Re: [PATCH v3 2/5] arm64: Work around Falkor erratum 1003

Christopher Covington
2017-01-24T14:54:53Z

Hi Catalin,

On 01/11/2017 01:06 PM, Catalin Marinas wrote:
> Some minor comments below, nothing fundamental (as long as you say the
> new sequence doesn't have the speculative TLB load problem I mentioned
> on a previous version).

This workaround is documented as providing functional correctness for
both explicit and speculative memory accesses.

>> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
>> index 32682be..9ee46df 100644
>> --- a/arch/arm64/mm/proc.S
>> +++ b/arch/arm64/mm/proc.S
>> @@ -23,6 +23,7 @@
>> #include <asm/assembler.h>
>> #include <asm/asm-offsets.h>
>> #include <asm/hwcap.h>
>> +#include <asm/mmu_context.h>
>> #include <asm/pgtable.h>
>> #include <asm/pgtable-hwdef.h>
>> #include <asm/cpufeature.h>
>> @@ -140,6 +141,18 @@ ENDPROC(cpu_do_resume)
>> ENTRY(cpu_do_switch_mm)
>> mmid x1, x1 // get mm->context.id
>> bfi x0, x1, #48, #16 // set the ASID
>> +#ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003
>> +alternative_if ARM64_WORKAROUND_QCOM_FALKOR_E1003
>> + mrs x2, ttbr0_el1
>> + mov x3, #FALKOR_RESERVED_ASID
>> + bfi x2, x3, #48, #16 // reserved ASID + old BADDR
>> + msr ttbr0_el1, x2
>> + isb
>> + bfi x2, x0, #0, #48 // reserved ASID + new BADDR
>> + msr ttbr0_el1, x2
>> + isb
>> +alternative_else_nop_endif
>> +#endif
>> msr ttbr0_el1, x0 // set TTBR0
>> isb
>> post_ttbr0_update_workaround
>
> Please move the above hunk to a pre_ttbr0_update_workaround macro for
> consistency with post_ttbr0_update_workaround.

How should I deal with inputs to the macro?

A) Use no input parameters and hard code x0 usage
B) Use a macro input parameter for the new TTBR value (x0)
C) Something else

Thanks,
Cov

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