linux-kernel - Re: [RFC PATCH 4/4] dma-buf: heaps: add Linaro restricted dmabuf heap support

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Message-ID: <CABdmKX2Tsp-KG6_Lth7VUcZcxCfgbsBYqZ5N2h574J+sNP2SxA@mail.gmail.com>
Date: Tue, 10 Sep 2024 08:08:10 -0700
From: "T.J. Mercier" <tjmercier@...gle.com>
To: Jens Wiklander <jens.wiklander@...aro.org>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linaro-mm-sig@...ts.linaro.org, op-tee@...ts.trustedfirmware.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
	Olivier Masse <olivier.masse@....com>, Thierry Reding <thierry.reding@...il.com>, 
	Yong Wu <yong.wu@...iatek.com>, Sumit Semwal <sumit.semwal@...aro.org>, 
	Benjamin Gaignard <benjamin.gaignard@...labora.com>, Brian Starkey <Brian.Starkey@....com>, 
	John Stultz <jstultz@...gle.com>, Christian König <christian.koenig@....com>, 
	Sumit Garg <sumit.garg@...aro.org>, Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Subject: Re: [RFC PATCH 4/4] dma-buf: heaps: add Linaro restricted dmabuf heap support

On Mon, Sep 9, 2024 at 11:06 PM Jens Wiklander
<jens.wiklander@...aro.org> wrote:
>
> On Wed, Sep 4, 2024 at 11:42 PM T.J. Mercier <tjmercier@...gle.com> wrote:
> >
> > On Wed, Sep 4, 2024 at 2:44 AM Jens Wiklander <jens.wiklander@...aro.org> wrote:
> > >
> > > On Tue, Sep 3, 2024 at 7:50 PM T.J. Mercier <tjmercier@...gle.com> wrote:
> > > >
> > > > On Fri, Aug 30, 2024 at 12:04 AM Jens Wiklander
> > > > <jens.wiklander@...aro.org> wrote:
> > > > >
> > > > > Add a Linaro restricted heap using the linaro,restricted-heap bindings
> > > > > implemented based on the generic restricted heap.
> > > > >
> > > > > The bindings defines a range of physical restricted memory. The heap
> > > > > manages this address range using genalloc. The allocated dma-buf file
> > > > > descriptor can later be registered with the TEE subsystem for later use
> > > > > via Trusted Applications in the secure world.
> > > > >
> > > > > Co-developed-by: Olivier Masse <olivier.masse@....com>
> > > > > Signed-off-by: Olivier Masse <olivier.masse@....com>
> > > > > Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
> > > > > ---
> > > > >  drivers/dma-buf/heaps/Kconfig                 |  10 ++
> > > > >  drivers/dma-buf/heaps/Makefile                |   1 +
> > > > >  .../dma-buf/heaps/restricted_heap_linaro.c    | 165 ++++++++++++++++++
> > > > >  3 files changed, 176 insertions(+)
> > > > >  create mode 100644 drivers/dma-buf/heaps/restricted_heap_linaro.c
> > > > >
> > > > > diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
> > > > > index 58903bc62ac8..82e2c5d09242 100644
> > > > > --- a/drivers/dma-buf/heaps/Kconfig
> > > > > +++ b/drivers/dma-buf/heaps/Kconfig
> > > > > @@ -28,3 +28,13 @@ config DMABUF_HEAPS_RESTRICTED_MTK
> > > > >         help
> > > > >           Enable restricted dma-buf heaps for MediaTek platform. This heap is backed by
> > > > >           TEE client interfaces. If in doubt, say N.
> > > > > +
> > > > > +config DMABUF_HEAPS_RESTRICTED_LINARO
> > > > > +       bool "Linaro DMA-BUF Restricted Heap"
> > > > > +       depends on DMABUF_HEAPS_RESTRICTED
> > > > > +       help
> > > > > +         Choose this option to enable the Linaro restricted dma-buf heap.
> > > > > +         The restricted heap pools are defined according to the DT. Heaps
> > > > > +         are allocated in the pools using gen allocater.
> > > > > +         If in doubt, say N.
> > > > > +
> > > > > diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile
> > > > > index 0028aa9d875f..66b2f67c47b5 100644
> > > > > --- a/drivers/dma-buf/heaps/Makefile
> > > > > +++ b/drivers/dma-buf/heaps/Makefile
> > > > > @@ -2,4 +2,5 @@
> > > > >  obj-$(CONFIG_DMABUF_HEAPS_CMA)         += cma_heap.o
> > > > >  obj-$(CONFIG_DMABUF_HEAPS_RESTRICTED)  += restricted_heap.o
> > > > >  obj-$(CONFIG_DMABUF_HEAPS_RESTRICTED_MTK)      += restricted_heap_mtk.o
> > > > > +obj-$(CONFIG_DMABUF_HEAPS_RESTRICTED_LINARO)   += restricted_heap_linaro.o
> > > > >  obj-$(CONFIG_DMABUF_HEAPS_SYSTEM)      += system_heap.o
> > > > > diff --git a/drivers/dma-buf/heaps/restricted_heap_linaro.c b/drivers/dma-buf/heaps/restricted_heap_linaro.c
> > > > > new file mode 100644
> > > > > index 000000000000..4b08ed514023
> > > > > --- /dev/null
> > > > > +++ b/drivers/dma-buf/heaps/restricted_heap_linaro.c
> > > > > @@ -0,0 +1,165 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0
> > > > > +/*
> > > > > + * DMABUF secure heap exporter
> > > > > + *
> > > > > + * Copyright 2021 NXP.
> > > > > + * Copyright 2024 Linaro Limited.
> > > > > + */
> > > > > +
> > > > > +#define pr_fmt(fmt)     "rheap_linaro: " fmt
> > > > > +
> > > > > +#include <linux/dma-buf.h>
> > > > > +#include <linux/err.h>
> > > > > +#include <linux/genalloc.h>
> > > > > +#include <linux/module.h>
> > > > > +#include <linux/of.h>
> > > > > +#include <linux/of_fdt.h>
> > > > > +#include <linux/of_reserved_mem.h>
> > > > > +#include <linux/scatterlist.h>
> > > > > +#include <linux/slab.h>
> > > > > +
> > > > > +#include "restricted_heap.h"
> > > > > +
> > > > > +#define MAX_HEAP_COUNT 2
> > > >
> > > > Are multiple supported because of what Cyrille mentioned here about permissions?
> > > > https://lore.kernel.org/lkml/DBBPR04MB7514E006455AEA407041E4F788709@DBBPR04MB7514.eurprd04.prod.outlook.com/
> > >
> > > Yes, I kept that as is.
> >
> > Ok thanks.
> >
> > > > So this is just some arbitrary limit? I'd prefer to have some sort of
> > > > documentation about this.
> > >
> > > How about removing the limit and using dynamic allocation instead?
> >
> > That works too!
>
> It turns out that was easier said than done. The limit is hardcoded
> because dynamic memory allocation isn't available at that stage during
> boot. We have a short description of this heap in Kconfig. I'll add
> something about the limit there if that makes sense.
>
> Thanks,
> Jens

Ah ok sounds good.

I noticed one other thing, linaro_restricted_heap_init and add_heap
should probably have __init. Last week I sent a patch to add that for
the CMA and system heaps.