[PATCH v5 26/43] arm64: Don't expose stolen time for realm guests

Steven Price posted 43 patches 1 month, 3 weeks ago
[PATCH v5 26/43] arm64: Don't expose stolen time for realm guests
Posted by Steven Price 1 month, 3 weeks ago
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.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/kvm/arm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 075c1b7306ff..bde1e0f23258 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -433,7 +433,10 @@ 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);
-- 
2.34.1
Re: [PATCH v5 26/43] arm64: Don't expose stolen time for realm guests
Posted by Suzuki K Poulose 1 month, 1 week ago
On 04/10/2024 16:27, 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.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>   arch/arm64/kvm/arm.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 075c1b7306ff..bde1e0f23258 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -433,7 +433,10 @@ 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();

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>


>   		break;
>   	case KVM_CAP_ARM_EL1_32BIT:
>   		r = cpus_have_final_cap(ARM64_HAS_32BIT_EL1);