linux-kernel - RE: [PATCH v1 2/2] soc: qcom: mdt_loader: Move the memory allocation into mdt loader

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Message-ID: <40718b43db8f4702b0dbfec79b6fc8ab@quicinc.com>
Date:   Wed, 21 Sep 2022 16:39:46 +0000
From:   "Gokul krishna Krishnakumar (QUIC)" <quic_gokukris@...cinc.com>
To:     Bjorn Andersson <andersson@...nel.org>,
        "Gokul krishna Krishnakumar (QUIC)" <quic_gokukris@...cinc.com>
CC:     Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Trilok Soni (QUIC)" <quic_tsoni@...cinc.com>,
        "Satya Durga Srinivasu Prabhala (QUIC)" <quic_satyap@...cinc.com>,
        "Rajendra Nayak (QUIC)" <quic_rjendra@...cinc.com>,
        "Elliot Berman (QUIC)" <quic_eberman@...cinc.com>,
        "Guru Das Srinagesh (QUIC)" <quic_gurus@...cinc.com>
Subject: RE: [PATCH v1 2/2] soc: qcom: mdt_loader: Move the memory allocation
 into mdt loader

>At the end of this function we invoke kfree(metadata), which would be bad if that comes from dma_alloc_coherent().
+       if (mdata_phys) {
+               data = dma_alloc_coherent(dev, ehdr_size + hash_size, mdata_phys,
+                                      GFP_KERNEL);
+       } else {
+               data = kmalloc(ehdr_size + hash_size, GFP_KERNEL);
Adding dma_alloc_coherent without affecting the mss driver.


> As LKP points out, I don't seem to have this function.
Removing the qcom_get_scm_device() and calling dma_alloc_coherent from device context.
+               data = dma_alloc_coherent(dev, ehdr_size + hash_size, mdata_phys,
+                                      GFP_KERNEL);

>I am not thrilled about the idea of doing dma_alloc_coherent() in this file and dma_free_coherent() in the scm driver. Similarly, I consider these functions to operate in the context of the caller, so operating on the scm device's struct device isn't so nice.
>After trying various models I came to the conclusion that it was better to try to keep the MDT loader to just load MDT files, and move the SCM/PAS interaction out of that. Unfortunately we have a number of client drivers that would then need to (essentially) duplicate the content of qcom_mdt_pas_init() - so I left >that in there.
>I still believe that keeping the MDT loader focused on loading MDTs is a good idea, but I'm open to any suggestions for improvements in the interaction between these different components.

With this patch we moving all the dma_alloc_coherent() and dma_free_coherent() to the MDT loader.
So now the MDT loader has the functionality of loading and allocating memory
and the SCM driver packs the arguments and makes a call to the secure world.

-----Original Message-----
From: Bjorn Andersson <andersson@...nel.org> 
Sent: Tuesday, September 13, 2022 4:11 PM
To: Gokul krishna Krishnakumar (QUIC) <quic_gokukris@...cinc.com>
Cc: Andy Gross <agross@...nel.org>; Konrad Dybcio <konrad.dybcio@...ainline.org>; Philipp Zabel <p.zabel@...gutronix.de>; linux-arm-msm@...r.kernel.org; linux-kernel@...r.kernel.org; Trilok Soni (QUIC) <quic_tsoni@...cinc.com>; Satya Durga Srinivasu Prabhala (QUIC) <quic_satyap@...cinc.com>; Rajendra Nayak (QUIC) <quic_rjendra@...cinc.com>; Elliot Berman (QUIC) <quic_eberman@...cinc.com>; Guru Das Srinagesh (QUIC) <quic_gurus@...cinc.com>
Subject: Re: [PATCH v1 2/2] soc: qcom: mdt_loader: Move the memory allocation into mdt loader

WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable macros.

On Mon, Sep 12, 2022 at 11:41:32AM -0700, Gokul krishna Krishnakumar wrote:
> By moving the memory allocation to mdt loader we can simplify the scm 
> call, by just packing arguments provided to it from the clients for 
> making secuer world calls. We can also simplify the memory allocation 
> for the qcom metadata, by just doing one memory allocation in the mdt 
> loader.
>
> Signed-off-by: Gokul krishna Krishnakumar <quic_gokukris@...cinc.com>
> ---
>  drivers/remoteproc/qcom_q6v5_mss.c  |  2 +-
>  drivers/soc/qcom/mdt_loader.c       | 41 ++++++++++++++++++++++++++++---------
>  include/linux/soc/qcom/mdt_loader.h |  5 +++--
>  3 files changed, 35 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/remoteproc/qcom_q6v5_mss.c 
> b/drivers/remoteproc/qcom_q6v5_mss.c
> index fddb63c..1919bfc 100644
> --- a/drivers/remoteproc/qcom_q6v5_mss.c
> +++ b/drivers/remoteproc/qcom_q6v5_mss.c
> @@ -947,7 +947,7 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
>       int ret;
>       int i;
>
> -     metadata = qcom_mdt_read_metadata(fw, &size, fw_name, qproc->dev);
> +     metadata = qcom_mdt_read_metadata(fw, &size, fw_name, 
> + qproc->dev, NULL);

At the end of this function we invoke kfree(metadata), which would be bad if that comes from dma_alloc_coherent().

>       if (IS_ERR(metadata))
>               return PTR_ERR(metadata);
>
> diff --git a/drivers/soc/qcom/mdt_loader.c 
> b/drivers/soc/qcom/mdt_loader.c
[..]
> @@ -160,9 +164,18 @@ void *qcom_mdt_read_metadata(const struct firmware *fw, size_t *data_len,
>       ehdr_size = phdrs[0].p_filesz;
>       hash_size = phdrs[hash_segment].p_filesz;
>
> -     data = kmalloc(ehdr_size + hash_size, GFP_KERNEL);
> -     if (!data)
> -             return ERR_PTR(-ENOMEM);
> +     /*
> +      * 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.
> +      */
> +     scm_dev = qcom_get_scm_device();

As LKP points out, I don't seem to have this function.

> +     data = dma_alloc_coherent(scm_dev, ehdr_size + hash_size, mdata_phys,
> +                                    GFP_KERNEL);

I am not thrilled about the idea of doing dma_alloc_coherent() in this file and dma_free_coherent() in the scm driver. Similarly, I consider these functions to operate in the context of the caller, so operating on the scm device's struct device isn't so nice.


After trying various models I came to the conclusion that it was better to try to keep the MDT loader to just load MDT files, and move the SCM/PAS interaction out of that. Unfortunately we have a number of client drivers that would then need to (essentially) duplicate the content of qcom_mdt_pas_init() - so I left that in there.

I still believe that keeping the MDT loader focused on loading MDTs is a good idea, but I'm open to any suggestions for improvements in the interaction between these different components.

Regards,
Bjorn

Download attachment "v2-0001-firmware-qcom_scm-Remove-memory-alloc-call-from-q.patch" of type "application/octet-stream" (4946 bytes)

Download attachment "v2-0002-soc-qcom-mdt_loader-Move-the-memory-allocation-in.patch" of type "application/octet-stream" (9147 bytes)