On Fri, Sep 11, 2020 at 09:46:56AM +0200, Guennadi Liakhovetski wrote: > Hi Mathieu, > > On Thu, Sep 10, 2020 at 11:22:11AM -0600, Mathieu Poirier wrote: > > Good morning Guennadi, > > > > On Thu, Sep 10, 2020 at 10:38:54AM +0200, Guennadi Liakhovetski wrote: > > > Hi Mathieu, > > > > > > On Wed, Sep 09, 2020 at 04:39:46PM -0600, Mathieu Poirier wrote: > > > > Good afternoon, > > > > > > > > On Wed, Aug 26, 2020 at 07:46:36PM +0200, Guennadi Liakhovetski wrote: > > > > > Linux supports running the RPMsg protocol over the VirtIO transport > > > > > protocol, but currently there is only support for VirtIO clients and > > > > > no support for a VirtIO server. This patch adds a vhost-based RPMsg > > > > > server implementation. > > > > > > > > This changelog is very confusing... At this time the name service in the > > > > remoteproc space runs as a server on the application processor. But from the > > > > above the remoteproc usecase seems to be considered to be a client > > > > configuration. > > > > > > I agree that this isn't very obvious. But I think it is common to call the > > > host "a server" and guests "clients." E.g. in vhost.c in the top-of-thefile > > > comment: > > > > Ok - that part we agree on. > > > > > > > > * Generic code for virtio server in host kernel. > > > > > > I think the generic concept behind this notation is, that as guests boot, > > > they send their requests to the host, e.g. VirtIO device drivers on guests > > > send requests over VirtQueues to VirtIO servers on the host, which can run > > > either in the user- or in the kernel-space. And I think you can follow that > > > > I can see that process taking place. After all virtIO devices on guests are > > only stubs that need host support for access to HW. > > > > > logic in case of devices or remote processors too: it's the main CPU(s) > > > that boot(s) and start talking to devices and remote processors, so in that > > > sence devices are servers and the CPUs are their clients. > > > > In the remote processor case, the remoteproc core (application processor) sets up > > the name service but does not initiate the communication with a remote > > processor. It simply waits there for a name space request to come in from the > > remote processor. > > Hm, I don't see that in two examples, that I looked at: mtk and virtio. In both > cases the announcement seems to be directly coming from the application processor > maybe after some initialisation. > Can you expand on that part - perhaps point me to the (virtio) code you are referring to? > > > And yes, the name-space announcement use-case seems confusing to me too - it > > > reverts the relationship in a way: once a guest has booted and established > > > connections to any rpmsg "devices," those send their namespace announcements > > > back. But I think this can be regarded as server identification: you connect > > > to a server and it replies with its identification and capabilities. > > > > Based on the above can I assume vhost_rpmsg_ns_announce() is sent from the > > guest? > > No, it's "vhost_..." so it's running on the host. Ok, that's better and confirms the usage of the VIRTIO_RPMSG_RESPONSE queue. When reading your explanation above, I thought the term "those" referred to the guest. In light of your explanation I now understand that "those" referred to the rpmgs devices on the host. In the above paragraph you write: ... "once a guest has booted and established connections to any rpmsg "devices", those send their namespace announcements back". I'd like to unpack a few things about this sentence: 1) In this context, how is a "connection" established between a guest and a host? 2) How does the guest now about the rpmsg devices it has made a connection to? 3) Why is a namespace announcement needed at all when guests are aware of the rpmsg devices instantiated on the host, and have already connected to them? > The host (the server, an > analogue of the application processor, IIUC) sends NS announcements to guests. I think we have just found the source of the confusion - in the remoteproc world the application processor receives name announcements, it doesn't send them. > > > I saw your V7, something I will look into. In the mean time I need to bring > > your attention to this set [1] from Arnaud. Please have a look as it will > > impact your work. > > > > https://patchwork.kernel.org/project/linux-remoteproc/list/?series=338335 > > Yes, I've had a look at that series, thanks for forwarding it to me. TBH I > don't quite understand some choices there, e.g. creating a separate driver and > then having to register devices just for the namespace announcement. I don't > think creating virtual devices is taken easily in Linux. But either way I > don't think our series conflict a lot, but I do hope that I can merge my > series first, he'd just have to switch to using the header, that I'm adding. > Hardly too many changes otherwise. It is not the conflicts between the series that I wanted to highlight but the fact that name service is in the process of becoming a driver on its own, and with no dependence on the transport mechanism. > > > > > And I don't see a server implementation per se... It is more like a client > > > > implementation since vhost_rpmsg_announce() uses the RESPONSE queue, which sends > > > > messages from host to guest. > > > > > > > > Perhaps it is my lack of familiarity with vhost terminology. > > > > > > > > > > > > > > Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@xxxxxxxxxxxxxxx> > > > > > --- > > > > > drivers/vhost/Kconfig | 7 + > > > > > drivers/vhost/Makefile | 3 + > > > > > drivers/vhost/rpmsg.c | 373 ++++++++++++++++++++++++++++++++++++ > > > > > drivers/vhost/vhost_rpmsg.h | 74 +++++++ > > > > > 4 files changed, 457 insertions(+) > > > > > create mode 100644 drivers/vhost/rpmsg.c > > > > > create mode 100644 drivers/vhost/vhost_rpmsg.h > > > > > > > > > > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig > > > > > index 587fbae06182..046b948fc411 100644 > > > > > --- a/drivers/vhost/Kconfig > > > > > +++ b/drivers/vhost/Kconfig > > > > > @@ -38,6 +38,13 @@ config VHOST_NET > > > > > To compile this driver as a module, choose M here: the module will > > > > > be called vhost_net. > > > > > > > > > > +config VHOST_RPMSG > > > > > + tristate > > > > > + select VHOST > > > > > + help > > > > > + Vhost RPMsg API allows vhost drivers to communicate with VirtIO > > > > > + drivers, using the RPMsg over VirtIO protocol. > > > > > > > > I had to assume vhost drivers are running on the host and virtIO drivers on the > > > > guests. This may be common knowledge for people familiar with vhosts but > > > > certainly obscur for commoners Having a help section that is clear on what is > > > > happening would remove any ambiguity. > > > > > > It is the terminology, yes, but you're right, the wording isn't very clear, will > > > improve. > > > > > > > > + > > > > > config VHOST_SCSI > > > > > tristate "VHOST_SCSI TCM fabric driver" > > > > > depends on TARGET_CORE && EVENTFD > > > > > diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile > > > > > index f3e1897cce85..9cf459d59f97 100644 > > > > > --- a/drivers/vhost/Makefile > > > > > +++ b/drivers/vhost/Makefile > > > > > @@ -2,6 +2,9 @@ > > > > > obj-$(CONFIG_VHOST_NET) += vhost_net.o > > > > > vhost_net-y := net.o > > > > > > > > > > +obj-$(CONFIG_VHOST_RPMSG) += vhost_rpmsg.o > > > > > +vhost_rpmsg-y := rpmsg.o > > > > > + > > > > > obj-$(CONFIG_VHOST_SCSI) += vhost_scsi.o > > > > > vhost_scsi-y := scsi.o > > > > > > > > > > diff --git a/drivers/vhost/rpmsg.c b/drivers/vhost/rpmsg.c > > > > > new file mode 100644 > > > > > index 000000000000..c26d7a4afc6d > > > > > --- /dev/null > > > > > +++ b/drivers/vhost/rpmsg.c > > > > > @@ -0,0 +1,373 @@ > > > > > +// SPDX-License-Identifier: GPL-2.0-only > > > > > +/* > > > > > + * Copyright(c) 2020 Intel Corporation. All rights reserved. > > > > > + * > > > > > + * Author: Guennadi Liakhovetski <guennadi.liakhovetski@xxxxxxxxxxxxxxx> > > > > > + * > > > > > + * Vhost RPMsg VirtIO interface. It provides a set of functions to match the > > > > > + * guest side RPMsg VirtIO API, provided by drivers/rpmsg/virtio_rpmsg_bus.c > > > > > > > > Again, very confusing. The changelog refers to a server implementation but to > > > > me this refers to a client implementation, especially if rpmsg_recv_single() and > > > > rpmsg_ns_cb() are used on the other side of the pipe. > > > > > > I think the above is correct. "Vhost" indicates, that this is running on the host. > > > "match the guest side" means, that you can use this API on the host and it is > > > designed to work together with the RPMsg VirtIO drivers running on guests, as > > > implemented *on guests* by virtio_rpmsg_bus.c. Would "to work together" be a better > > > description than "to match?" > > > > Lets forget about this part now and concentrate on the above conversation. > > Things will start to make sense at one point. > > I've improved that description a bit, it was indeed rather clumsy. Much appreciated - I'll take a look a V7 next week. > > [snip] > > > > > > diff --git a/drivers/vhost/vhost_rpmsg.h b/drivers/vhost/vhost_rpmsg.h > > > > > new file mode 100644 > > > > > index 000000000000..30072cecb8a0 > > > > > --- /dev/null > > > > > +++ b/drivers/vhost/vhost_rpmsg.h > > > > > @@ -0,0 +1,74 @@ > > > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > > > +/* > > > > > + * Copyright(c) 2020 Intel Corporation. All rights reserved. > > > > > + * > > > > > + * Author: Guennadi Liakhovetski <guennadi.liakhovetski@xxxxxxxxxxxxxxx> > > > > > + */ > > > > > + > > > > > +#ifndef VHOST_RPMSG_H > > > > > +#define VHOST_RPMSG_H > > > > > + > > > > > +#include <linux/uio.h> > > > > > +#include <linux/virtio_rpmsg.h> > > > > > + > > > > > +#include "vhost.h" > > > > > + > > > > > +/* RPMsg uses two VirtQueues: one for each direction */ > > > > > +enum { > > > > > + VIRTIO_RPMSG_RESPONSE, /* RPMsg response (host->guest) buffers */ > > > > > + VIRTIO_RPMSG_REQUEST, /* RPMsg request (guest->host) buffers */ > > > > > + /* Keep last */ > > > > > + VIRTIO_RPMSG_NUM_OF_VQS, > > > > > +}; > > > > > + > > > > > +struct vhost_rpmsg_ept; > > > > > + > > > > > +struct vhost_rpmsg_iter { > > > > > + struct iov_iter iov_iter; > > > > > + struct rpmsg_hdr rhdr; > > > > > + struct vhost_virtqueue *vq; > > > > > + const struct vhost_rpmsg_ept *ept; > > > > > + int head; > > > > > + void *priv; > > > > > > > > I don't see @priv being used anywhere. > > > > > > That's logical: this is a field, private to the API users, so the core shouldn't > > > use it :-) It's used in later patches. > > > > That is where structure documentation is useful. I will let Michael decide what > > he wants to do. > > I can add some kerneldoc documentation there, no problem. > > > Thanks for the feedback, > > Thanks for your reviews! I'd very much like to close all the still open points > and merge the series ASAP. > > Thanks > Guennadi > > > Mathieu > > > > > > > > > > > > > > +}; > > > > > + > > > > > +struct vhost_rpmsg { > > > > > + struct vhost_dev dev; > > > > > + struct vhost_virtqueue vq[VIRTIO_RPMSG_NUM_OF_VQS]; > > > > > + struct vhost_virtqueue *vq_p[VIRTIO_RPMSG_NUM_OF_VQS]; > > > > > + const struct vhost_rpmsg_ept *ept; > > > > > + unsigned int n_epts; > > > > > +}; > > > > > + > > > > > +struct vhost_rpmsg_ept { > > > > > + ssize_t (*read)(struct vhost_rpmsg *, struct vhost_rpmsg_iter *); > > > > > + ssize_t (*write)(struct vhost_rpmsg *, struct vhost_rpmsg_iter *); > > > > > + int addr; > > > > > +}; > > > > > + > > > > > +static inline size_t vhost_rpmsg_iter_len(const struct vhost_rpmsg_iter *iter) > > > > > +{ > > > > > + return iter->rhdr.len; > > > > > +} > > > > > > > > Again, I don't see where this is used. > > > > > > This is exported API, it's used by users. > > > > > > > > + > > > > > +#define VHOST_RPMSG_ITER(_vq, _src, _dst) { \ > > > > > + .rhdr = { \ > > > > > + .src = cpu_to_vhost32(_vq, _src), \ > > > > > + .dst = cpu_to_vhost32(_vq, _dst), \ > > > > > + }, \ > > > > > + } > > > > > > > > Same. > > > > > > ditto. > > > > > > Thanks > > > Guennadi > > > > > > > Thanks, > > > > Mathieu > > > > > > > > > + > > > > > +void vhost_rpmsg_init(struct vhost_rpmsg *vr, const struct vhost_rpmsg_ept *ept, > > > > > + unsigned int n_epts); > > > > > +void vhost_rpmsg_destroy(struct vhost_rpmsg *vr); > > > > > +int vhost_rpmsg_ns_announce(struct vhost_rpmsg *vr, const char *name, > > > > > + unsigned int src); > > > > > +int vhost_rpmsg_start_lock(struct vhost_rpmsg *vr, > > > > > + struct vhost_rpmsg_iter *iter, > > > > > + unsigned int qid, ssize_t len); > > > > > +size_t vhost_rpmsg_copy(struct vhost_rpmsg *vr, struct vhost_rpmsg_iter *iter, > > > > > + void *data, size_t size); > > > > > +int vhost_rpmsg_finish_unlock(struct vhost_rpmsg *vr, > > > > > + struct vhost_rpmsg_iter *iter); > > > > > + > > > > > +#endif > > > > > -- > > > > > 2.28.0 > > > > >
