On Mon, Oct 09, 2023 at 05:34:26PM +0200, Bartosz Golaszewski wrote: > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx> > > 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 TM mem allocator. s/TM/TZ/ ? > > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx> > --- > drivers/firmware/qcom/qcom_scm.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c > index 839773270a21..8a2475ced10a 100644 > --- a/drivers/firmware/qcom/qcom_scm.c > +++ b/drivers/firmware/qcom/qcom_scm.c > @@ -563,9 +563,13 @@ int qcom_scm_pas_init_image(u32 peripheral, const void *metadata, size_t size, > struct qcom_scm_res res; > > /* > - * 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. > + * During the SCM call the TrustZone will make the buffer containing > + * the program data into an SHM Bridge. This is why we exceptionally > + * must not use the TrustZone memory allocator here as - depending on > + * Kconfig - it may already use the SHM Bridge mechanism internally. > + * > + * If we pass a buffer that is already part of an SHM Bridge to this > + * call, it will fail. I can at least confirm this matches my testing results in v2, fwiw. I guess you could use the Kconfig and conditionally use the TZ mem allocator if !SHMBridge, but I don't know if its worth the if statements or not. Bummer, I can't think of a beautiful way to unify this outside of a dedicated non SHM bridge pool for this... > */ > mdata_buf = dma_alloc_coherent(__scm->dev, size, &mdata_phys, > GFP_KERNEL); > -- > 2.39.2 >
