Re: [PATCH v6 05/10] tee: implement restricted DMA-heap

[Sumit Garg <sumit.garg@kernel.org>]

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On Tue, Apr 01, 2025 at 10:33:04AM +0200, Jens Wiklander wrote:
> On Tue, Apr 1, 2025 at 9:58 AM Sumit Garg <sumit.garg@kernel.org> wrote:
> >
> > On Tue, Mar 25, 2025 at 11:55:46AM +0100, Jens Wiklander wrote:
> > > Hi Sumit,
> > >
> >
> > <snip>
> >
> > >
> > > >
> > > > > +
> > > > > +#include "tee_private.h"
> > > > > +
> > > > > +struct tee_dma_heap {
> > > > > +     struct dma_heap *heap;
> > > > > +     enum tee_dma_heap_id id;
> > > > > +     struct tee_rstmem_pool *pool;
> > > > > +     struct tee_device *teedev;
> > > > > +     /* Protects pool and teedev above */
> > > > > +     struct mutex mu;
> > > > > +};
> > > > > +
> > > > > +struct tee_heap_buffer {
> > > > > +     struct tee_rstmem_pool *pool;
> > > > > +     struct tee_device *teedev;
> > > > > +     size_t size;
> > > > > +     size_t offs;
> > > > > +     struct sg_table table;
> > > > > +};
> > > > > +
> > > > > +struct tee_heap_attachment {
> > > > > +     struct sg_table table;
> > > > > +     struct device *dev;
> > > > > +};
> > > > > +
> > > > > +struct tee_rstmem_static_pool {
> > > > > +     struct tee_rstmem_pool pool;
> > > > > +     struct gen_pool *gen_pool;
> > > > > +     phys_addr_t pa_base;
> > > > > +};
> > > > > +
> > > > > +#if !IS_MODULE(CONFIG_TEE) && IS_ENABLED(CONFIG_DMABUF_HEAPS)
> > > >
> > > > Can this dependency rather be better managed via Kconfig?
> > >
> > > This was the easiest yet somewhat flexible solution I could find. If
> > > you have something better, let's use that instead.
> > >
> >
> > --- a/drivers/tee/optee/Kconfig
> > +++ b/drivers/tee/optee/Kconfig
> > @@ -5,6 +5,7 @@ config OPTEE
> >         depends on HAVE_ARM_SMCCC
> >         depends on MMU
> >         depends on RPMB || !RPMB
> > +       select DMABUF_HEAPS
> >         help
> >           This implements the OP-TEE Trusted Execution Environment (TEE)
> >           driver.
> 
> I wanted to avoid that since there are plenty of use cases where
> DMABUF_HEAPS aren't needed.

Yeah, but how the users will figure out the dependency to enable DMA
heaps with TEE subsystem. So it's better we provide a generic kernel
Kconfig which enables all the default features.

> This seems to do the job:
> +config TEE_DMABUF_HEAP
> + bool
> + depends on TEE = y && DMABUF_HEAPS
> 
> We can only use DMABUF_HEAPS if the TEE subsystem is compiled into the kernel.

Ah, I see. So we aren't exporting the DMA heaps APIs for TEE subsystem
to use. We should do that such that there isn't a hard dependency to
compile them into the kernel. 

-Sumit

> 
> Cheers,
> Jens