Re: [PATCH v7 26/45] arm64: Don't expose stolen time for realm guests

[Gavin Shan]

On 2/14/25 2:14 AM, Steven Price wrote:
> It doesn't make much sense as a realm guest wouldn't want to trust the
> host. It will also need some extra work to ensure that KVM will only
> attempt to write into a shared memory region. So for now just disable
> it.
>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Signed-off-by: Steven Price <steven.price@xxxxxxx>
> ---
>   arch/arm64/kvm/arm.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)

With Documentation/virt/kvm/api.rst updated:

Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>

> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index a6718dec00c9..79d541c95bfb 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -403,7 +403,10 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>   		r = system_supports_mte();
>   		break;
>   	case KVM_CAP_STEAL_TIME:
> -		r = kvm_arm_pvtime_supported();
> +		if (kvm_is_realm(kvm))
> +			r = 0;
> +		else
> +			r = kvm_arm_pvtime_supported();
>   		break;
>   	case KVM_CAP_ARM_EL1_32BIT:
>   		r = cpus_have_final_cap(ARM64_HAS_32BIT_EL1);