Re: [PATCH v7 10/12] firmware: qcom: tzmem: enable SHM Bridge support

Bjorn Andersson
2024-02-27T16:56:16Z

On Thu, Feb 22, 2024 at 05:24:19PM +0100, Bartosz Golaszewski wrote:
> On Sun, Feb 18, 2024 at 4:41 AM Bjorn Andersson <andersson@kernel.org> wrote:
> >
> > On Mon, Feb 05, 2024 at 07:28:08PM +0100, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > >
>
> [snip]
>
> > >
> > > +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.
> >
> > It's funny how this is the only place in the whole series I can find
> > this mentioned. One could from this statement guess that the eluding
> > scminvoke requires shmbridge and that this patch series exists solely
> > to facilitate the requirement stated in this paragraph.
> >
>
> Yes, scminvoke *requires* SHM bridge. So does the wrapped key support.
> No, this is not the only reason as - as stated by Srini - it improves
> overall safety of the system for all users.
>
> > Either this guess is correct and this should have been made clear in
> > the commit messages, or I'm guessing wrong here, in which case I need
> > some help to figure out why this series exists.
> >
>
> This series exists and IMO should get upstream soon to facilitate
> adding new security features (in addition to improving existing ones).

This needs to be stated in the cover letter/commit messages.

> As there are at least two such features in development (mentioned
> above) pushing this series upstream will make it easier to develop
> them independently.
>

Show me the work-in-progress code and I will entertain this argument.

Regards,
Bjorn

> Bart
>
> [snip]