Re: [PATCH 2/9] arm/domain: Get rid of READ/WRITE_SYSREG32

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi Julien,

On 20.04.2021 15:12, Julien Grall wrote:
> Hi Michal,
> 
> On 20/04/2021 08:08, Michal Orzel wrote:
>> AArch64 system registers are 64bit whereas AArch32 ones
>> 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 sysregs have upper 32bit reserved
>> it does not mean that they can't be widen in the future.
>>
>> Modify type of registers: actlr, cntkctl to register_t.
> 
> ACTLR is implementation defined, so in theory there might already bits 
> already defined in the range [32:63]. So I would consider to split it from 
> the patch so we can backport it.
> 
You mean not to touch it at all in this series or to create a seperate patch 
only for ACTLR?
>>
>> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
>> ---
>>   xen/arch/arm/domain.c        | 20 ++++++++++----------
>>   xen/include/asm-arm/domain.h |  4 ++--
>>   2 files changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
>> index bdd3d3e5b5..c021a03c61 100644
>> --- a/xen/arch/arm/domain.c
>> +++ b/xen/arch/arm/domain.c
>> @@ -113,13 +113,13 @@ static void ctxt_switch_from(struct vcpu *p)
>>       p->arch.tpidr_el1 = READ_SYSREG(TPIDR_EL1);
>>         /* Arch timer */
>> -    p->arch.cntkctl = READ_SYSREG32(CNTKCTL_EL1);
>> +    p->arch.cntkctl = READ_SYSREG(CNTKCTL_EL1);
>>       virt_timer_save(p);
>>         if ( is_32bit_domain(p->domain) && cpu_has_thumbee )
>>       {
>> -        p->arch.teecr = READ_SYSREG32(TEECR32_EL1);
>> -        p->arch.teehbr = READ_SYSREG32(TEEHBR32_EL1);
>> +        p->arch.teecr = READ_SYSREG(TEECR32_EL1);
>> +        p->arch.teehbr = READ_SYSREG(TEEHBR32_EL1);
> 
> It feels strange you converted cntkctl and actlr to use register_t but not 
> teecr and teehbr. Can you explain why?
> 
Because thumbee and its registers do not appear in any of ARMv8 ARM version.
This means that this code could be protected even with #ifdef CONFIG_ARM_32 as 
AArch64 do not have them.
> Cheers,
> 
Cheers,
Michal