[U-Boot] [PATCH v7 1/2] armv8: Support loading 32-bit OS in AArch32 execution state

[Ryan Harkin]

On 4 November 2016 at 09:20, Alison Wang <alison.wang at nxp.com> wrote:
>> On 4 November 2016 at 02:26, Alison Wang <alison.wang at nxp.com> wrote:
>> > York,
>> >
>> >
>> >
>> >                 No, he don’t have my 32-bit kernel image. I am not
>> > sure he is using 32-bit kernel or 64-bit kernel.
>> >
>> >
>> >
>> > Ryan,
>> >
>> >
>> >
>> >                 I am not familiar with the boards you tested,
>>
>> The FVP Foundation model is free to use from ARM.  The entire software
>> stack I'm using is available via ARM's portal:
>>
>> https://community.arm.com/groups/arm-development-platforms
>>
>>
>> > so I have some
>> > questions, please help to work with me to find the root cause.
>> >
>> >
>> >
>> > 1.       Are you loading 32-bit kernel or 64-bit kernel?
>> >
>>
>> I'm loading the "standard" 64-bit kernel.  I was using a kernel based
>> off 4.8:
>>
>> https://git.linaro.org/landing-teams/working/arm/kernel-
>> release.git/log/?h=latest-armlt-20161001
>>
>> > 2.       Is CONFIG_ARMV8_SWITCH_TO_EL1 defined on these boards?
>> >
>>
>> I guess it is for the FVP models, if I grep for it, it's in my
>> configs' .h file:
>>
>> include/configs/vexpress_aemv8a.h:15:#define CONFIG_ARMV8_SWITCH_TO_EL1
>>
>> -------------------------------------------------------
>> #ifdef CONFIG_TARGET_VEXPRESS64_BASE_FVP #ifndef CONFIG_SEMIHOSTING
>> #error CONFIG_TARGET_VEXPRESS64_BASE_FVP requires CONFIG_SEMIHOSTING
>> #endif #define CONFIG_ARMV8_SWITCH_TO_EL1 #endif
>> -------------------------------------------------------
>>
>> But it isn't in my Juno config.
>>
>>
>> > 3.       Are you using some secure firmware on these boards? In
>> detail, I
>> > want to know which EL is running on these boards when calling
>> > armv8_switch_to_el2 in arch/arm/lib/bootm.c. If it is already running
>> > in EL2 when calling armv8_swith_to_el2, the attached patch with PSCI
>> > enabled is needed.
>> >
>>
>> I'm using what ARM consider the "standard" boot flow.  I'm using ARM
>> Trusted Firmware to boot u-boot which in turn boots an arm64 kernel.
>>
>> I'd expect my setup to still work after you've added patches to allow
>> an aarch32 kernel to be booted, but I guess you're changing the boot
>> path for non-aarch32 kernels also.
> [Alison Wang] Of course, although I add these patches to support aarch32
> kernel, I should make sure aarch64 kernel work too.
>
> If you are using ARM Trusted Firmware to boot u-boot, I want to know what
> EL is running for your U-Boot.

I guess I'm running U-Boot at EL2.  U-Boot is BL33 and the ARM-TF docs say:

---------------------------------------------------------
BL33 (Non-trusted Firmware) execution

EL3 Runtime Software initializes the EL2 or EL1 processor context for
normal- world cold boot, ensuring that no secure state information
finds its way into the non-secure execution state. EL3 Runtime
Software uses the entrypoint information provided by BL2 to jump to
the Non-trusted firmware image (BL33) at the highest available
Exception Level (EL2 if available, otherwise EL1).
---------------------------------------------------------


> If it is running in EL2 or EL1, please add
> the attached patch to test again.

Yes, with the attached patch on top of your original 2 patches,
everything works again.  I tested on FVP Foundation and AEMv8 models
and Juno R0, R1 and R2.

I don't think it would be good to stack these three patches the way
they are presented in the upstream tree because it would not be
bisect-able.  Some re-work or re-ordering would be needed.

Note: I haven't attempted to understand what any of this code is
doing, I'm just testing it with my standard boot flow to make sure
nothing is broken for me.


> Thanks.
>>
>> Regards,
>> Ryan.
>>
>> >
>> >
>> >
>> >
>> > Best Regards,
>> >
>> > Alison Wang
>> >
>> >
>> >
>> > From: york sun
>> > Sent: Friday, November 04, 2016 10:04 AM
>> > To: ryan.harkin at linaro.org
>> > Cc: Wang Huan <b18965 at freescale.com>; agraf at suse.de; Scott Wood
>> > <scott.wood at nxp.com>; Stuart Yoder <stuart.yoder at nxp.com>; Leo Li
>> > <leoyang.li at nxp.com>; fenghua at phytium.com.cn; monstr at monstr.eu;
>> > thomas.ab at samsung.com; mk7.kang at samsung.com; u-boot at lists.denx.de;
>> > Jason Jin <jason.jin at nxp.com>; Alison Wang <alison.wang at nxp.com>
>> >
>> >
>> > Subject: Re: [PATCH v7 1/2] armv8: Support loading 32-bit OS in
>> > AArch32 execution state
>> >
>> >
>> >
>> > Alison,
>> >
>> > Does Ryan have your 32-bit kernel image? I think kernel 32-bit
>> doesn't
>> > support spin table. Please work with Ryan if your PSCI patch is
>> > required for the test.
>> >
>> > York
>> >
>> >
>> >
>> > -------- Original Message --------
>> > From: Ryan Harkin <ryan.harkin at linaro.org>
>> > Sent: Thursday, November 3, 2016 12:17 PM
>> > To: york sun <york.sun at nxp.com>
>> > Subject: Re: [PATCH v7 1/2] armv8: Support loading 32-bit OS in
>> > AArch32 execution state
>> > CC: Alison Wang <b18965 at freescale.com>,agraf at suse.de,Scott Wood
>> > <scott.wood at nxp.com>,Stuart Yoder <stuart.yoder at nxp.com>,Leo Li
>> >
>> <leoyang.li at nxp.com>,fenghua at phytium.com.cn,monstr at monstr.eu,thomas.ab
>> > @samsung.com,mk7.kang at samsung.com,u-boot at lists.denx.de,Jason
>> > Jin <jason.jin at nxp.com>,Alison Wang <alison.wang at nxp.com>
>> >
>> > Hi York/Alison,
>> >
>> > Sorry for not having had time to look at this earlier.
>> >
>> >
>> > On 26 October 2016 at 17:54, york sun <york.sun at nxp.com> wrote:
>> >> On 10/07/2016 11:56 PM, Alison Wang wrote:
>> >>> To support loading a 32-bit OS, the execution state will change
>> from
>> >>> AArch64 to AArch32 when jumping to kernel.
>> >>>
>> >>> The architecture information will be got through checking FIT image,
>> >>> then U-Boot will load 32-bit OS or 64-bit OS automatically.
>> >>>
>> >>> Signed-off-by: Ebony Zhu <ebony.zhu at nxp.com>
>> >>> Signed-off-by: Alison Wang <alison.wang at nxp.com>
>> >>> Signed-off-by: Chenhui Zhao <chenhui.zhao at nxp.com>
>> >>> ---
>> >>> Changes in v7:
>> >>> - Move the call for armv8_switch_to_el2_m into this patch.
>> >>>
>> >>
>> >> Reviewers,
>> >>
>> >> May I have your comment please? I intend to merge this set when the
>> >> merge window opens.
>> >>
>> >
>> > I've just tested these two patches on ARM's FVP Foundation and AEMv8
>> > models and ARM's Juno board.
>> >
>> > In all cases, with this patchset, the kernel fails to start.  I see a
>> > continuous reboot, where the kernel starts then immediately resets:
>> >
>> > --------------------------------------------------
>> > Starting kernel ...
>> >
>> > resetting ...
>> > --------------------------------------------------
>> >
>> > So I wouldn't want to see these patches merged.
>> >
>> > Regards,
>> > Ryan.