Commit 250be9d6 authored Feb 19, 2018 by Shanker Donthineni Committed by Christoffer Dall Feb 26, 2018

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 <marc.zyngier@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

parent b9fb1739

virt/kvm/arm/arch_timer.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -541,8 +541,10 @@ 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.
		*/
		if (!has_vhe())
		set_cntvoff(0);
		}

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