From mboxrd@z Thu Jan 1 00:00:00 1970 From: shankerd@codeaurora.org (Shanker Donthineni) Date: Mon, 19 Feb 2018 09:38:07 -0600 Subject: [PATCH] KVM: arm/arm64: No need to zero CNTVOFF in kvm_timer_vcpu_put() for VHE Message-ID: <1519054687-14405-1-git-send-email-shankerd@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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. Signed-off-by: Shanker Donthineni --- virt/kvm/arm/arch_timer.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index 70268c0..86eca324 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); } /* -- Qualcomm Datacenter Technologies, Inc. on behalf of the Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.