Re: [PATCH v3 13/15] firmware: qcom: tzmem: enable SHM Bridge support

[Bartosz Golaszewski]

On Fri, Oct 13, 2023 at 3:31 PM Andrew Halaney <ahalaney@xxxxxxxxxx> wrote:
>
> On Fri, Oct 13, 2023 at 10:32:00AM +0200, Bartosz Golaszewski wrote:
> > On Thu, Oct 12, 2023 at 12:17 AM Andrew Halaney <ahalaney@xxxxxxxxxx> wrote:
> > >
> > > On Wed, Oct 11, 2023 at 04:14:32PM -0500, Andrew Halaney wrote:
> > > > On Mon, Oct 09, 2023 at 05:34:25PM +0200, Bartosz Golaszewski wrote:
> > > > > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > > > >
> > > > > Add a new Kconfig option for selecting the SHM Bridge mode of operation
> > > > > for the TrustZone memory allocator.
> > > > >
> > > > > If enabled at build-time, it will still be checked for availability at
> > > > > run-time. If the architecture doesn't support SHM Bridge, the allocator
> > > > > will work just like in the default mode.
> > > > >
> > > > > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > > > > ---
> > > > >  drivers/firmware/qcom/Kconfig      | 10 +++++
> > > > >  drivers/firmware/qcom/qcom_tzmem.c | 67 +++++++++++++++++++++++++++++-
> > > > >  2 files changed, 76 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/firmware/qcom/Kconfig b/drivers/firmware/qcom/Kconfig
> > > > > index 237da40de832..e01407e31ae4 100644
> > > > > --- a/drivers/firmware/qcom/Kconfig
> > > > > +++ b/drivers/firmware/qcom/Kconfig
> > > > > @@ -27,6 +27,16 @@ config QCOM_TZMEM_MODE_DEFAULT
> > > > >       Use the default allocator mode. The memory is page-aligned, non-cachable
> > > > >       and contiguous.
> > > > >
> > > > > +config QCOM_TZMEM_MODE_SHMBRIDGE
> > > > > +   bool "SHM Bridge"
> > > > > +   help
> > > > > +     Use Qualcomm Shared Memory Bridge. The memory has the same alignment as
> > > > > +     in the 'Default' allocator but is also explicitly marked as an SHM Bridge
> > > > > +     buffer.
> > > > > +
> > > > > +     With this selected, all buffers passed to the TrustZone must be allocated
> > > > > +     using the TZMem allocator or else the TrustZone will refuse to use them.
> > > > > +
> > > > >  endchoice
> > > > >
> > > > >  config QCOM_SCM_DOWNLOAD_MODE_DEFAULT
> > > > > diff --git a/drivers/firmware/qcom/qcom_tzmem.c b/drivers/firmware/qcom/qcom_tzmem.c
> > > > > index eee51fed756e..b3137844fe43 100644
> > > > > --- a/drivers/firmware/qcom/qcom_tzmem.c
> > > > > +++ b/drivers/firmware/qcom/qcom_tzmem.c
> > > > > @@ -55,7 +55,72 @@ static void qcom_tzmem_cleanup_pool(struct qcom_tzmem_pool *pool)
> > > > >
> > > > >  }
> > > > >
> > > > > -#endif /* CONFIG_QCOM_TZMEM_MODE_DEFAULT */
> > > > > +#elif IS_ENABLED(CONFIG_QCOM_TZMEM_MODE_SHMBRIDGE)
> > > > > +
> > > > > +#include <linux/firmware/qcom/qcom_scm.h>
> > > > > +
> > > > > +#define QCOM_SHM_BRIDGE_NUM_VM_SHIFT 9
> > > > > +
> > > > > +static bool qcom_tzmem_using_shm_bridge;
> > > > > +
> > > > > +static int qcom_tzmem_init(void)
> > > > > +{
> > > > > +   int ret;
> > > > > +
> > > > > +   ret = qcom_scm_shm_bridge_enable();
> > > > > +   if (ret == -EOPNOTSUPP) {
> > > > > +           dev_info(qcom_tzmem_dev, "SHM Bridge not supported\n");
> > > > > +           ret = 0;
> > > > > +   }
> > > > > +
> > > > > +   if (!ret)
> > > > > +           qcom_tzmem_using_shm_bridge = true;
> > > >
> > > > Does the qcom_scm_shm_bridge_enable() returning -EOPNOTSUPP case make
> > > > sense? Setting ret to 0 and then claiming we're using shm_bridge seems
> > > > wrong to me.
> > > >
> >
> > You answered yourself in the previous email. The size cannot be less
> > than 4096 bytes. There's no need to check it anymore than that IMO.
> >
>
> Ok, I still think that would be nice but your call.
>
> But this comment was about the above ret = 0 assignment. I am thinking
> that's incorrect, because you fail to enable SHM bridge with
> -EOPNOTSUPP, then you go ahead and tell the code to claim it is
> supported with the if (!ret) conditional. This results in SHM bridge
> trying to be used when its really not supported right?
>
> Looks to me that you're really trying to return 0, not ret = 0.
>

Gah! You're right, I should have waited with v4. Oh well, I'll respin
it next week.

Bart

> > Bart
> >
> > > > > +
> > > > > +   return ret;
> > > > > +}
> > > > > +
> > > > > +static int qcom_tzmem_init_pool(struct qcom_tzmem_pool *pool)
> > > > > +{
> > > > > +   u64 pfn_and_ns_perm, ipfn_and_s_perm, size_and_flags, ns_perms, *handle;
> > > > > +   int ret;
> > > > > +
> > > > > +   if (!qcom_tzmem_using_shm_bridge)
> > > > > +           return 0;
> > > > > +
> > > > > +   ns_perms = (QCOM_SCM_PERM_WRITE | QCOM_SCM_PERM_READ);
> > > > > +   pfn_and_ns_perm = (u64)pool->pbase | ns_perms;
> > > > > +   ipfn_and_s_perm = (u64)pool->pbase | ns_perms;
> > > > > +   size_and_flags = pool->size | (1 << QCOM_SHM_BRIDGE_NUM_VM_SHIFT);
> > > >
> > > > Is there any sanity checking that can be done here? I assume bits 0-11 are all
> > > > flag fields (or at least unrelated to size which I assume at a minimum
> > > > must be 4k aka bit 12).
> > >
> > > I guess qcom_tzmem_pool_new's PAGE_ALIGN would make sure this is
> > > probably ok for all future users, but I do think some sanity would be
> > > nice to indicate the size's allowed for SHM bridge.
> > >
> > > >
> > > > > +
> > > > > +   handle = kzalloc(sizeof(*handle), GFP_KERNEL);
> > > >
> > > > Consider __free(kfree) + return_ptr() usage?
> > > >
> > > > > +   if (!handle)
> > > > > +           return -ENOMEM;
> > > > > +
> > > > > +   ret = qcom_scm_shm_bridge_create(qcom_tzmem_dev, pfn_and_ns_perm,
> > > > > +                                    ipfn_and_s_perm, size_and_flags,
> > > > > +                                    QCOM_SCM_VMID_HLOS, handle);
> > > > > +   if (ret) {
> > > > > +           kfree(handle);
> > > > > +           return ret;
> > > > > +   }
> > > > > +
> > > > > +   pool->priv = handle;
> > > > > +
> > > > > +   return 0;
> > > > > +}
> > > > > +
> > > > > +static void qcom_tzmem_cleanup_pool(struct qcom_tzmem_pool *pool)
> > > > > +{
> > > > > +   u64 *handle = pool->priv;
> > > > > +
> > > > > +   if (!qcom_tzmem_using_shm_bridge)
> > > > > +           return;
> > > > > +
> > > > > +   qcom_scm_shm_bridge_delete(qcom_tzmem_dev, *handle);
> > > > > +   kfree(handle);
> > > > > +}
> > > > > +
> > > > > +#endif /* CONFIG_QCOM_TZMEM_MODE_SHMBRIDGE */
> > > > >
> > > > >  /**
> > > > >   * qcom_tzmem_pool_new() - Create a new TZ memory pool.
> > > > > --
> > > > > 2.39.2
> > > > >
> > >
> >
>