[v2] KVM: arm64: make EL2 feature fields writable in ID_AA64MMFR1_EL1

[PATCH v2 0/3] KVM: arm64: make EL2 feature fields writable in ID_AA64MMFR1_EL1

Posted by Jinqian Yang 3 weeks, 2 days ago

Allow userspace to downgrade EL2 features (VH, TWED, HCX) to ensure VM live
migration compatibility between hosts with varying feature support.

v1: https://lore.kernel.org/linux-arm-kernel/20250325121126.1380681-1-yangjinqian1@huawei.com/

Change Log:
v1->v2:
  -Added support for downgrading TWED and VH fields.
  -Added corresponding test cases to the set_id_regs selftest.

Jinqian Yang (3):
  KVM: arm64: Make ID_AA64MMFR1_EL1.HCX writable from userspace
  KVM: arm64: Make ID_AA64MMFR1_EL1.TWED writable from userspace
  KVM: arm64: Make ID_AA64MMFR1_EL1.VH writable from userspace

 arch/arm64/kvm/sys_regs.c                       | 3 ---
 tools/testing/selftests/kvm/arm64/set_id_regs.c | 3 +++
 2 files changed, 3 insertions(+), 3 deletions(-)

-- 
2.33.0

Re: [PATCH v2 0/3] KVM: arm64: make EL2 feature fields writable in ID_AA64MMFR1_EL1

Posted by Oliver Upton 3 weeks, 2 days ago

On Tue, Sep 09, 2025 at 11:44:12AM +0800, Jinqian Yang wrote:
> Allow userspace to downgrade EL2 features (VH, TWED, HCX) to ensure VM live
> migration compatibility between hosts with varying feature support.
> 
> v1: https://lore.kernel.org/linux-arm-kernel/20250325121126.1380681-1-yangjinqian1@huawei.com/
> 
> Change Log:
> v1->v2:
>   -Added support for downgrading TWED and VH fields.
>   -Added corresponding test cases to the set_id_regs selftest.
> 
> Jinqian Yang (3):
>   KVM: arm64: Make ID_AA64MMFR1_EL1.HCX writable from userspace
>   KVM: arm64: Make ID_AA64MMFR1_EL1.TWED writable from userspace
>   KVM: arm64: Make ID_AA64MMFR1_EL1.VH writable from userspace
> 
>  arch/arm64/kvm/sys_regs.c                       | 3 ---
>  tools/testing/selftests/kvm/arm64/set_id_regs.c | 3 +++

General comment: please make do kernel and selftest changes in separate
patches.

Thanks,
Oliver

Re: [PATCH v2 0/3] KVM: arm64: make EL2 feature fields writable in ID_AA64MMFR1_EL1

Posted by Jinqian Yang 3 weeks, 1 day ago


On 2025/9/9 15:00, Oliver Upton wrote:
> On Tue, Sep 09, 2025 at 11:44:12AM +0800, Jinqian Yang wrote:
>> Allow userspace to downgrade EL2 features (VH, TWED, HCX) to ensure VM live
>> migration compatibility between hosts with varying feature support.
>>
>> v1: https://lore.kernel.org/linux-arm-kernel/20250325121126.1380681-1-yangjinqian1@huawei.com/
>>
>> Change Log:
>> v1->v2:
>>    -Added support for downgrading TWED and VH fields.
>>    -Added corresponding test cases to the set_id_regs selftest.
>>
>> Jinqian Yang (3):
>>    KVM: arm64: Make ID_AA64MMFR1_EL1.HCX writable from userspace
>>    KVM: arm64: Make ID_AA64MMFR1_EL1.TWED writable from userspace
>>    KVM: arm64: Make ID_AA64MMFR1_EL1.VH writable from userspace
>>
>>   arch/arm64/kvm/sys_regs.c                       | 3 ---
>>   tools/testing/selftests/kvm/arm64/set_id_regs.c | 3 +++
> 
> General comment: please make do kernel and selftest changes in separate
> patches.
> 

Will be changed in v3.

Thanks,
Jinqian