[RFC PATCH 22/28] arm64: Don't expose stolen time for realm guests

Steven Price
2023-01-27T11:33:31Z

It doesn't make much sense and with the ABI as it is it's a footgun for
the VMM which makes fatal granule protection faults easy to trigger.

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 46c152a9a150..645df5968e1e 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -302,7 +302,10 @@ 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 && kvm_is_realm(kvm))
+ r = 0;
+ else
+ r = kvm_arm_pvtime_supported();
break;
case KVM_CAP_ARM_EL1_32BIT:
r = cpus_have_const_cap(ARM64_HAS_32BIT_EL1);
--
2.34.1