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Wed, 15 Sep 2021 00:38:35 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxjJG5HmRxot3O+sRXKAYzInQI3onfnVJshUEWm0IVFrmhJ/2Pm3nYzdj3Jd9vbXIIUP6W/VQ== X-Received: by 2002:a17:906:7208:: with SMTP id m8mr23518933ejk.82.1631691514844; Wed, 15 Sep 2021 00:38:34 -0700 (PDT) Received: from redhat.com ([2.55.157.56]) by smtp.gmail.com with ESMTPSA id n3sm6657200eds.79.2021.09.15.00.38.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Sep 2021 00:38:34 -0700 (PDT) Date: Wed, 15 Sep 2021 03:38:31 -0400 From: "Michael S. Tsirkin" To: Jason Wang Subject: Re: [PATCH v2 4/5] vdpa: add new vdpa attribute VDPA_ATTR_DEV_F_VERSION_1 Message-ID: <20210915033756-mutt-send-email-mst@kernel.org> References: <834528d24c839080215b2e077f100e9ed5073edc.1631621507.git.wuzongyong@linux.alibaba.com> <20210914085711-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: wei.yang1@linux.alibaba.com, Wu Zongyong , linux-kernel , virtualization X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Wed, Sep 15, 2021 at 11:18:06AM +0800, Jason Wang wrote: > On Tue, Sep 14, 2021 at 8:58 PM Michael S. Tsirkin wrote: > > > > On Tue, Sep 14, 2021 at 08:24:51PM +0800, Wu Zongyong wrote: > > > This new attribute advertises whether the vdpa device is legacy or not. > > > Users can pick right virtqueue size if the vdpa device is legacy which > > > doesn't support to change virtqueue size. > > > > > > Signed-off-by: Wu Zongyong > > > > So if we are bothering with legacy, > > I think we'd better not. I guess the following may work: > > 1) disable the driver on BE host > 2) present VERSION_1 with ACCESS_PLATFORM in get_features() > 3) extend the management to advertise max_queue_size and > min_queue_size, for ENI they are the same so management layer knows it > needs to set the queue_size correctly during launching qemu > > Thoughts? > > Thanks There are other subtle differences such as header size without mergeable buffers for net. > > I think there are > > several things to do when building the interface > > - support transitional devices, that is allow userspace > > to tell device it's in legacy mode > > - support reporting/setting supporting endian-ness > > > > > --- > > > drivers/vdpa/vdpa.c | 6 ++++++ > > > drivers/virtio/virtio_vdpa.c | 7 ++++++- > > > include/uapi/linux/vdpa.h | 1 + > > > 3 files changed, 13 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c > > > index 1dc121a07a93..533d7f589eee 100644 > > > --- a/drivers/vdpa/vdpa.c > > > +++ b/drivers/vdpa/vdpa.c > > > @@ -12,6 +12,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > #include > > > #include > > > > > > @@ -494,6 +495,7 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq > > > u16 max_vq_size; > > > u32 device_id; > > > u32 vendor_id; > > > + u64 features; > > > void *hdr; > > > int err; > > > > > > @@ -508,6 +510,7 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq > > > device_id = vdev->config->get_device_id(vdev); > > > vendor_id = vdev->config->get_vendor_id(vdev); > > > max_vq_size = vdev->config->get_vq_num_max(vdev); > > > + features = vdev->config->get_features(vdev); > > > > > > err = -EMSGSIZE; > > > if (nla_put_string(msg, VDPA_ATTR_DEV_NAME, dev_name(&vdev->dev))) > > > @@ -520,6 +523,9 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq > > > goto msg_err; > > > if (nla_put_u16(msg, VDPA_ATTR_DEV_MAX_VQ_SIZE, max_vq_size)) > > > goto msg_err; > > > + if (features & BIT_ULL(VIRTIO_F_VERSION_1) && > > > + nla_put_flag(msg, VDPA_ATTR_DEV_VERSION_1)) > > > + goto msg_err; > > > > > > genlmsg_end(msg, hdr); > > > return 0; > > > diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c > > > index 72eaef2caeb1..1cba957c4cdc 100644 > > > --- a/drivers/virtio/virtio_vdpa.c > > > +++ b/drivers/virtio/virtio_vdpa.c > > > @@ -7,6 +7,7 @@ > > > * > > > */ > > > > > > +#include "linux/virtio_config.h" > > > #include > > > #include > > > #include > > > @@ -145,6 +146,7 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index, > > > /* Assume split virtqueue, switch to packed if necessary */ > > > struct vdpa_vq_state state = {0}; > > > unsigned long flags; > > > + bool may_reduce_num = false; > > > u32 align, num; > > > int err; > > > > > > @@ -169,10 +171,13 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index, > > > goto error_new_virtqueue; > > > } > > > > > > + if (ops->get_features(vdpa) & BIT_ULL(VIRTIO_F_VERSION_1)) > > > + may_reduce_num = true; > > > + > > > /* Create the vring */ > > > align = ops->get_vq_align(vdpa); > > > vq = vring_create_virtqueue(index, num, align, vdev, > > > - true, true, ctx, > > > + true, may_reduce_num, ctx, > > > virtio_vdpa_notify, callback, name); > > > if (!vq) { > > > err = -ENOMEM; > > > diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h > > > index 66a41e4ec163..ce0b74276a5b 100644 > > > --- a/include/uapi/linux/vdpa.h > > > +++ b/include/uapi/linux/vdpa.h > > > @@ -32,6 +32,7 @@ enum vdpa_attr { > > > VDPA_ATTR_DEV_VENDOR_ID, /* u32 */ > > > VDPA_ATTR_DEV_MAX_VQS, /* u32 */ > > > VDPA_ATTR_DEV_MAX_VQ_SIZE, /* u16 */ > > > + VDPA_ATTR_DEV_VERSION_1, /* flag */ > > > > > > /* new attributes must be added above here */ > > > VDPA_ATTR_MAX, > > > -- > > > 2.31.1 > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization