linux-kernel - Re: [PATCH v2 11/11] firmware: qcom: scm: enable SHM bridge

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Date:   Fri, 29 Sep 2023 21:00:19 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        kernel@...cinc.com,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 11/11] firmware: qcom: scm: enable SHM bridge

On Thu, Sep 28, 2023 at 11:21 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> Extens the SCM memory allocator with using the SHM Bridge feature if
> available on the platform. This makes the trustzone only use dedicated
> buffers for SCM calls. We map the entire SCM genpool as a bridge.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---
>  drivers/firmware/qcom/qcom_scm-mem.c | 42 ++++++++++++++++++++++++++--
>  1 file changed, 39 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/firmware/qcom/qcom_scm-mem.c b/drivers/firmware/qcom/qcom_scm-mem.c
> index eafecbe23770..12b12b15f46f 100644
> --- a/drivers/firmware/qcom/qcom_scm-mem.c
> +++ b/drivers/firmware/qcom/qcom_scm-mem.c
> @@ -16,6 +16,8 @@
>
>  #include "qcom_scm.h"
>
> +#define QCOM_SHM_BRIDGE_NUM_VM_SHIFT 9
> +
>  static size_t qcom_scm_mem_pool_size = SZ_2M;
>  module_param_named(qcom_scm_mem_pool_size, qcom_scm_mem_pool_size,
>                    ulong, 0400);
> @@ -108,8 +110,24 @@ phys_addr_t qcom_scm_mem_to_phys(void *vaddr)
>         return chunk->paddr;
>  }
>
> +static int qcom_scm_mem_shm_bridge_create(void)
> +{
> +       uint64_t pfn_and_ns_perm, ipfn_and_s_perm, size_and_flags, ns_perms;
> +
> +       ns_perms = (QCOM_SCM_PERM_WRITE | QCOM_SCM_PERM_READ);
> +       pfn_and_ns_perm = (u64)qcom_scm_mem.pbase | ns_perms;
> +       ipfn_and_s_perm = (u64)qcom_scm_mem.pbase | ns_perms;
> +       size_and_flags = qcom_scm_mem.size | (1 << QCOM_SHM_BRIDGE_NUM_VM_SHIFT);
> +
> +       return qcom_scm_create_shm_bridge(qcom_scm_mem.dev, pfn_and_ns_perm,
> +                                         ipfn_and_s_perm, size_and_flags,
> +                                         QCOM_SCM_VMID_HLOS);
> +}
> +
>  int qcom_scm_mem_enable(struct device *dev)
>  {
> +       int ret;
> +
>         INIT_RADIX_TREE(&qcom_scm_mem.chunks, GFP_ATOMIC);
>         spin_lock_init(&qcom_scm_mem.lock);
>         qcom_scm_mem.dev = dev;
> @@ -128,7 +146,25 @@ int qcom_scm_mem_enable(struct device *dev)
>
>         gen_pool_set_algo(qcom_scm_mem.pool, gen_pool_best_fit, NULL);
>
> -       return gen_pool_add_virt(qcom_scm_mem.pool,
> -                                (unsigned long)qcom_scm_mem.vbase,
> -                                qcom_scm_mem.pbase, qcom_scm_mem.size, -1);
> +       ret = gen_pool_add_virt(qcom_scm_mem.pool,
> +                               (unsigned long)qcom_scm_mem.vbase,
> +                               qcom_scm_mem.pbase, qcom_scm_mem.size, -1);
> +       if (ret)
> +               return ret;
> +
> +       ret = qcom_scm_enable_shm_bridge();
> +       if (ret) {
> +               if (ret == EOPNOTSUPP)

FYI I noticed this is wrong, I will fix it in v3.

Bart

> +                       dev_info(dev, "SHM Bridge not supported\n");
> +               else
> +                       return ret;
> +       } else {
> +               ret = qcom_scm_mem_shm_bridge_create();
> +               if (ret)
> +                       return ret;
> +
> +               dev_info(dev, "SHM Bridge enabled\n");
> +       }
> +
> +       return 0;
>  }
> --
> 2.39.2
>