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

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Message-ID: <CAHLZf_tpwnE8X8BL4GnhFQMzhh+395qjAdGrxjeM-wGtZ_snCQ@mail.gmail.com>
Date:   Fri, 16 Jul 2021 08:26:06 +0530
From:   Vikas Gupta <vikas.gupta@...adcom.com>
To:     Jens Wiklander <jens.wiklander@...aro.org>,
        Allen Pais <apais@...ux.microsoft.com>,
        Sumit Garg <sumit.garg@...aro.org>,
        Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Vikas Gupta <vikas.gupta@...adcom.com>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>
Cc:     Thirupathaiah Annapureddy <thiruan@...rosoft.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Rafał Miłecki <zajec5@...il.com>,
        op-tee@...ts.trustedfirmware.org, linux-integrity@...r.kernel.org,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 8/8] firmware: tee_bnxt: Release TEE shm, session, and
 context during kexec

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

Thanks,
Vikas


> > From: Allen Pais <apais@...ux.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@...r.kernel.org
> > Signed-off-by: Allen Pais <apais@...ux.microsoft.com>
> > Co-developed-by: Tyler Hicks <tyhicks@...ux.microsoft.com>
> > Signed-off-by: Tyler Hicks <tyhicks@...ux.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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