arm64: KVM: Implement timer save/restore

Implement the timer save restore as a direct translation of
the assembly code version.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/hyp/Makefile

@@ -4,3 +4,4 @@
 
 obj-$(CONFIG_KVM_ARM_HOST) += vgic-v2-sr.o
 obj-$(CONFIG_KVM_ARM_HOST) += vgic-v3-sr.o
+obj-$(CONFIG_KVM_ARM_HOST) += timer-sr.o

arch/arm64/kvm/hyp/hyp.h

@@ -35,5 +35,8 @@ void __vgic_v2_restore_state(struct kvm_vcpu *vcpu);
 void __vgic_v3_save_state(struct kvm_vcpu *vcpu);
 void __vgic_v3_restore_state(struct kvm_vcpu *vcpu);
 
+void __timer_save_state(struct kvm_vcpu *vcpu);
+void __timer_restore_state(struct kvm_vcpu *vcpu);
+
 #endif /* __ARM64_KVM_HYP_H__ */
 

arch/arm64/kvm/hyp/timer-sr.c

+/*
+ * Copyright (C) 2012-2015 - ARM Ltd
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <clocksource/arm_arch_timer.h>
+#include <linux/compiler.h>
+#include <linux/kvm_host.h>
+
+#include <asm/kvm_mmu.h>
+
+#include "hyp.h"
+
+/* vcpu is already in the HYP VA space */
+void __hyp_text __timer_save_state(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+	u64 val;
+
+	if (kvm->arch.timer.enabled) {
+		timer->cntv_ctl = read_sysreg(cntv_ctl_el0);
+		timer->cntv_cval = read_sysreg(cntv_cval_el0);
+	}
+
+	/* Disable the virtual timer */
+	write_sysreg(0, cntv_ctl_el0);
+
+	/* Allow physical timer/counter access for the host */
+	val = read_sysreg(cnthctl_el2);
+	val |= CNTHCTL_EL1PCTEN | CNTHCTL_EL1PCEN;
+	write_sysreg(val, cnthctl_el2);
+
+	/* Clear cntvoff for the host */
+	write_sysreg(0, cntvoff_el2);
+}
+
+void __hyp_text __timer_restore_state(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+	u64 val;
+
+	/*
+	 * Disallow physical timer access for the guest
+	 * Physical counter access is allowed
+	 */
+	val = read_sysreg(cnthctl_el2);
+	val &= ~CNTHCTL_EL1PCEN;
+	val |= CNTHCTL_EL1PCTEN;
+	write_sysreg(val, cnthctl_el2);
+
+	if (kvm->arch.timer.enabled) {
+		write_sysreg(kvm->arch.timer.cntvoff, cntvoff_el2);
+		write_sysreg(timer->cntv_cval, cntv_cval_el0);
+		isb();
+		write_sysreg(timer->cntv_ctl, cntv_ctl_el0);
+	}
+}

include/clocksource/arm_arch_timer.h

@@ -23,6 +23,12 @@
 #define ARCH_TIMER_CTRL_IT_MASK		(1 << 1)
 #define ARCH_TIMER_CTRL_IT_STAT		(1 << 2)
 
+#define CNTHCTL_EL1PCTEN		(1 << 0)
+#define CNTHCTL_EL1PCEN			(1 << 1)
+#define CNTHCTL_EVNTEN			(1 << 2)
+#define CNTHCTL_EVNTDIR			(1 << 3)
+#define CNTHCTL_EVNTI			(0xF << 4)
+
 enum arch_timer_reg {
 	ARCH_TIMER_REG_CTRL,
 	ARCH_TIMER_REG_TVAL,