On Mon, May 27, 2024 at 02:55:03PM +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 TZ memory allocator.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> Tested-by: Andrew Halaney <ahalaney@xxxxxxxxxx> # sc8280xp-lenovo-thinkpad-x13s
> Tested-by: Deepti Jaggi <quic_djaggi@xxxxxxxxxxx> #sa8775p-ride
> Reviewed-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
> ---
> 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
> + * 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
>
