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Fri, 8 Mar 2024 13:39:05 +0000 Received: from PH0PR10MB4664.namprd10.prod.outlook.com ([fe80::75a:a398:452a:90a9]) by PH0PR10MB4664.namprd10.prod.outlook.com ([fe80::75a:a398:452a:90a9%6]) with mapi id 15.20.7362.024; Fri, 8 Mar 2024 13:39:04 +0000 Message-ID: <701ec0a8-0af0-4cad-af18-c5b66b955a6d@oracle.com> Date: Fri, 8 Mar 2024 08:39:00 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 0/8] virtio, vhost: Add VIRTIO_F_NOTIFICATION_DATA support Content-Language: en-US To: Lei Yang Cc: "Michael S. Tsirkin" , Jason Wang , qemu-devel@nongnu.org, si-wei.liu@oracle.com, boris.ostrovsky@oracle.com, raphael@enfabrica.net, kwolf@redhat.com, hreitz@redhat.com, pasic@linux.ibm.com, borntraeger@linux.ibm.com, farman@linux.ibm.com, thuth@redhat.com, richard.henderson@linaro.org, david@redhat.com, iii@linux.ibm.com, cohuck@redhat.com, Eugenio Perez Martin , pbonzini@redhat.com, fam@euphon.net, stefanha@redhat.com, qemu-block@nongnu.org, qemu-s390x@nongnu.org, virtio-fs@lists.linux.dev References: <20240304194612.611660-1-jonah.palmer@oracle.com> <20240306023143-mutt-send-email-mst@kernel.org> From: Jonah Palmer In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: BL1PR13CA0248.namprd13.prod.outlook.com (2603:10b6:208:2ba::13) To PH0PR10MB4664.namprd10.prod.outlook.com (2603:10b6:510:41::11) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR10MB4664:EE_|MW6PR10MB7639:EE_ 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Received-SPF: pass client-ip=205.220.177.32; envelope-from=jonah.palmer@oracle.com; helo=mx0b-00069f02.pphosted.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 3/8/24 8:28 AM, Lei Yang wrote: > Hi Jonah > > QE tested this series v1 with a tap device with vhost=off with > regression tests, everything works fine. And QE also add > "notification_data=true" to the qemu command line then got "1" when > performing the command [1] inside the guest. > [1] cut -c39 /sys/devices/pci0000:00/0000:00:01.3/0000:05:00.0/virtio1/features > > Tested-by: Lei Yang > Thank you for double-checking this series for me Lei! I appreciate it :) Jonah > On Thu, Mar 7, 2024 at 7:18 PM Eugenio Perez Martin wrote: >> >> On Wed, Mar 6, 2024 at 8:34 AM Michael S. Tsirkin wrote: >>> >>> On Wed, Mar 06, 2024 at 08:07:31AM +0100, Eugenio Perez Martin wrote: >>>> On Wed, Mar 6, 2024 at 6:34 AM Jason Wang wrote: >>>>> >>>>> On Tue, Mar 5, 2024 at 3:46 AM Jonah Palmer wrote: >>>>>> >>>>>> The goal of these patches are to add support to a variety of virtio and >>>>>> vhost devices for the VIRTIO_F_NOTIFICATION_DATA transport feature. This >>>>>> feature indicates that a driver will pass extra data (instead of just a >>>>>> virtqueue's index) when notifying the corresponding device. >>>>>> >>>>>> The data passed in by the driver when this feature is enabled varies in >>>>>> format depending on if the device is using a split or packed virtqueue >>>>>> layout: >>>>>> >>>>>> Split VQ >>>>>> - Upper 16 bits: shadow_avail_idx >>>>>> - Lower 16 bits: virtqueue index >>>>>> >>>>>> Packed VQ >>>>>> - Upper 16 bits: 1-bit wrap counter & 15-bit shadow_avail_idx >>>>>> - Lower 16 bits: virtqueue index >>>>>> >>>>>> Also, due to the limitations of ioeventfd not being able to carry the >>>>>> extra provided by the driver, ioeventfd is left disabled for any devices >>>>>> using this feature. >>>>> >>>>> Is there any method to overcome this? This might help for vhost. >>>>> >>>> >>>> As a half-baked idea, read(2)ing an eventfd descriptor returns an >>>> 8-byte integer already. The returned value of read depends on eventfd >>>> flags, but both have to do with the number of writes of the other end. >>>> >>>> My proposal is to replace this value with the last value written by >>>> the guest, so we can extract the virtio notification data from there. >>>> The behavior of read is similar to not-EFD_SEMAPHORE, reading a value >>>> and then blocking if read again without writes. The behavior of KVM >>>> writes is different, as it is not a counter anymore. >>>> >>>> Thanks! >>> >>> >>> I doubt you will be able to support this in ioeventfd... >> >> I agree. >> >>> But vhost does not really need the value at all. >>> So why mask out ioeventfd with vhost? >> >> The interface should not be able to start with vhost-kernel because >> the feature is not offered by the vhost-kernel device. So ioeventfd is >> always enabled with vhost-kernel. >> >> Or do you mean we should allow it and let vhost-kernel fetch data from >> the avail ring as usual? I'm ok with that but then the guest can place >> any value to it, so the driver cannot be properly "validated by >> software" that way. >> >>> vhost-vdpa is probably the only one that might need it... >> >> Right, but vhost-vdpa already supports doorbell memory regions so I >> guess it has little use, isn't it? >> >> Thanks! >> >>> >>> >>> >>>>> Thanks >>>>> >>>>>> >>>>>> A significant aspect of this effort has been to maintain compatibility >>>>>> across different backends. As such, the feature is offered by backend >>>>>> devices only when supported, with fallback mechanisms where backend >>>>>> support is absent. >>>>>> >>>>>> Jonah Palmer (8): >>>>>> virtio/virtio-pci: Handle extra notification data >>>>>> virtio-pci: Lock ioeventfd state with VIRTIO_F_NOTIFICATION_DATA >>>>>> virtio-mmio: Handle extra notification data >>>>>> virtio-mmio: Lock ioeventfd state with VIRTIO_F_NOTIFICATION_DATA >>>>>> virtio-ccw: Handle extra notification data >>>>>> virtio-ccw: Lock ioeventfd state with VIRTIO_F_NOTIFICATION_DATA >>>>>> vhost/vhost-user: Add VIRTIO_F_NOTIFICATION_DATA to vhost feature bits >>>>>> virtio: Add VIRTIO_F_NOTIFICATION_DATA property definition >>>>>> >>>>>> hw/block/vhost-user-blk.c | 1 + >>>>>> hw/net/vhost_net.c | 2 ++ >>>>>> hw/s390x/s390-virtio-ccw.c | 16 ++++++++++++---- >>>>>> hw/s390x/virtio-ccw.c | 6 ++++-- >>>>>> hw/scsi/vhost-scsi.c | 1 + >>>>>> hw/scsi/vhost-user-scsi.c | 1 + >>>>>> hw/virtio/vhost-user-fs.c | 2 +- >>>>>> hw/virtio/vhost-user-vsock.c | 1 + >>>>>> hw/virtio/virtio-mmio.c | 15 +++++++++++---- >>>>>> hw/virtio/virtio-pci.c | 16 +++++++++++----- >>>>>> hw/virtio/virtio.c | 18 ++++++++++++++++++ >>>>>> include/hw/virtio/virtio.h | 5 ++++- >>>>>> net/vhost-vdpa.c | 1 + >>>>>> 13 files changed, 68 insertions(+), 17 deletions(-) >>>>>> >>>>>> -- >>>>>> 2.39.3 >>>>>> >>>>> >>> >> >> >