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

[Gokul krishna Krishnakumar (QUIC)]

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

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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@xxxxxxxxxxx>
> ---
>  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

Attachment: v2-0001-firmware-qcom_scm-Remove-memory-alloc-call-from-q.patch
Description: v2-0001-firmware-qcom_scm-Remove-memory-alloc-call-from-q.patch

Attachment: v2-0002-soc-qcom-mdt_loader-Move-the-memory-allocation-in.patch
Description: v2-0002-soc-qcom-mdt_loader-Move-the-memory-allocation-in.patch