Re: [PATCH v3 0/1] arm64: Add workaround for Fujitsu A64FX erratum 010001

[James Morse]

Hi!

On 01/29/2019 12:29 PM, Zhang, Lei wrote:
> On some variants of the Fujitsu-A64FX cores ver(1.0, 1.1),
> memory accesses may cause undefined fault (Data abort, DFSC=0b111111).
> This problem will be fixed by next version of Fujitsu-A64FX.
>
> This fault occurs under a specific hardware condition
> when a load/store instruction perform an address translation using:
>    case-1  TTBR0_EL1 with TCR_EL1.NFD0 == 1.
>    case-2  TTBR0_EL2 with TCR_EL2.NFD0 == 1.
>    case-3  TTBR1_EL1 with TCR_EL1.NFD1 == 1.
>    case-4  TTBR1_EL2 with TCR_EL2.NFD1 == 1.
> And this fault occurs completely spurious.
>
> Since TCR_ELx.NFD1 is set to '1' at the kernel in versions
> past 4.17, the case-3 or case-4 may happen.

e03e61c3173c ("arm64: kaslr: Set TCR_EL1.NFD1 when 
CONFIG_RANDOMIZE_BASE=y") ?

So you'd never see it if you disabled CONFIG_RANDOMIZE_BASE?


Thanks,

James