[PATCH v3 62/66] KVM: arm64: nv: Sync nested timer state with ARMv8.4

Marc Zyngier
2020-12-10T16:23:09Z

From: Christoffer Dall <christoffer.dall@arm.com>

Emulating the ARMv8.4-NV timers is a bit odd, as the timers can
be reconfigured behind our back without the hypervisor even
noticing. In the VHE case, that's an actual regression in the
architecture...

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/arch_timer.c | 37 ++++++++++++++++++++++++++++++++++++
arch/arm64/kvm/arm.c | 3 +++
include/kvm/arm_arch_timer.h | 1 +
3 files changed, 41 insertions(+)

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 1c2be6391951..5af09d9adfe0 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -778,6 +778,43 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
set_cntvoff(0);
}

+void kvm_timer_sync_nested(struct kvm_vcpu *vcpu)
+{
+ if (!is_hyp_ctxt(vcpu))
+ return;
+
+ /*
+ * Guest hypervisors using ARMv8.4 enhanced nested virt support have
+ * their EL1 timer register accesses redirected to the VNCR page.
+ */
+ if (!vcpu_el2_e2h_is_set(vcpu)) {
+ /*
+ * For a non-VHE guest hypervisor, we update the hardware
+ * timer registers with the latest value written by the guest
+ * to the VNCR page and let the hardware take care of the
+ * rest.
+ */
+ write_sysreg_el0(__vcpu_sys_reg(vcpu, CNTV_CTL_EL0), SYS_CNTV_CTL);
+ write_sysreg_el0(__vcpu_sys_reg(vcpu, CNTV_CVAL_EL0), SYS_CNTV_CVAL);
+ write_sysreg_el0(__vcpu_sys_reg(vcpu, CNTP_CTL_EL0), SYS_CNTP_CTL);
+ write_sysreg_el0(__vcpu_sys_reg(vcpu, CNTP_CVAL_EL0), SYS_CNTP_CVAL);
+ } else {
+ /*
+ * For a VHE guest hypervisor, the emulated state (which
+ * is stored in the VNCR page) could have been updated behind
+ * our back, and we must reset the emulation of the timers.
+ */
+
+ struct timer_map map;
+ get_timer_map(vcpu, &map);
+
+ soft_timer_cancel(&map.emul_vtimer->hrtimer);
+ soft_timer_cancel(&map.emul_ptimer->hrtimer);
+ timer_emulate(map.emul_vtimer);
+ timer_emulate(map.emul_ptimer);
+ }
+}
+
/*
* With a userspace irqchip we have to check if the guest de-asserted the
* timer and if so, unmask the timer irq signal on the host interrupt
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 818ec91801e2..e8f009ed096b 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -849,6 +849,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
if (static_branch_unlikely(&userspace_irqchip_in_use))
kvm_timer_sync_user(vcpu);

+ if (enhanced_nested_virt_in_use(vcpu))
+ kvm_timer_sync_nested(vcpu);
+
kvm_arch_vcpu_ctxsync_fp(vcpu);

/*
diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index 063f613fbc7e..2e20916e9025 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -68,6 +68,7 @@ int kvm_timer_hyp_init(bool);
int kvm_timer_enable(struct kvm_vcpu *vcpu);
int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu);
void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu);
+void kvm_timer_sync_nested(struct kvm_vcpu *vcpu);
void kvm_timer_sync_user(struct kvm_vcpu *vcpu);
bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu);
void kvm_timer_update_run(struct kvm_vcpu *vcpu);
--
2.29.2