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

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Date: Tue, 27 Feb 2024 10:56:13 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Andy Gross <agross@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Elliot Berman <quic_eberman@...cinc.com>, 
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Guru Das Srinagesh <quic_gurus@...cinc.com>, 
	Andrew Halaney <ahalaney@...hat.com>, Maximilian Luz <luzmaximilian@...il.com>, 
	Alex Elder <elder@...aro.org>, Srini Kandagatla <srinivas.kandagatla@...aro.org>, 
	Arnd Bergmann <arnd@...db.de>, linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, kernel@...cinc.com, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Deepti Jaggi <quic_djaggi@...cinc.com>
Subject: Re: [PATCH v7 10/12] firmware: qcom: tzmem: enable SHM Bridge support

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@...nel.org> wrote:
> >
> > On Mon, Feb 05, 2024 at 07:28:08PM +0100, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.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]