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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Arnaud POULIQUEN <arnaud.pouliquen@st.com>,
	Alexander Lobakin <alobakin@pm.me>, Amit Shah <amit@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Suman Anna <s-anna@ti.com>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Ohad Ben-Cohen <ohad@wizery.com>,
	Jason Wang <jasowang@redhat.com>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"linux-remoteproc@vger.kernel.org"
	<linux-remoteproc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH virtio] virtio: virtio_console: fix DMA memory allocation for rproc serial
Date: Wed, 18 Nov 2020 05:16:15 -0500	[thread overview]
Message-ID: <20201118042039-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20201117140230.GA30567@infradead.org>

On Tue, Nov 17, 2020 at 02:02:30PM +0000, Christoph Hellwig wrote:
> On Tue, Nov 17, 2020 at 03:00:32PM +0100, Arnaud POULIQUEN wrote:
> > The dma_declare_coherent_memory allows to associate vdev0buffer memory region
> > to the remoteproc virtio device (vdev parent). This region is used to allocated
> > the rpmsg buffers.
> > The memory for the rpmsg buffer is allocated by the rpmsg_virtio device in
> > rpmsg_virtio_bus[1]. The size depends on the total size needed for the rpmsg
> > buffers.
> > 
> > The vrings are allocated directly by the remoteproc device.
> 
> Weird.  I thought virtio was pretty strict in not allowing diret DMA
> API usage in drivers to support the legacy no-mapping case.

Well remoteproc is weird in that it's use of DMA API precedes
standartization efforts, and it was never standardized in the virtio
spec ..

> Either way, the point stands:  if you want these magic buffers handed
> out to specific rpmsg instances I think not having to detour through the
> DMA API is going to make everyones life easier.


WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Ohad Ben-Cohen <ohad@wizery.com>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>, Amit Shah <amit@kernel.org>,
	Alexander Lobakin <alobakin@pm.me>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Arnaud POULIQUEN <arnaud.pouliquen@st.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	"linux-remoteproc@vger.kernel.org"
	<linux-remoteproc@vger.kernel.org>, Suman Anna <s-anna@ti.com>,
	"virtualization@lists.linux-foundation.org"
	<virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH virtio] virtio: virtio_console: fix DMA memory allocation for rproc serial
Date: Wed, 18 Nov 2020 05:16:15 -0500	[thread overview]
Message-ID: <20201118042039-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20201117140230.GA30567@infradead.org>

On Tue, Nov 17, 2020 at 02:02:30PM +0000, Christoph Hellwig wrote:
> On Tue, Nov 17, 2020 at 03:00:32PM +0100, Arnaud POULIQUEN wrote:
> > The dma_declare_coherent_memory allows to associate vdev0buffer memory region
> > to the remoteproc virtio device (vdev parent). This region is used to allocated
> > the rpmsg buffers.
> > The memory for the rpmsg buffer is allocated by the rpmsg_virtio device in
> > rpmsg_virtio_bus[1]. The size depends on the total size needed for the rpmsg
> > buffers.
> > 
> > The vrings are allocated directly by the remoteproc device.
> 
> Weird.  I thought virtio was pretty strict in not allowing diret DMA
> API usage in drivers to support the legacy no-mapping case.

Well remoteproc is weird in that it's use of DMA API precedes
standartization efforts, and it was never standardized in the virtio
spec ..

> Either way, the point stands:  if you want these magic buffers handed
> out to specific rpmsg instances I think not having to detour through the
> DMA API is going to make everyones life easier.

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

  reply	other threads:[~2020-11-18 10:16 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-04 15:31 [PATCH virtio] virtio: virtio_console: fix DMA memory allocation for rproc serial Alexander Lobakin
2020-11-04 18:21 ` Mathieu Poirier
2020-11-05  3:10 ` Jason Wang
2020-11-05  3:10   ` Jason Wang
2020-11-05 12:22   ` Alexander Lobakin
2020-11-09  6:04     ` Jason Wang
2020-11-09  6:04       ` Jason Wang
2020-11-16  9:19 ` Christoph Hellwig
2020-11-16  9:19   ` Christoph Hellwig
2020-11-16  9:51   ` Michael S. Tsirkin
2020-11-16  9:51     ` Michael S. Tsirkin
2020-11-16 16:27     ` Christoph Hellwig
2020-11-16 16:27       ` Christoph Hellwig
2020-11-16 16:43       ` Alexander Lobakin
2020-11-16 10:46   ` Arnaud POULIQUEN
2020-11-16 10:46     ` Arnaud POULIQUEN
2020-11-16 16:28     ` Christoph Hellwig
2020-11-16 16:28       ` Christoph Hellwig
2020-11-16 16:39       ` Christoph Hellwig
2020-11-16 16:39         ` Christoph Hellwig
2020-11-17 14:00         ` Arnaud POULIQUEN
2020-11-17 14:00           ` Arnaud POULIQUEN
2020-11-17 14:02           ` Christoph Hellwig
2020-11-17 14:02             ` Christoph Hellwig
2020-11-18 10:16             ` Michael S. Tsirkin [this message]
2020-11-18 10:16               ` Michael S. Tsirkin
2020-11-16 12:25   ` Michael S. Tsirkin
2020-11-16 12:25     ` Michael S. Tsirkin
2020-11-16 13:07     ` Alexander Lobakin
2020-11-16 13:12       ` Michael S. Tsirkin
2020-11-16 13:12         ` Michael S. Tsirkin
2020-11-16 16:30       ` Christoph Hellwig
2020-11-16 16:30         ` Christoph Hellwig
2020-12-28 18:54 ` patchwork-bot+linux-remoteproc

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