Re: [PATCH 1/2] xen/arm: Add imx8q{m,x} platform glue

[John Ernberg <john.ernberg@xxxxxxxx>]

Hi Peng,

On 2/1/24 05:10, Peng Fan wrote:
>> Cc: Jonas Blixt <jonas.blixt@xxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
>> Subject: Re: [PATCH 1/2] xen/arm: Add imx8q{m,x} platform glue
>>
>> Hi Julien,
>>
>> On 1/31/24 13:22, Julien Grall wrote:
>>> Hi,
>>>
>>> On 31/01/2024 11:50, John Ernberg wrote:
>>>> When using Linux for dom0 there are a bunch of drivers that need to
>>>> do SMC SIP calls into the PSCI provider to enable certain hardware
>>>> bits like the watchdog.
>>>
>>> Do you know which protocol this is under the hood. Is this SCMI?
>>
>> I think I confused myself here when I wrote the commit log.
>>
>> The EL3 code in our case is ATF, and it does not appear to be SCMI, nor PSCI.
>> The register usage of these SMC SIP calls are as follows:
>> a0 - service
>> a1 - function
>> a2-a7 - args
>>
>> In ATF the handler is declared as a runtime service.
>>
>> Would the appropriate commmit message here be something along the lines
>> of below?
>> """
>> When using Linux for dom0 there are a bunch of drivers that need to do
>> SMC
>> SIP calls into the firmware to enable certain hardware bits like the 
>> watchdog.
>> """
>>>
>>>>
>>>> Provide a basic platform glue that implements the needed SMC forwarding.
>>>>
>>>> Signed-off-by: John Ernberg <john.ernberg@xxxxxxxx>
>>>> ---
>>>> NOTE: This is based on code found in NXP Xen tree located here:
>>>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit
>>>> hub.com%2Fnxp-imx%2Fimx-xen%2Fblob%2Flf-
>> 5.10.y_4.13%2Fxen%2Farch%2Far
>>>>
>> m%2Fplatforms%2Fimx8qm.c&data=05%7C02%7Cpeng.fan%40nxp.com%7C
>> 573b599a
>>>>
>> 4b4143ceca1d08dc2271e5be%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C
>> 0%7C0%7
>>>>
>> C638423119777601548%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjA
>> wMDAiLCJQI
>>>>
>> joiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=ZO
>> 0TXjL6
>>>> g0W7TIZo8x8lTNBXEZW%2BDNcLPndWlEf5D2A%3D&reserved=0
>>>
>>> Anything after --- will be removed while applied to the three. I think
>>> this NOTE should be written down in the commit message.
>>
>> Ack.
>>>
>>> You also possibly want a signed-off-by from Peng as this is his code.
>>
>> @Peng: May I add a sign-off from you?
> 
> Yeah. You could add my sign off.

Great, thanks!
> 
>>>
>>>>
>>>>    xen/arch/arm/platforms/Makefile |  1 +
>>>>    xen/arch/arm/platforms/imx8qm.c | 65
>>>> +++++++++++++++++++++++++++++++++
>>>>    2 files changed, 66 insertions(+)
>>>>    create mode 100644 xen/arch/arm/platforms/imx8qm.c
>>>>
>>>> diff --git a/xen/arch/arm/platforms/Makefile
>>>> b/xen/arch/arm/platforms/Makefile index 8632f4115f..bec6e55d1f
>> 100644
>>>> --- a/xen/arch/arm/platforms/Makefile
>>>> +++ b/xen/arch/arm/platforms/Makefile
>>>> @@ -9,5 +9,6 @@ obj-$(CONFIG_ALL_PLAT)   += sunxi.o
>>>>    obj-$(CONFIG_ALL64_PLAT) += thunderx.o
>>>>    obj-$(CONFIG_ALL64_PLAT) += xgene-storm.o
>>>>    obj-$(CONFIG_ALL64_PLAT) += brcm-raspberry-pi.o
>>>> +obj-$(CONFIG_ALL64_PLAT) += imx8qm.o
>>>>    obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp.o
>>>>    obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp-eemi.o diff --git
>>>> a/xen/arch/arm/platforms/imx8qm.c
>> b/xen/arch/arm/platforms/imx8qm.c
>>>> new file mode 100644 index 0000000000..a9cd9c3615
>>>> --- /dev/null
>>>> +++ b/xen/arch/arm/platforms/imx8qm.c
>>>> @@ -0,0 +1,65 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>>>> +/*
>>>> + * xen/arch/arm/platforms/imx8qm.c
>>>> + *
>>>> + * i.MX 8QM setup
>>>> + *
>>>> + * Copyright (c) 2016 Freescale Inc.
>>>> + * Copyright 2018-2019 NXP
>>>> + *
>>>> + *
>>>> + * Peng Fan <peng.fan@xxxxxxx>
>>>> + */
>>>> +
>>>> +#include <asm/platform.h>
>>>> +#include <asm/smccc.h>
>>>> +
>>>> +static const char * const imx8qm_dt_compat[] __initconst = {
>>>> +    "fsl,imx8qm",
>>>> +    "fsl,imx8qxp",
>>>> +    NULL
>>>> +};
>>>> +
>>>> +static bool imx8qm_smc(struct cpu_user_regs *regs) {
>>>
>>> Your implementation below will not only forward SMC for dom0 but also
>>> for any non-trusted domains. Have you investigated that all the SIP
>>> calls are safe to be called by anyone?
>>
>> We use pure virtualized domUs, so we do not expect any calls to this SMC
>> interface from the guest. I'll limit it to dom0.
> 
> Would you mind to share what features are supported in your DomU?
> 
> Pure virtualized, you using xen pv or virtio?

Not at all. We're forwarding block and networking (and additionally 
usbip over networking for USB sharing), via the Xen PV drivers.
> 
> Thanks,
> Peng.
> 

Thanks! // John Ernberg