[07/85] KVM: arm/arm64: No need to zero CNTVOFF in kvm_timer_vcpu_put() for VHE

Message ID 20180328125254.31380-8-marc.zyngier@arm.com
State New
Headers show
Series
  • [GIT,PULL] KVM/ARM updates for v4.17
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Commit Message

Marc Zyngier March 28, 2018, 12:51 p.m.
From: Shanker Donthineni <shankerd@codeaurora.org>

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>
---
 virt/kvm/arm/arch_timer.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Patch

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 70268c0bec79..86eca32474cc 100644
--- 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);
 }
 
 /*