linux-kernel - Re: [PATCH v10 13/15] firmware: qcom: scm: clarify the comment in qcom_scm_pas_init

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Date: Fri, 21 Jun 2024 15:42:40 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Elliot Berman <quic_eberman@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Robert Marko <robimarko@...il.com>, Das Srinagesh <quic_gurus@...cinc.com>, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Maximilian Luz <luzmaximilian@...il.com>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Srini Kandagatla <srinivas.kandagatla@...aro.org>, Arnd Bergmann <arnd@...db.de>, 
	Alex Elder <elder@...nel.org>, linux-arm-msm@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, kernel@...cinc.com, 
	Andrew Halaney <ahalaney@...hat.com>, Deepti Jaggi <quic_djaggi@...cinc.com>
Subject: Re: [PATCH v10 13/15] firmware: qcom: scm: clarify the comment in qcom_scm_pas_init_image()

On Fri, Jun 21, 2024 at 12:54 AM Elliot Berman <quic_eberman@...cinc.com> wrote:
>
> On Mon, May 27, 2024 at 02:55:03PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > The "memory protection" mechanism mentioned in the comment is the SHM
> > Bridge. This is also the reason why we do not convert this call to using
> > the TZ memory allocator.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > Tested-by: Andrew Halaney <ahalaney@...hat.com> # sc8280xp-lenovo-thinkpad-x13s
> > Tested-by: Deepti Jaggi <quic_djaggi@...cinc.com> #sa8775p-ride
> > Reviewed-by: Elliot Berman <quic_eberman@...cinc.com>
> > ---
> >  drivers/firmware/qcom/qcom_scm.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
> > index c82957727650..86e26f17ca19 100644
> > --- a/drivers/firmware/qcom/qcom_scm.c
> > +++ b/drivers/firmware/qcom/qcom_scm.c
> > @@ -583,6 +583,13 @@ int qcom_scm_pas_init_image(u32 peripheral, const void *metadata, size_t size,
> >        * During the scm call memory protection will be enabled for the meta
> >        * data blob, so make sure it's physically contiguous, 4K aligned and
> >        * non-cachable to avoid XPU violations.
> > +      *
> > +      * For PIL calls the hypervisor creates SHM Bridges for the blob
> > +      * buffers on behalf of Linus so we must not do it ourselves hence
>                                 Linux

Can this be fixed when applying? I don't think there's anything else
that warrants a respin.

Bart

> > +      * not using the TZMem allocator here.
> > +      *
> > +      * If we pass a buffer that is already part of an SHM Bridge to this
> > +      * call, it will fail.
> >        */
> >       mdata_buf = dma_alloc_coherent(__scm->dev, size, &mdata_phys,
> >                                      GFP_KERNEL);
> >
> > --
> > 2.43.0
> >