On Mon, Aug 03, 2020 at 01:31:27PM -0600, Rob Herring wrote:
> @@ -979,6 +980,14 @@
>               write_sysreg(__scs_new, sysreg);                        \
>  } while (0)
> 
> +#define read_sysreg_par() ({                                         \
> +     u64 par;                                                        \
> +     asm(ALTERNATIVE("nop", "dmb sy", ARM64_WORKAROUND_1508412));    \
> +     par = read_sysreg(par_el1);                                     \
> +     asm(ALTERNATIVE("nop", "dmb sy", ARM64_WORKAROUND_1508412));    \
> +     par;                                                            \
> +})

I was about to queue this up but one more point to clarify: can we get
an interrupt at either side of the PAR_EL1 read and the handler do a
device read, triggering the erratum? Do we need a DMB at exception
entry/return?

-- 
Catalin
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