[PATCH 07/11] KVM: arm64: nv: Exclude guest's TWED configuration when TWE isn't set

[Oliver Upton <oliver.upton@linux.dev>]

Ignore the guest hypervisor's configured TWE delay if it hasn't actually
requested WFE traps. Otherwise, OR'ing these fields into the effective
HCR when the guest sets TWE is safe as KVM doesn't use FEAT_TWED and
leaves the fields initialized to 0.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/hyp/vhe/switch.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 0998ad4a2552..9984c492305a 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -95,6 +95,13 @@ static u64 __compute_hcr(struct kvm_vcpu *vcpu)
 			/* Force NV2 in case the guest is forgetful... */
 			guest_hcr |= HCR_NV2;
 		}
+
+		/*
+		 * Exclude the guest's TWED configuration if it hasn't set TWE
+		 * to avoid potentially delaying traps for the host.
+		 */
+		if (!(guest_hcr & HCR_TWE))
+			guest_hcr &= ~(HCR_EL2_TWEDEn | HCR_EL2_TWEDEL);
 	}
 
 	BUG_ON(host_data_test_flag(VCPU_IN_HYP_CONTEXT) &&
-- 
2.39.5