linux-kernel - Re: [PATCH V2] firmware: qcom_scm: use the SCM

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Date:   Thu, 3 Aug 2023 14:46:00 +0530
From:   Kathiravan T <quic_kathirav@...cinc.com>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Elliot Berman <eberman@...eaurora.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <quic_eberman@...cinc.com>, <stable@...r.kernel.org>
Subject: Re: [PATCH V2] firmware: qcom_scm: use the SCM_CONVENTION based on
 ARM / ARM64


On 7/14/2023 7:28 PM, Kathiravan T wrote:
>
> On 6/20/2023 11:43 AM, Kathiravan T wrote:
>>
>> On 6/7/2023 10:23 AM, Kathiravan T wrote:
>>> During SCM probe, to identify the SCM convention, scm call is made with
>>> SMC_CONVENTION_ARM_64 followed by SMC_CONVENTION_ARM_32. Based on the
>>> result what convention to be used is decided.
>>>
>>> IPQ chipsets starting from IPQ807x, supports both 32bit and 64bit 
>>> kernel
>>> variants, however TZ firmware runs in 64bit mode. When running on 32bit
>>> kernel, scm call is made with SMC_CONVENTION_ARM_64 is causing the
>>> system crash, due to the difference in the register sets between ARM 
>>> and
>>> AARCH64, which is accessed by the TZ.
>>>
>>> To avoid this, use SMC_CONVENTION_ARM_64 only on ARM64 builds.
>>
>>
>> Gentle Reminder...
>
>
> Bjorn,
>
> Can you share your thoughts on this patch?
>
>
> Thanks, Kathiravan T.


Gentle Reminder...


>
>
>>
>>
>>>
>>> Cc: stable@...r.kernel.org
>>> Fixes: 9a434cee773a ("firmware: qcom_scm: Dynamically support SMCCC 
>>> and legacy conventions")
>>> Signed-off-by: Kathiravan T <quic_kathirav@...cinc.com>
>>> ---
>>> Changes in V2:
>>>     - Added the Fixes tag and cc'd stable mailing list
>>>
>>>   drivers/firmware/qcom_scm.c | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
>>> index fde33acd46b7..db6754db48a0 100644
>>> --- a/drivers/firmware/qcom_scm.c
>>> +++ b/drivers/firmware/qcom_scm.c
>>> @@ -171,6 +171,7 @@ static enum qcom_scm_convention 
>>> __get_convention(void)
>>>       if (likely(qcom_scm_convention != SMC_CONVENTION_UNKNOWN))
>>>           return qcom_scm_convention;
>>>   +#if IS_ENABLED(CONFIG_ARM64)
>>>       /*
>>>        * Device isn't required as there is only one argument - no 
>>> device
>>>        * needed to dma_map_single to secure world
>>> @@ -191,6 +192,7 @@ static enum qcom_scm_convention 
>>> __get_convention(void)
>>>           forced = true;
>>>           goto found;
>>>       }
>>> +#endif
>>>         probed_convention = SMC_CONVENTION_ARM_32;
>>>       ret = __scm_smc_call(NULL, &desc, probed_convention, &res, true);