[U-Boot] ARMv8 switching CPUs into EL1
L.S.!
On a Xilinx ZynqMP-based platform with u-boot running in Aarch64 mode in EL2, after booting a Linux kernel in EL1 using CONFIG_ARMV8_SWITCH_TO_EL1, Linux throws a warning that the CPUs have started in inconsistent modes ("CPU: CPUs started in inconsistent modes"). Indeed, only the first core on which U-boot was running is switched to EL1 at this point.
Is this a bug or a not completely supported feature in U-boot or can this warning actually be safely ignored under certain circumstances?
Kind regards,
Mels
Hi Mels,
L.S.!
On a Xilinx ZynqMP-based platform with u-boot running in Aarch64 mode in EL2, after booting a Linux kernel in EL1 using CONFIG_ARMV8_SWITCH_TO_EL1, Linux throws a warning that the CPUs have started in inconsistent modes ("CPU: CPUs started in inconsistent modes"). Indeed, only the first core on which U-boot was running is switched to EL1 at this point.
Is this a bug or a not completely supported feature in U-boot or can this warning actually be safely ignored under certain circumstances?
U-boot by design starts on Core0. Other cores are not touched and are managed (started/configured) by Linux.
The other question is if you use the ARM Trusted Firmware [ATF]. If you start/load it in U-Boot (or any earlier bootloader), then it also may change / configure CPUs state.
Kind regards,
Mels _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
Best regards,
Lukasz Majewski
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Hi,
On 06. 06. 19 15:15, Mels van Broekhoven wrote:
L.S.!
On a Xilinx ZynqMP-based platform with u-boot running in Aarch64 mode in EL2, after booting a Linux kernel in EL1 using CONFIG_ARMV8_SWITCH_TO_EL1, Linux throws a warning that the CPUs have started in inconsistent modes ("CPU: CPUs started in inconsistent modes"). Indeed, only the first core on which U-boot was running is switched to EL1 at this point.
Is this a bug or a not completely supported feature in U-boot or can this warning actually be safely ignored under certain circumstances?
I have take a look at the path and what it is happening is that ATF records that cpu0 started in EL2. Then u-boot starts Linux in EL1 because of macro above. And then Linux is asking from EL1 ATF to turn on CPU but ATF has a record that CPU0 started in EL2 that's why it starts others cpus in EL2. And then Kernel reports back that it is not consistent.
Thanks, Michal
From: Michal Simek monstr@monstr.eu Date: Tue, 11 Jun 2019 14:09:29 +0200
Hi,
On 06. 06. 19 15:15, Mels van Broekhoven wrote:
L.S.!
On a Xilinx ZynqMP-based platform with u-boot running in Aarch64 mode in EL2, after booting a Linux kernel in EL1 using CONFIG_ARMV8_SWITCH_TO_EL1, Linux throws a warning that the CPUs have started in inconsistent modes ("CPU: CPUs started in inconsistent modes"). Indeed, only the first core on which U-boot was running is switched to EL1 at this point.
Is this a bug or a not completely supported feature in U-boot or can this warning actually be safely ignored under certain circumstances?
I have take a look at the path and what it is happening is that ATF records that cpu0 started in EL2. Then u-boot starts Linux in EL1 because of macro above. And then Linux is asking from EL1 ATF to turn on CPU but ATF has a record that CPU0 started in EL2 that's why it starts others cpus in EL2. And then Kernel reports back that it is not consistent.
I'd say the answer in this situation is that you really shouldn't use the CONFIG_ARMV8_SWITCH_TO_EL1 in your configuration if you're using ATF. Or you should configure ATF such that it spins up the secondary CPUs into EL1. Not sure if there is an easy way to do that though.
participants (4)
-
Lukasz Majewski -
Mark Kettenis -
Mels van Broekhoven -
Michal Simek