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

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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>
This commit is contained in:
Shanker Donthineni
2018-02-19 09:38:07 -06:00
committed by Christoffer Dall
parent b9fb17395b
commit 250be9d61c
1 changed files with 4 additions and 2 deletions
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4
virt/kvm/arm/arch_timer.c
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@@ -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);
}