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Tue, 5 Nov 2019 05:24:16 +0000 (UTC) Received: from [10.72.12.252] (ovpn-12-252.pek2.redhat.com [10.72.12.252]) by smtp.corp.redhat.com (Postfix) with ESMTP id 85B7F5D9CD; Tue, 5 Nov 2019 05:22:58 +0000 (UTC) Subject: Re: [PATCH V7 4/6] mdev: introduce virtio device and its device ops To: Alex Williamson Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, kwankhede@nvidia.com, mst@redhat.com, tiwei.bie@intel.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, cohuck@redhat.com, maxime.coquelin@redhat.com, cunming.liang@intel.com, zhihong.wang@intel.com, rob.miller@broadcom.com, xiao.w.wang@intel.com, haotian.wang@sifive.com, zhenyuw@linux.intel.com, zhi.a.wang@intel.com, jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, airlied@linux.ie, daniel@ffwll.ch, farman@linux.ibm.com, pasic@linux.ibm.com, sebott@linux.ibm.com, oberpar@linux.ibm.com, heiko.carstens@de.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, akrowiak@linux.ibm.com, freude@linux.ibm.com, lingshan.zhu@intel.com, idos@mellanox.com, eperezma@redhat.com, lulu@redhat.com, parav@mellanox.com, christophe.de.dinechin@gmail.com, kevin.tian@intel.com, stefanha@redhat.com References: <20191104123952.17276-1-jasowang@redhat.com> <20191104123952.17276-5-jasowang@redhat.com> <20191104145024.5e437765@x1.home> <1faf4f36-3f79-2e15-3f61-c406d68240ab@redhat.com> <20191104213920.59d356a3@x1.home> From: Jason Wang Message-ID: <970f2107-2677-6578-ce99-65083716d04d@redhat.com> Date: Tue, 5 Nov 2019 13:22:50 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191104213920.59d356a3@x1.home> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: 9DP0etJzPRutiF5l4L2myw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2019/11/5 =E4=B8=8B=E5=8D=8812:39, Alex Williamson wrote: > On Tue, 5 Nov 2019 11:52:41 +0800 > Jason Wang wrote: > >> On 2019/11/5 =E4=B8=8A=E5=8D=885:50, Alex Williamson wrote: >>> On Mon, 4 Nov 2019 20:39:50 +0800 >>> Jason Wang wrote: >>> =20 >>>> This patch implements basic support for mdev driver that supports >>>> virtio transport for kernel virtio driver. >>>> >>>> Signed-off-by: Jason Wang >>>> --- >>>> drivers/vfio/mdev/mdev_core.c | 20 ++++ >>>> drivers/vfio/mdev/mdev_private.h | 2 + >>>> include/linux/mdev.h | 6 ++ >>>> include/linux/mdev_virtio_ops.h | 166 ++++++++++++++++++++++++++++= +++ >>>> 4 files changed, 194 insertions(+) >>>> create mode 100644 include/linux/mdev_virtio_ops.h >>>> >>>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_co= re.c >>>> index 8d579d7ed82f..95ee4126ff9c 100644 >>>> --- a/drivers/vfio/mdev/mdev_core.c >>>> +++ b/drivers/vfio/mdev/mdev_core.c >>>> @@ -76,6 +76,26 @@ const struct mdev_vfio_device_ops *mdev_get_vfio_op= s(struct mdev_device *mdev) >>>> } >>>> EXPORT_SYMBOL(mdev_get_vfio_ops); >>>> =20 >>>> +/* Specify the virtio device ops for the mdev device, this >>>> + * must be called during create() callback for virtio mdev device. >>>> + */ >>> Comment style. >> >> Will fix. >> >> >>> =20 >>>> +void mdev_set_virtio_ops(struct mdev_device *mdev, >>>> +=09=09=09 const struct mdev_virtio_device_ops *virtio_ops) >>>> +{ >>>> +=09mdev_set_class(mdev, MDEV_CLASS_ID_VIRTIO); >>>> +=09mdev->virtio_ops =3D virtio_ops; >>>> +} >>>> +EXPORT_SYMBOL(mdev_set_virtio_ops); >>>> + >>>> +/* Get the virtio device ops for the mdev device. */ >>>> +const struct mdev_virtio_device_ops * >>>> +mdev_get_virtio_ops(struct mdev_device *mdev) >>>> +{ >>>> +=09WARN_ON(mdev->class_id !=3D MDEV_CLASS_ID_VIRTIO); >>>> +=09return mdev->virtio_ops; >>>> +} >>>> +EXPORT_SYMBOL(mdev_get_virtio_ops); >>>> + >>>> struct device *mdev_dev(struct mdev_device *mdev) >>>> { >>>> =09return &mdev->dev; >>>> diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev= _private.h >>>> index 411227373625..2c74dd032409 100644 >>>> --- a/drivers/vfio/mdev/mdev_private.h >>>> +++ b/drivers/vfio/mdev/mdev_private.h >>>> @@ -11,6 +11,7 @@ >>>> #define MDEV_PRIVATE_H >>>> =20 >>>> #include >>>> +#include >>>> =20 >>>> int mdev_bus_register(void); >>>> void mdev_bus_unregister(void); >>>> @@ -38,6 +39,7 @@ struct mdev_device { >>>> =09u16 class_id; >>>> =09union { >>>> =09=09const struct mdev_vfio_device_ops *vfio_ops; >>>> +=09=09const struct mdev_virtio_device_ops *virtio_ops; >>>> =09}; >>>> }; >>>> =20 >>>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h >>>> index 9e37506d1987..f3d75a60c2b5 100644 >>>> --- a/include/linux/mdev.h >>>> +++ b/include/linux/mdev.h >>>> @@ -17,6 +17,7 @@ >>>> =20 >>>> struct mdev_device; >>>> struct mdev_vfio_device_ops; >>>> +struct mdev_virtio_device_ops; >>>> =20 >>>> /* >>>> * Called by the parent device driver to set the device which repre= sents >>>> @@ -112,6 +113,10 @@ void mdev_set_class(struct mdev_device *mdev, u16= id); >>>> void mdev_set_vfio_ops(struct mdev_device *mdev, >>>> =09=09 const struct mdev_vfio_device_ops *vfio_ops); >>>> const struct mdev_vfio_device_ops *mdev_get_vfio_ops(struct mdev_de= vice *mdev); >>>> +void mdev_set_virtio_ops(struct mdev_device *mdev, >>>> +=09=09=09 const struct mdev_virtio_device_ops *virtio_ops); >>>> +const struct mdev_virtio_device_ops * >>>> +mdev_get_virtio_ops(struct mdev_device *mdev); >>>> =20 >>>> extern struct bus_type mdev_bus_type; >>>> =20 >>>> @@ -127,6 +132,7 @@ struct mdev_device *mdev_from_dev(struct device *d= ev); >>>> =20 >>>> enum { >>>> =09MDEV_CLASS_ID_VFIO =3D 1, >>>> +=09MDEV_CLASS_ID_VIRTIO =3D 2, >>>> =09/* New entries must be added here */ >>>> }; >>>> =20 >>>> diff --git a/include/linux/mdev_virtio_ops.h b/include/linux/mdev_virt= io_ops.h >>>> new file mode 100644 >>>> index 000000000000..0dcae7fa31e5 >>>> --- /dev/null >>>> +++ b/include/linux/mdev_virtio_ops.h >>>> @@ -0,0 +1,166 @@ >>>> +/* SPDX-License-Identifier: GPL-2.0-only */ >>>> +/* >>>> + * Virtio mediated device driver >>>> + * >>>> + * Copyright 2019, Red Hat Corp. >>>> + * Author: Jason Wang >>>> + */ >>>> +#ifndef MDEV_VIRTIO_OPS_H >>>> +#define MDEV_VIRTIO_OPS_H >>>> + >>>> +#include >>>> +#include >>>> +#include >>>> + >>>> +#define VIRTIO_MDEV_DEVICE_API_STRING=09=09"virtio-mdev" >>>> +#define VIRTIO_MDEV_F_VERSION_1 0x1 >>>> + >>>> +struct virtio_mdev_callback { >>>> +=09irqreturn_t (*callback)(void *data); >>>> +=09void *private; >>>> +}; >>>> + >>>> +/** >>>> + * struct mdev_virtio_device_ops - Structure to be registered for eac= h >>>> + * mdev device to register the device for virtio/vhost drivers. >>>> + * >>>> + * The device ops that is supported by VIRTIO_MDEV_F_VERSION_1, the >>>> + * callbacks are mandatory unless explicity mentioned. >>>> + * >>>> + * @get_mdev_features:=09=09Get a set of bits that demonstrate >>>> + *=09=09=09=09the capability of the mdev device. New >>>> + *=09=09=09=09feature bits must be added when >>>> + *=09=09=09=09introducing new device ops. This >>>> + *=09=09=09=09allows the device ops to be extended >>>> + *=09=09=09=09(one feature could have N new ops). >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09Returns the mdev features (API) support by >>>> + *=09=09=09=09the device. >>> I still don't see the point of VIRTIO_MDEV_F_VERSION_1. In what case >>> would it not be set? >> >> It's a must for current driver implementation. >> >> >>> What would it indicate to the caller if it were >>> not set? The existence of this interface seems to indicate version 1. >> >> The idea is when VIRTIO_MDE_F_VERSION_1 is advertised, driver will >> assume all the mandatory callbacks for this feature were implemented. >> Then there's no need to check the existence of each callback. > But this is redundant to MDEV_CLASS_ID_VIRTIO, which must imply the > struct mdev_virtio_device_ops or else we have no handshake between the > mdev device and the mdev bus driver. Essentially this creates a flag > that says there are no flags, which is useless. I can't see why > checking feature bits here is preferable to checking callbacks. Ok, so I think the point is that we can assume the existence for some=20 callbacks from the start. > >>> I'm also still unclear how device ops gets extended, can you give some >>> examples? Particularly, if feature A and feature B both add device ops >>> callbacks, is the vendor allowed to support B but not A, and does that >>> imply their device ops structure includes callbacks for A but they're >>> unused? >> >> For current API, the answer is yes. So if vendor only support feature B, >> it needs to set the device_ops that support feature A to NULL. > Which is exactly what we expect to happen with get_generation() but we > can't be bothered to add a feature flag for it? The interface is > already self inconsistent. For get_generation(), we can do simply fallback by return zero (like=20 what virito core did). But for other feature, we can not have such=20 fallback easily. > >>> Why doesn't the previous patch take any of this into account >>> for struct mdev_vfio_device_ops? I think this is an internal API, >>> therefore is it worthwhile to include feature and extension support? >> >> I'm not sure if VFIO has the request. In that case new features could be >> extended simply through transport/bus specific way (e.g PCIE capability >> list). But in the case of virtio-mdev, we need invent something on our >> own. If the simple mapping between features and device ops is proved to >> be not sufficient or sub-optimal, we can introduce a more sophisticated >> API. > I think the key is that device ops is not an ABI, if we add new > callbacks we can extend the structures of all the vendor drivers and > the mdev bus driver can either choose to test the callback at runtime > or probe time. I really don't see what we're accomplishing with this > callback. > >>>> + * @get_mdev_features:=09=09Set a set of features that will be >>> s/get/set/ >> >> Will fix. >> >> >>> =20 >>>> + *=09=09=09=09used by the driver. >>>> + *=09=09=09=09@features: features used by the driver >>>> + *=09=09=09=09Returns bollean: whether the features >>> s/bollean/boolean/ >>> >>> How does one provide a set of features to set given this prototype? >>> >>> bool (*set_mdev_feature)(struct mdev_device *mdev); >>> >>> This is starting to look like a grab bag of callbacks, what sort of >>> mdev features would the driver have the ability to set on a device? >> >> Yes, e.g device support A,B,C, but driver will only use B and C. > Can you give a _concrete_ example of such features where the device > needs to be informed of what features the driver will use rather than > simply not using them? Two examples: - dirty page logging by device - control vq support So device can choose to support one of the above features. > There appears to be no use case for this > currently, so I'd suggest dropping it. If such a feature becomes > necessary it can be added as needed since this is an internal > interface. Ok, I think I get your point. I worried about the vhost-mdev but anyway=20 those API is not exposed to user directly. I will drop those in next=20 version. > Also not sure my point above was well conveyed, the > prototype doesn't provide a feature arg in order to set features. The > comment also indicates we can set a set of features (ie. multiple), but > it's not well specified what a failure indicates or why we'd use a > boolean to indicate a failure versus an errno where we could interpret > the return code. Both these callbacks seem like placeholders, which > should be unnecessary as this is simply an internal API between > virtio-mdev vendor drivers and the bus driver. Thanks, I see. Thanks > > Alex > >>> Note that this is not listed as optional, but the sample driver doesn't >>> implement it :-\ >> >> My bad, will fix this. >> >> Thanks >> >> >>> Thanks, >>> >>> Alex >>> =20 >>>> + *=09=09=09=09is accepted by the device. >>>> + * @set_vq_address:=09=09Set the address of virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@idx: virtqueue index >>>> + *=09=09=09=09@desc_area: address of desc area >>>> + *=09=09=09=09@driver_area: address of driver area >>>> + *=09=09=09=09@device_area: address of device area >>>> + *=09=09=09=09Returns integer: success (0) or error (< 0) >>>> + * @set_vq_num:=09=09=09Set the size of virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@idx: virtqueue index >>>> + *=09=09=09=09@num: the size of virtqueue >>>> + * @kick_vq:=09=09=09Kick the virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@idx: virtqueue index >>>> + * @set_vq_cb:=09=09=09Set the interrupt callback function for >>>> + *=09=09=09=09a virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@idx: virtqueue index >>>> + *=09=09=09=09@cb: virtio-mdev interrupt callback structure >>>> + * @set_vq_ready:=09=09Set ready status for a virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@idx: virtqueue index >>>> + *=09=09=09=09@ready: ready (true) not ready(false) >>>> + * @get_vq_ready:=09=09Get ready status for a virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@idx: virtqueue index >>>> + *=09=09=09=09Returns boolean: ready (true) or not (false) >>>> + * @set_vq_state:=09=09Set the state for a virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@idx: virtqueue index >>>> + *=09=09=09=09@state: virtqueue state (last_avail_idx) >>>> + *=09=09=09=09Returns integer: success (0) or error (< 0) >>>> + * @get_vq_state:=09=09Get the state for a virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@idx: virtqueue index >>>> + *=09=09=09=09Returns virtqueue state (last_avail_idx) >>>> + * @get_vq_align:=09=09Get the virtqueue align requirement >>>> + *=09=09=09=09for the device >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09Returns virtqueue algin requirement >>>> + * @get_features:=09=09Get virtio features supported by the device >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09Returns the virtio features support by the >>>> + *=09=09=09=09device >>>> + * @set_features:=09=09Set virtio features supported by the driver >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@features: feature support by the driver >>>> + *=09=09=09=09Returns integer: success (0) or error (< 0) >>>> + * @set_config_cb:=09=09Set the config interrupt callback >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@cb: virtio-mdev interrupt callback structure >>>> + * @get_vq_num_max:=09=09Get the max size of virtqueue >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09Returns u16: max size of virtqueue >>>> + * @get_device_id:=09=09Get virtio device id >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09Returns u32: virtio device id >>>> + * @get_vendor_id:=09=09Get id for the vendor that provides this devi= ce >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09Returns u32: virtio vendor id >>>> + * @get_status:=09=09=09Get the device status >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09Returns u8: virtio device status >>>> + * @set_status:=09=09=09Set the device status >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@status: virtio device status >>>> + * @get_config:=09=09=09Read from device specific configuration space >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@offset: offset from the beginning of >>>> + *=09=09=09=09configuration space >>>> + *=09=09=09=09@buf: buffer used to read to >>>> + *=09=09=09=09@len: the length to read from >>>> + *=09=09=09=09configration space >>>> + * @set_config:=09=09=09Write to device specific configuration space >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09@offset: offset from the beginning of >>>> + *=09=09=09=09configuration space >>>> + *=09=09=09=09@buf: buffer used to write from >>>> + *=09=09=09=09@len: the length to write to >>>> + *=09=09=09=09configration space >>>> + * @get_generation:=09=09Get device config generaton (optional) >>>> + *=09=09=09=09@mdev: mediated device >>>> + *=09=09=09=09Returns u32: device generation >>>> + */ >>>> +struct mdev_virtio_device_ops { >>>> +=09/* Mdev device ops */ >>>> +=09u64 (*get_mdev_features)(struct mdev_device *mdev); >>>> +=09bool (*set_mdev_feature)(struct mdev_device *mdev); >>>> +=09/* Virtqueue ops */ >>>> +=09int (*set_vq_address)(struct mdev_device *mdev, >>>> +=09=09=09 u16 idx, u64 desc_area, u64 driver_area, >>>> +=09=09=09 u64 device_area); >>>> +=09void (*set_vq_num)(struct mdev_device *mdev, u16 idx, u32 num); >>>> +=09void (*kick_vq)(struct mdev_device *mdev, u16 idx); >>>> +=09void (*set_vq_cb)(struct mdev_device *mdev, u16 idx, >>>> +=09=09=09 struct virtio_mdev_callback *cb); >>>> +=09void (*set_vq_ready)(struct mdev_device *mdev, u16 idx, bool ready= ); >>>> +=09bool (*get_vq_ready)(struct mdev_device *mdev, u16 idx); >>>> +=09int (*set_vq_state)(struct mdev_device *mdev, u16 idx, u64 state); >>>> +=09u64 (*get_vq_state)(struct mdev_device *mdev, u16 idx); >>>> + >>>> +=09/* Virtio device ops */ >>>> +=09u16 (*get_vq_align)(struct mdev_device *mdev); >>>> +=09u64 (*get_features)(struct mdev_device *mdev); >>>> +=09int (*set_features)(struct mdev_device *mdev, u64 features); >>>> +=09void (*set_config_cb)(struct mdev_device *mdev, >>>> +=09=09=09 struct virtio_mdev_callback *cb); >>>> +=09u16 (*get_vq_num_max)(struct mdev_device *mdev); >>>> +=09u32 (*get_device_id)(struct mdev_device *mdev); >>>> +=09u32 (*get_vendor_id)(struct mdev_device *mdev); >>>> +=09u8 (*get_status)(struct mdev_device *mdev); >>>> +=09void (*set_status)(struct mdev_device *mdev, u8 status); >>>> +=09void (*get_config)(struct mdev_device *mdev, unsigned int offset, >>>> +=09=09=09 void *buf, unsigned int len); >>>> +=09void (*set_config)(struct mdev_device *mdev, unsigned int offset, >>>> +=09=09=09 const void *buf, unsigned int len); >>>> +=09u32 (*get_generation)(struct mdev_device *mdev); >>>> +}; >>>> + >>>> +void mdev_set_virtio_ops(struct mdev_device *mdev, >>>> +=09=09=09 const struct mdev_virtio_device_ops *virtio_ops); >>>> + >>>> +#endif