Re: [PATCH v5 8/8] firmware: tee_bnxt: Release TEE shm, session, and context during kexec

* Re: [PATCH v5 8/8] firmware: tee_bnxt: Release TEE shm, session, and context during kexec
       [not found] <20210716022332.GC3232@sequoia>
@ 2021-07-16  2:56 ` Vikas Gupta
       [not found] ` <CAHLZf_t5U1bh1H8sULbJz7xrZ-r3Dcmxuw9MMmG2fehS3C72uQ@mail.gmail.com>
  1 sibling, 0 replies; 7+ messages in thread
From: Vikas Gupta @ 2021-07-16  2:56 UTC (permalink / raw)
  To: Jens Wiklander, Allen Pais, Sumit Garg, Peter Huewe,
	Jarkko Sakkinen, Jason Gunthorpe, Vikas Gupta, Tyler Hicks
  Cc: Thirupathaiah Annapureddy, Pavel Tatashin,
	Rafał Miłecki, op-tee, linux-integrity,
	BCM Kernel Feedback, linux-mips, linux-kernel

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Hi Tyler/Allen,
 The patch looks good to me.

Thanks,
Vikas

> > From: Allen Pais <apais@linux.microsoft.com>
> >
> > Implement a .shutdown hook that will be called during a kexec operation
> > so that the TEE shared memory, session, and context that were set up
> > during .probe can be properly freed/closed.
> >
> > Additionally, don't use dma-buf backed shared memory for the
> > fw_shm_pool. dma-buf backed shared memory cannot be reliably freed and
> > unregistered during a kexec operation even when tee_shm_free() is called
> > on the shm from a .shutdown hook. The problem occurs because
> > dma_buf_put() calls fput() which then uses task_work_add(), with the
> > TWA_RESUME parameter, to queue tee_shm_release() to be called before the
> > current task returns to user mode. However, the current task never
> > returns to user mode before the kexec completes so the memory is never
> > freed nor unregistered.
> >
> > Use tee_shm_alloc_kernel_buf() to avoid dma-buf backed shared memory
> > allocation so that tee_shm_free() can directly call tee_shm_release().
> > This will ensure that the shm can be freed and unregistered during a
> > kexec operation.
> >
> > Fixes: 246880958ac9 ("firmware: broadcom: add OP-TEE based BNXT f/w manager")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Allen Pais <apais@linux.microsoft.com>
> > Co-developed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> > Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> > ---
> >  drivers/firmware/broadcom/tee_bnxt_fw.c | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/firmware/broadcom/tee_bnxt_fw.c b/drivers/firmware/broadcom/tee_bnxt_fw.c
> > index ed10da5313e8..a5bf4c3f6dc7 100644
> > --- a/drivers/firmware/broadcom/tee_bnxt_fw.c
> > +++ b/drivers/firmware/broadcom/tee_bnxt_fw.c
> > @@ -212,10 +212,9 @@ static int tee_bnxt_fw_probe(struct device *dev)
> >
> >       pvt_data.dev = dev;
> >
> > -     fw_shm_pool = tee_shm_alloc(pvt_data.ctx, MAX_SHM_MEM_SZ,
> > -                                 TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
> > +     fw_shm_pool = tee_shm_alloc_kernel_buf(pvt_data.ctx, MAX_SHM_MEM_SZ);
> >       if (IS_ERR(fw_shm_pool)) {
> > -             dev_err(pvt_data.dev, "tee_shm_alloc failed\n");
> > +             dev_err(pvt_data.dev, "tee_shm_alloc_kernel_buf failed\n");
> >               err = PTR_ERR(fw_shm_pool);
> >               goto out_sess;
> >       }
> > @@ -242,6 +241,14 @@ static int tee_bnxt_fw_remove(struct device *dev)
> >       return 0;
> >  }
> >
> > +static void tee_bnxt_fw_shutdown(struct device *dev)
> > +{
> > +     tee_shm_free(pvt_data.fw_shm_pool);
> > +     tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
> > +     tee_client_close_context(pvt_data.ctx);
> > +     pvt_data.ctx = NULL;
> > +}
> > +
> >  static const struct tee_client_device_id tee_bnxt_fw_id_table[] = {
> >       {UUID_INIT(0x6272636D, 0x2019, 0x0716,
> >                   0x42, 0x43, 0x4D, 0x5F, 0x53, 0x43, 0x48, 0x49)},
> > @@ -257,6 +264,7 @@ static struct tee_client_driver tee_bnxt_fw_driver = {
> >               .bus            = &tee_bus_type,
> >               .probe          = tee_bnxt_fw_probe,
> >               .remove         = tee_bnxt_fw_remove,
> > +             .shutdown       = tee_bnxt_fw_shutdown,
> >       },
> >  };
> >
> > --
> > 2.25.1
> >
>
> ----- End forwarded message -----

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