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Message-ID: <98f20683-bb1d-47c2-18ca-f3de61c9a91f@linaro.org>
Date: Thu, 9 Mar 2023 10:45:49 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Maximilian Luz <luzmaximilian@...il.com>,
Bjorn Andersson <andersson@...nel.org>
Cc: Andy Gross <agross@...nel.org>,
Konrad Dybcio <konrad.dybcio@...aro.org>,
Ard Biesheuvel <ardb@...nel.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Johan Hovold <johan@...nel.org>,
Sudeep Holla <sudeep.holla@....com>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
Sumit Garg <sumit.garg@...aro.org>,
Steev Klimaszewski <steev@...i.org>,
linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] firmware: Add support for Qualcomm Secure
Execution Environment SCM interface
On 08/03/2023 15:59, Maximilian Luz wrote:
> On 3/7/23 16:32, Dmitry Baryshkov wrote:
>> On 05/03/2023 04:21, Maximilian Luz wrote:
>
> [...]
>
>>> +/* -- DMA helpers.
>>> ---------------------------------------------------------- */
>>> +
>>> +/* DMA requirements for QSEECOM SCM calls. */
>>> +#define QSEECOM_DMA_ALIGNMENT 8
>>> +#define QSEECOM_DMA_ALIGN(ptr) ALIGN(ptr, QSEECOM_DMA_ALIGNMENT)
>>> +
>>> +/**
>>> + * struct qseecom_dma - DMA memory region.
>>> + * @size: Size of the memory region, in bytes.
>>> + * @virt: Pointer / virtual address to the memory, accessible by the
>>> kernel.
>>> + * @phys: Physical address of the memory region.
>>> + */
>>> +struct qseecom_dma {
>>> + unsigned long size;
>>
>> size_t ?
>
> Will fix.
>
>>> + void *virt;
>>> + dma_addr_t phys;
>>> +};
>>
>> Do we really need this wrapper and the wrappers bellow? They look like
>> a pure syntax sugar for me, hiding the dma functions from the user.
>
> The idea was that they take care of proper allocation. The Windows
> driver that
> I've reverse-engineered this from allocates memory in multiples of
> PAGE_SIZE,
> so I believe that this might be a requirement (at least on some
> systems). These
> functions are there to ensure that and with that prevent potential bugs by
> taking that responsibility from the caller.
I see. As I wrote in another comment, it might be better to review the
whole memory allocation system: pass required sizes, get the data filled.
>
>>> +
>>> +/**
>>> + * qseecom_dma_alloc() - Allocate a DMA-able memory region suitable
>>> for QSEECOM
>>> + * SCM calls.
>>> + * @dev: The device used for DMA memory allocation.
>>> + * @dma: Where to write the allocated memory addresses and size to.
>>> + * @size: Minimum size of the memory to be allocated.
>>> + * @gfp: Flags used for allocation.
>>> + *
>>> + * Allocate a DMA-able memory region suitable for interaction with SEE
>>> + * services/applications and the TzOS. The provided size is treated
>>> as the
>>> + * minimum required size and rounded up, if necessary. The actually
>>> allocated
>>> + * memory region will be stored in @dma. Allocated memory must be
>>> freed via
>>> + * qseecom_dma_free().
>>> + *
>>> + * Return: Returns zero on success, -ENOMEM on allocation failure.
>>> + */
>>> +static inline int qseecom_dma_alloc(struct device *dev, struct
>>> qseecom_dma *dma,
>>> + unsigned long size, gfp_t gfp)
>>
>> size_t size
>>
>> gfp is not used
>
> Right, that should have been passed to dma_alloc_coherent(). Will fix that.
>
>>> +{
>>> + size = PAGE_ALIGN(size);
>>> +
>>> + dma->virt = dma_alloc_coherent(dev, size, &dma->phys, GFP_KERNEL);
>>> + if (!dma->virt)
>>> + return -ENOMEM;
>>> +
>>> + dma->size = size;
>>> + return 0;
>>> +}
>>> +
>>> +/**
>>> + * qseecom_dma_free() - Free a DMA memory region.
>>> + * @dev: The device used for allocation.
>>> + * @dma: The DMA region to be freed.
>>> + *
>>> + * Free a DMA region previously allocated via qseecom_dma_alloc().
>>> Note that
>>> + * freeing sub-regions is not supported.
>>> + */
>>> +static inline void qseecom_dma_free(struct device *dev, struct
>>> qseecom_dma *dma)
>>> +{
>>> + dma_free_coherent(dev, dma->size, dma->virt, dma->phys);
>>> +}
>>> +
>>> +/**
>>> + * qseecom_dma_realloc() - Re-allocate DMA memory region with the
>>> requested size.
>>> + * @dev: The device used for allocation.
>>> + * @dma: The region descriptor to be updated.
>>> + * @size: The new requested size.
>>> + * @gfp: Flags used for allocation.
>>> + *
>>> + * Re-allocates a DMA memory region suitable for QSEECOM SCM calls
>>> to fit the
>>> + * requested amount of bytes, if necessary. Does nothing if the
>>> provided region
>>> + * already has enough space to store the requested data.
>>> + *
>>> + * See qseecom_dma_alloc() for details.
>>> + *
>>> + * Return: Returns zero on success, -ENOMEM on allocation failure.
>>> + */
>>> +static inline int qseecom_dma_realloc(struct device *dev, struct
>>> qseecom_dma *dma,
>>> + unsigned long size, gfp_t gfp)
>>> +{
>>> + if (PAGE_ALIGN(size) <= dma->size)
>>> + return 0;
>>> +
>>> + qseecom_dma_free(dev, dma);
>>> + return qseecom_dma_alloc(dev, dma, size, gfp);
>>> +}
>>
>> I'll comment on this function when commenting patch 4.
>>
>>> +
>>> +/**
>>> + * qseecom_dma_aligned() - Create a aligned DMA memory sub-region
>>> suitable for
>>> + * QSEECOM SCM calls.
>>> + * @base: Base DMA memory region, in which the new region will
>>> reside.
>>> + * @out: Descriptor to store the aligned sub-region in.
>>> + * @offset: The offset inside base region at which to place the new
>>> sub-region.
>>> + *
>>> + * Creates an aligned DMA memory region suitable for QSEECOM SCM
>>> calls at or
>>> + * after the given offset. The size of the sub-region will be set to
>>> the
>>> + * remaining size in the base region after alignment, i.e., the end
>>> of the
>>> + * sub-region will be equal the end of the base region.
>>> + *
>>> + * Return: Returns zero on success or -EINVAL if the new aligned
>>> memory address
>>> + * would point outside the base region.
>>> + */
>>> +static inline int qseecom_dma_aligned(const struct qseecom_dma
>>> *base, struct qseecom_dma *out,
>>> + unsigned long offset)
>>> +{
>>> + void *aligned = (void *)QSEECOM_DMA_ALIGN((uintptr_t)base->virt
>>> + offset);
>>> +
>>> + if (aligned - base->virt > base->size)
>>> + return -EINVAL;
>>> +
>>> + out->virt = aligned;
>>> + out->phys = base->phys + (out->virt - base->virt);
>>> + out->size = base->size - (out->virt - base->virt);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +
>>> +/* -- Common interface.
>>> ----------------------------------------------------- */
>>> +
>>> +struct qseecom_device {
>>> + struct device *dev;
>>> + struct mutex scm_call_lock; /* Guards QSEECOM SCM calls. */
>>
>> There can be only one instance of the qseecom call infrastructure.
>> Make this mutex static in the qcom_scm.c
>
> Right, will do that.
>
>>> +};
>>> +
>>> +
>>> +/* -- Secure-OS SCM call interface.
>>> ----------------------------------------- */
>>> +
>>> +#define QSEECOM_TZ_OWNER_TZ_APPS 48
>>> +#define QSEECOM_TZ_OWNER_QSEE_OS 50
>>> +
>>> +#define QSEECOM_TZ_SVC_APP_ID_PLACEHOLDER 0
>>> +#define QSEECOM_TZ_SVC_APP_MGR 1
>>> +
>>> +enum qseecom_scm_result {
>>> + QSEECOM_RESULT_SUCCESS = 0,
>>> + QSEECOM_RESULT_INCOMPLETE = 1,
>>> + QSEECOM_RESULT_BLOCKED_ON_LISTENER = 2,
>>> + QSEECOM_RESULT_FAILURE = 0xFFFFFFFF,
>>> +};
>>> +
>>> +enum qseecom_scm_resp_type {
>>> + QSEECOM_SCM_RES_APP_ID = 0xEE01,
>>> + QSEECOM_SCM_RES_QSEOS_LISTENER_ID = 0xEE02,
>>> +};
>>> +
>>> +/**
>>> + * struct qseecom_scm_resp - QSEECOM SCM call response.
>>> + * @status: Status of the SCM call. See &enum qseecom_scm_result.
>>> + * @resp_type: Type of the response. See &enum qseecom_scm_resp_type.
>>> + * @data: Response data. The type of this data is given in
>>> @resp_type.
>>> + */
>>> +struct qseecom_scm_resp {
>>> + u64 status;
>>> + u64 resp_type;
>>> + u64 data;
>>> +};
>>> +
>>> +int qseecom_scm_call(struct qseecom_device *qsee, const struct
>>> qcom_scm_desc *desc,
>>> + struct qseecom_scm_resp *res);
>>> +
>>> +
>>> +/* -- Secure App interface.
>>> ------------------------------------------------- */
>>> +
>>> +#define QSEECOM_MAX_APP_NAME_SIZE 64
>>> +
>>> +int qseecom_app_get_id(struct qseecom_device *qsee, const char
>>> *app_name, u32 *app_id);
>>> +int qseecom_app_send(struct qseecom_device *qsee, u32 app_id, struct
>>> qseecom_dma *req,
>>> + struct qseecom_dma *rsp);
>>
>> I think that only these calls should be made public / available to
>> other modules. qseecom_scm_call also is an internal helper.
>
> So move all calls to qcom_scm and only make these two public? Or move only
> qseecom_scm_call() to qcom_scm (which would require to make it public
> there,
> however). Or how would you want this to look?
I think we can make it with just these calls being public. Or even with
just the second one being public and available to other drivers. If the
app_id is a part of qseecom_app_device, we can pass that device to the
qseecom_app_send(). And qseecom_app_get_id() becomes a part of app
registration.
>
>>> +
>>> +#endif /* _LINUX_QCOM_QSEECOM_H */
>>
>
> Regards,
> Max
--
With best wishes
Dmitry
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