linux-kernel - Re: [PATCH v2 03/12] tee: add tee_shm_alloc_user

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Date:   Wed, 19 Jan 2022 08:36:08 +0100
From:   Jens Wiklander <jens.wiklander@...aro.org>
To:     Sumit Garg <sumit.garg@...aro.org>
Cc:     linux-kernel@...r.kernel.org, op-tee@...ts.trustedfirmware.org,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Devaraj Rangasamy <Devaraj.Rangasamy@....com>,
        Rijo Thomas <Rijo-john.Thomas@....com>,
        David Howells <dhowells@...hat.com>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>
Subject: Re: [PATCH v2 03/12] tee: add tee_shm_alloc_user_buf()

On Tue, Jan 18, 2022 at 2:11 PM Sumit Garg <sumit.garg@...aro.org> wrote:
>
> On Fri, 14 Jan 2022 at 20:38, Jens Wiklander <jens.wiklander@...aro.org> wrote:
> >
> > Adds a new function tee_shm_alloc_user_buf() or user mode allocations,
> > replacing passing the flags TEE_SHM_MAPPED | TEE_SHM_DMA_BUF to
> > tee_shm_alloc().
> >
> > Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
> > ---
> >  drivers/tee/tee_core.c     |  2 +-
> >  drivers/tee/tee_shm.c      | 18 ++++++++++++++++++
> >  drivers/tee/tee_shm_pool.c |  2 +-
> >  include/linux/tee_drv.h    |  3 ++-
> >  4 files changed, 22 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> > index 3fc426dad2df..a15812baaeb1 100644
> > --- a/drivers/tee/tee_core.c
> > +++ b/drivers/tee/tee_core.c
> > @@ -297,7 +297,7 @@ static int tee_ioctl_shm_alloc(struct tee_context *ctx,
> >         if (data.flags)
> >                 return -EINVAL;
> >
> > -       shm = tee_shm_alloc(ctx, data.size, TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
> > +       shm = tee_shm_alloc_user_buf(ctx, data.size);
>
> Since it's the only place this API would be used within the driver
> itself and I can't see any future usage from other kernel drivers..
>
> >         if (IS_ERR(shm))
> >                 return PTR_ERR(shm);
> >
> > diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> > index 499fccba3d74..b43178986985 100644
> > --- a/drivers/tee/tee_shm.c
> > +++ b/drivers/tee/tee_shm.c
> > @@ -127,6 +127,24 @@ struct tee_shm *tee_shm_alloc(struct tee_context *ctx, size_t size, u32 flags)
> >  }
> >  EXPORT_SYMBOL_GPL(tee_shm_alloc);
> >
> > +/**
> > + * tee_shm_alloc_user_buf() - Allocate shared memory for user space
> > + * @ctx:       Context that allocates the shared memory
> > + * @size:      Requested size of shared memory
> > + *
> > + * Memory allocated as user space shared memory is automatically freed when
> > + * the TEE file pointer is closed. The primary usage of this function is
> > + * when the TEE driver doesn't support registering ordinary user space
> > + * memory.
> > + *
> > + * @returns a pointer to 'struct tee_shm'
> > + */
> > +struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size)
> > +{
> > +       return tee_shm_alloc(ctx, size, TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
> > +}
> > +EXPORT_SYMBOL_GPL(tee_shm_alloc_user_buf);
> > +
>
> ..so I don't see any value-add for this export..
>
> >  /**
> >   * tee_shm_alloc_kernel_buf() - Allocate shared memory for kernel buffer
> >   * @ctx:       Context that allocates the shared memory
> > diff --git a/drivers/tee/tee_shm_pool.c b/drivers/tee/tee_shm_pool.c
> > index a9f9d50fd181..0e460347138a 100644
> > --- a/drivers/tee/tee_shm_pool.c
> > +++ b/drivers/tee/tee_shm_pool.c
> > @@ -1,6 +1,6 @@
> >  // SPDX-License-Identifier: GPL-2.0-only
> >  /*
> > - * Copyright (c) 2015, Linaro Limited
> > + * Copyright (c) 2015, 2017, 2022 Linaro Limited
> >   */
> >  #include <linux/device.h>
> >  #include <linux/dma-buf.h>
> > diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> > index 6b0f0d01ebdf..26b450484ac1 100644
> > --- a/include/linux/tee_drv.h
> > +++ b/include/linux/tee_drv.h
> > @@ -1,6 +1,6 @@
> >  /* SPDX-License-Identifier: GPL-2.0-only */
> >  /*
> > - * Copyright (c) 2015-2016, Linaro Limited
> > + * Copyright (c) 2015-2022 Linaro Limited
> >   */
> >
> >  #ifndef __TEE_DRV_H
> > @@ -308,6 +308,7 @@ void *tee_get_drvdata(struct tee_device *teedev);
> >   * @returns a pointer to 'struct tee_shm'
> >   */
> >  struct tee_shm *tee_shm_alloc(struct tee_context *ctx, size_t size, u32 flags);
> > +struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size);
>
> ..and it should rather belong to drivers/tee/tee_private.h.

Makes sense, I'll fix this in the next version.

Thanks,
Jens

>
> -Sumit
>
> >  struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size);
> >
> >  /**
> > --
> > 2.31.1
> >