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SubjectRe: [PATCH] [v1] arch: arm: configs: gxp_defconfig
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Hi,

> If you get unknown instruction exceptions, that is clearly a bug that has to be
> fixed somewhere. Turning the options off should not be necessary, but we have
> to figure out why these crash, and make sure we have correct runtime detection
> in place that ensures that any driver code runs only on platforms that have the
> corresponding hardware.

> Do you have any more information about how and why these crash? My first
> guess would be that there is something in your DT that describes hardware
> that is not actually there. With a correct DTB file, the two options should
> not cause any code to run that wouldn't otherwise.

I think I found part of the issue regarding the PERF_EVENTS. In ./arch/arm/kernel/hw_breakpoint.c, the function core_has_os_save_restore is calling the mrc p14 instruction to determine ARM_OSLSR_OSLM0 value. Unfortunately per the ARM Cortex A9 documentation that call is not implemented on such core
( https://developer.arm.com/documentation/ddi0388/i/debug/debug-register-summary )

which is leading to an unknown instruction on our ASIC.

Need to figuring out how to workaround that. I will check what ARM_DEBUG_ARCH_V7_ECP14 is supposed to support. We might have either a bug into the way we report the ASIC id or something is weird into the kernel which is assuming that Cortex A9 support this PMU access.

vejmarie

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