Re: [XEN][PATCH 3/8] xen/arm: move vcpu_switch_to_aarch64_mode() in arm64

[Grygorii Strashko <grygorii_strashko@epam.com>]

On 23.07.25 12:22, Julien Grall wrote:
> Hi,
> 
> On 23/07/2025 08:58, Grygorii Strashko wrote:
>> From: Grygorii Strashko <grygorii_strashko@epam.com>
>>
>> The vcpu_switch_to_aarch64_mode() is Arm64 specific, so move it in Arm64.
>> As part of this change:
>> - introduce arm32/arm64 domain.h headers and include them in asm/domain.h
>> basing on CONFIG_ARM_xx;
>> - declare vcpu_switch_to_aarch64_mode() for arm64;
>> - add vcpu_switch_to_aarch64_mode() as empty macro for arm32.
>>
>> Signed-off-by: Grygorii Strashko <grygorii_strashko@epam.com>
>> ---
>>   xen/arch/arm/arm64/domain.c             |  5 +++++
>>   xen/arch/arm/domain.c                   |  5 -----
>>   xen/arch/arm/include/asm/arm32/domain.h | 17 +++++++++++++++++
>>   xen/arch/arm/include/asm/arm64/domain.h | 22 ++++++++++++++++++++++
>>   xen/arch/arm/include/asm/domain.h       |  3 ++-
>>   5 files changed, 46 insertions(+), 6 deletions(-)
>>   create mode 100644 xen/arch/arm/include/asm/arm32/domain.h
>>   create mode 100644 xen/arch/arm/include/asm/arm64/domain.h
>>
>> diff --git a/xen/arch/arm/arm64/domain.c b/xen/arch/arm/arm64/domain.c
>> index dd1909892995..1e78986b5a7b 100644
>> --- a/xen/arch/arm/arm64/domain.c
>> +++ b/xen/arch/arm/arm64/domain.c
>> @@ -55,6 +55,11 @@ void vcpu_regs_user_to_hyp(struct vcpu *vcpu,
>>   #undef C
>>   }
>> +void vcpu_switch_to_aarch64_mode(struct vcpu *v)
>> +{
>> +    v->arch.hcr_el2 |= HCR_RW;
>> +}
> 
> Strictly speaking arm/domain.c is GPLv2-or-later. But arm64/domain.c doesn't have a license.
  So it would default to GPLv2-only. There have been argument in the past on whether we would
  re-license code from GPLv2-or-later to GPLv2-only. But this was never concluded. So I am not entirely sure what to do with this change...
  
> Bertrand, Michal,  Stefano?
> 
>> +
>>   /*
>>    * Local variables:
>>    * mode: C
>> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
>> index bbd4a764c696..e785278cdbd7 100644
>> --- a/xen/arch/arm/domain.c
>> +++ b/xen/arch/arm/domain.c
>> @@ -605,11 +605,6 @@ void arch_vcpu_destroy(struct vcpu *v)
>>       free_xenheap_pages(v->arch.stack, STACK_ORDER);
>>   }
>> -void vcpu_switch_to_aarch64_mode(struct vcpu *v)
>> -{
>> -    v->arch.hcr_el2 |= HCR_RW;
>> -}
>> -
>>   int arch_sanitise_domain_config(struct xen_domctl_createdomain *config)
>>   {
>>       unsigned int max_vcpus;
>> diff --git a/xen/arch/arm/include/asm/arm32/domain.h b/xen/arch/arm/include/asm/arm32/domain.h
>> new file mode 100644
>> index 000000000000..4d1251e9c128
>> --- /dev/null
>> +++ b/xen/arch/arm/include/asm/arm32/domain.h
>> @@ -0,0 +1,17 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +
>> +#ifndef ARM_ARM32_DOMAIN_H
>> +#define ARM_ARM32_DOMAIN_H
>> +
>> +#define vcpu_switch_to_aarch64_mode(v)
> 
> I think you want to "consume" v. IOW (void)(v).  That said, we tend to prefer using a static inline whenever it is possible. Have you tried it?

will do static inline.

Thank you.

-- 
Best regards,
-grygorii