PACKED 34 > > > > > > > > + > > > > > > > > /* > > > > > > > > * Does the device support Single Root I/O Virtualization? > > > > > > > > */ > > > > > > > > diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h > > > > > > > > index 6d5d5faa989b..2414f8af26b3 100644 > > > > > > > > --- a/include/uapi/linux/virtio_ring.h > > > > > > > > +++ b/include/uapi/linux/virtio_ring.h > > > > > > > > @@ -44,6 +44,13 @@ > > > > > > > > /* This means the buffer contains a list of buffer descriptors. */ > > > > > > > > #define VRING_DESC_F_INDIRECT 4 > > > > > > > > +/* > > > > > > > > + * Mark a descriptor as available or used in packed ring. > > > > > > > > + * Notice: they are defined as shifts instead of shifted values. > > > > > > > > > > > > > > > > > > > > > This looks inconsistent to previous flags, any reason for using shifts? > > > > > > > > > > > > Yeah, it was suggested to use shifts, as _F_ should be a bit > > > > > > number, not a shifted value: > > > > > > > > > > > > https://patchwork.ozlabs.org/patch/942296/#1989390 > > > > > > > > > > But let's add a _SPLIT_ variant that uses shifts consistently. > > > > > > > > Maybe we could avoid adding SPLIT and PACKED, but define as follow: > > > > > > > > #define VRING_DESC_F_INDIRECT_SHIFT 2 > > > > #define VRING_DESC_F_INDIRECT (1ull << VRING_DESC_F_INDIRECT_SHIFT) > > > > > > > > #define VRING_DESC_F_AVAIL_SHIFT 7 > > > > #define VRING_DESC_F_AVAIL (1ull << VRING_DESC_F_AVAIL_SHIFT) > > > > > > > > I think it would be better for consistency. > > > > > > I don't think that will help. the problem is that > > > most of the existing virtio code consistently uses _F_ as shifts. > > > So we just need to do something about these 5 being inconsistent: > > > > > > include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_NEXT 1 > > > include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_WRITE 2 > > > include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_INDIRECT 4 > > > include/uapi/linux/virtio_ring.h:#define VRING_USED_F_NO_NOTIFY 1 > > > include/uapi/linux/virtio_ring.h:#define VRING_AVAIL_F_NO_INTERRUPT 1 > > > > > > I do not want all of virtio to become verbose with _SHIFT, ergo > > > we need to change the above 5 to have names which are with _F_ and > > > have the bit number. > > > > How about something like this: > > > > #define VRING_COMM_DESC_F_NEXT 0 > > #define VRING_COMM_DESC_F_WRITE 1 > > #define VRING_COMM_DESC_F_INDIRECT 2 > > > > #define VRING_SPLIT_USED_F_NO_NOTIFY 0 > > #define VRING_SPLIT_AVAIL_F_NO_INTERRUPT 0 > > > > or > > > > #define VRING_SPLIT_DESC_F_NEXT 0 > > #define VRING_SPLIT_DESC_F_WRITE 1 > > #define VRING_SPLIT_DESC_F_INDIRECT 2 > > > > #define VRING_SPLIT_USED_F_NO_NOTIFY 0 > > #define VRING_SPLIT_AVAIL_F_NO_INTERRUPT 0 > > > > #define VRING_PACKED_DESC_F_NEXT 0 > > #define VRING_PACKED_DESC_F_WRITE 1 > > #define VRING_PACKED_DESC_F_INDIRECT 2 > > As we aren't sharing code I think I prefer the second form. > Maybe add VRING_NO_LEGACY so people can audit their code > for assumptions? Maybe it's better to name it as VIRTIO_RING_NO_LEGACY which is more consistent with the names in other files. > > We also want to guard layout definitions at the end of that file > I think. Do you mean guard the definitions of `struct vring` and `struct vring_packed` with _NO_LEGACY? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > + */ > > > > > > > > +#define VRING_PACKED_DESC_F_AVAIL 7 > > > > > > > > +#define VRING_PACKED_DESC_F_USED 15 > > > > > > > > + > > > > > > > > /* The Host uses this in used->flags to advise the Guest: don't kick me when > > > > > > > > * you add a buffer. It's unreliable, so it's simply an optimization. Guest > > > > > > > > * will still kick if it's out of buffers. */ > > > > > > > > @@ -53,6 +60,23 @@ > > > > > > > > * optimization. */ > > > > > > > > #define VRING_AVAIL_F_NO_INTERRUPT 1 > > > > > > > > +/* Enable events in packed ring. */ > > > > > > > > +#define VRING_PACKED_EVENT_FLAG_ENABLE 0x0 > > > > > > > > +/* Disable events in packed ring. */ > > > > > > > > +#define VRING_PACKED_EVENT_FLAG_DISABLE 0x1 > > > > > > > > +/* > > > > > > > > + * Enable events for a specific descriptor in packed ring. > > > > > > > > + * (as specified by Descriptor Ring Change Event Offset/Wrap Counter). > > > > > > > > + * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated. > > > > > > > > + */ > > > > > > > > +#define VRING_PACKED_EVENT_FLAG_DESC 0x2 > > > > > > > > > > > > > > > > > > > > > Any reason for using _FLAG_ instead of _F_? > > > > > > > > > > > > Yeah, it was suggested to not use _F_, as these are values, > > > > > > should not have _F_: > > > > > > > > > > > > https://patchwork.ozlabs.org/patch/942296/#1989390 > > > > > > > > > > > > Regards, > > > > > > Tiwei > > > > > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > + > > > > > > > > +/* > > > > > > > > + * Wrap counter bit shift in event suppression structure > > > > > > > > + * of packed ring. > > > > > > > > + */ > > > > > > > > +#define VRING_PACKED_EVENT_F_WRAP_CTR 15 > > > > > > > > + > > > > > > > > /* We support indirect buffer descriptors */ > > > > > > > > #define VIRTIO_RING_F_INDIRECT_DESC 28 > > > > > > > > @@ -171,4 +195,32 @@ static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old) > > > > > > > > return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old); > > > > > > > > } > > > > > > > > +struct vring_packed_desc_event { > > > > > > > > + /* Descriptor Ring Change Event Offset/Wrap Counter. */ > > > > > > > > + __le16 off_wrap; > > > > > > > > + /* Descriptor Ring Change Event Flags. */ > > > > > > > > + __le16 flags; > > > > > > > > +}; > > > > > > > > + > > > > > > > > +struct vring_packed_desc { > > > > > > > > + /* Buffer Address. */ > > > > > > > > + __le64 addr; > > > > > > > > + /* Buffer Length. */ > > > > > > > > + __le32 len; > > > > > > > > + /* Buffer ID. */ > > > > > > > > + __le16 id; > > > > > > > > + /* The flags depending on descriptor type. */ > > > > > > > > + __le16 flags; > > > > > > > > +}; > > > > > > > > + > > > > > > > > +struct vring_packed { > > > > > > > > + unsigned int num; > > > > > > > > + > > > > > > > > + struct vring_packed_desc *desc; > > > > > > > > + > > > > > > > > + struct vring_packed_desc_event *driver; > > > > > > > > + > > > > > > > > + struct vring_packed_desc_event *device; > > > > > > > > +}; > > > > > > > > + > > > > > > > > #endif /* _UAPI_LINUX_VIRTIO_RING_H */