Re: [PATCH v2 03/10] arm: Modify type of actlr to register_t

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi Julien,

On 27.04.2021 11:47, Julien Grall wrote:
> Hi Michal,
> 
> On 27/04/2021 10:35, Michal Orzel wrote:
>> AArch64 registers are 64bit whereas AArch32 registers
>> are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
>> we should get rid of helpers READ/WRITE_SYSREG32
>> in favour of using READ/WRITE_SYSREG.
>> We should also use register_t type when reading sysregs
>> which can correspond to uint64_t or uint32_t.
>> Even though many AArch64 registers have upper 32bit reserved
>> it does not mean that they can't be widen in the future.
> 
> This is a pretty generic message but doesn't really explain the change itself 
> and point out this is a bug (possibly latent on current HW) because it is 
> implementation defined. IOW a CPU implementer may already have decided to use 
> the top 32-bit without our knowledge.
> 
> Cheers,
> Is the following ok?
"
AArch64 registers are 64bit whereas AArch32 registers
are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
we should get rid of helpers READ/WRITE_SYSREG32
in favour of using READ/WRITE_SYSREG.
We should also use register_t type when reading sysregs
which can correspond to uint64_t or uint32_t.
Even though many AArch64 registers have upper 32bit reserved
it does not mean that they can't be widen in the future.

ACTLR_EL1 system register bits are implementation defined
which means it is possibly a bug on current HW as the CPU
implementer may already have decided to use the top 32bit.
"

Cheers
Michal