Re: [PATCH v2 1/6] arm64: Provide basic EL2 setup for FEAT_{LS64, LS64_V} usage at EL0/1

[Yicong Yang <yangyicong@huawei.com>]

On 2025/4/3 17:04, Suzuki K Poulose wrote:
> On 31/03/2025 10:43, Yicong Yang wrote:
>> From: Yicong Yang <yangyicong@hisilicon.com>
>>
>> Instructions introduced by FEAT_{LS64, LS64_V} is controlled by
>> HCRX_EL2.{EnALS, EnASR}. Configure all of these to allow usage
>> at EL0/1.
>>
>> This doesn't mean these instructions are always available in
>> EL0/1 if provided. The hypervisor still have the control at
>> runtime.
>>
>> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
>> ---
>>   arch/arm64/include/asm/el2_setup.h | 12 +++++++++++-
>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
>> index ebceaae3c749..0259941602c4 100644
>> --- a/arch/arm64/include/asm/el2_setup.h
>> +++ b/arch/arm64/include/asm/el2_setup.h
>> @@ -57,9 +57,19 @@
>>           /* Enable GCS if supported */
>>       mrs_s    x1, SYS_ID_AA64PFR1_EL1
>>       ubfx    x1, x1, #ID_AA64PFR1_EL1_GCS_SHIFT, #4
>> -    cbz    x1, .Lset_hcrx_\@
>> +    cbz    x1, .Lskip_gcs_hcrx_\@
>>       orr    x0, x0, #HCRX_EL2_GCSEn
>>   +.Lskip_gcs_hcrx_\@:
> 
> minor nit: For consistency, could we rename this "set_ls64", similar to "set_hcrx" ?
> 

IIUC, set_xxx really touches the registers and skip_xxx should just check and prepare
the feature bits. so here using .Lskip_gcs_hrcx_\@ should be more proper and consistent
with other places in el2_setup.h, like __init_el2_debug/__init_el2_fgt which also use
.Lskip_xxx for skipping an unsupported feature?

Thanks.

>> +    /* Enable LS64, LS64_V if supported */
>> +    mrs_s    x1, SYS_ID_AA64ISAR1_EL1
>> +    ubfx    x1, x1, #ID_AA64ISAR1_EL1_LS64_SHIFT, #4
>> +    cbz    x1, .Lset_hcrx_\@
>> +    orr    x0, x0, #HCRX_EL2_EnALS
>> +    cmp    x1, #ID_AA64ISAR1_EL1_LS64_LS64_V
>> +    b.lt    .Lset_hcrx_\@
>> +    orr    x0, x0, #HCRX_EL2_EnASR
>> +
>>   .Lset_hcrx_\@:
>>       msr_s    SYS_HCRX_EL2, x0
>>   .Lskip_hcrx_\@:
> 
> Suzuki
> 
> .