Re: [PATCH v3 9/9] arm64: Work around systems with mismatched cache line sizes

[Suzuki K Poulose]

On 05/09/16 11:10, Ard Biesheuvel wrote:
> On 5 September 2016 at 10:58, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> > +/*
> > + * read_ctr - read CTR_EL0. If the system has mismatched
> > + * cache line sizes, provide the system wide safe value.
> > + */
> > +       .macro  read_ctr, reg
> > +alternative_if_not ARM64_MISMATCHED_CACHE_LINE_SIZE
> > +       mrs     \reg, ctr_el0                   // read CTR
> > +       nop
> > +       nop
> > +alternative_else
> > +       adr_l   \reg, arm64_ftr_reg_ctrel0      // Read system wide safe CTR value
> > +       ldr     \reg, [\reg, #ARM64_FTR_SYSVAL] // from arm64_ftr_reg_ctrel0.sys_val
>
> You should be able to use
>
> ldr_l \reg, arm64_ftr_reg_ctrel0 + ARM64_FTR_SYSVAL
>
> here, and save one instruction.

I had given a thought about that and chose the above to account for a
rare chance of arm64_ftr_reg_ctrel0 spanning across a 4K boundary. But,
you are right, ldr_l could treat (arm64_ftr_reg_ctrel0 + ARM64_FTR_SYSVAL)
as the symbol address and still get the right offset.

Suzuki