KVM: arm/arm64: No need to zero CNTVOFF in kvm_timer_vcpu_put() for VHE

In AArch64/AArch32, the virtual counter uses a fixed virtual offset of zero in the following situations as per ARMv8 specifications: 1) HCR_EL2.E2H is 1, and CNTVCT_EL0/CNTVCT are read from EL2. 2) HCR_EL2.{E2H, TGE} is {1, 1}, and either: — CNTVCT_EL0 is read from Non-secure EL0 or EL2. — CNTVCT is read from Non-secure EL0. So, no need to zero CNTVOFF_EL2/CNTVOFF for VHE case. Acked-by: Marc Zyngier <[email protected]> Acked-by: Christoffer Dall <[email protected]> Signed-off-by: Shanker Donthineni <[email protected]> Signed-off-by: Christoffer Dall <[email protected]>
akeromi · Feb 26, 2018 · 250be9d · 250be9d
1 parent b9fb173
commit 250be9d
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
@@ -541,9 +541,11 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
 	 * The kernel may decide to run userspace after calling vcpu_put, so
 	 * we reset cntvoff to 0 to ensure a consistent read between user
 	 * accesses to the virtual counter and kernel access to the physical
-	 * counter.
+	 * counter of non-VHE case. For VHE, the virtual counter uses a fixed
+	 * virtual offset of zero, so no need to zero CNTVOFF_EL2 register.
 	 */
-	set_cntvoff(0);
+	if (!has_vhe())
+		set_cntvoff(0);
 }
 
 /*