arm64: KVM: Plug the arch timer

Add support for the in-kernel timer emulation.
Reviewed-by: NChristopher Covington <cov@codeaurora.org>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/hyp.S

@@ -390,6 +390,60 @@ __kvm_hyp_code_start:
 2:
 .endm
 
+.macro save_timer_state
+	// x0: vcpu pointer
+	ldr	x2, [x0, #VCPU_KVM]
+	kern_hyp_va x2
+	ldr	w3, [x2, #KVM_TIMER_ENABLED]
+	cbz	w3, 1f
+
+	mrs	x3, cntv_ctl_el0
+	and	x3, x3, #3
+	str	w3, [x0, #VCPU_TIMER_CNTV_CTL]
+	bic	x3, x3, #1		// Clear Enable
+	msr	cntv_ctl_el0, x3
+
+	isb
+
+	mrs	x3, cntv_cval_el0
+	str	x3, [x0, #VCPU_TIMER_CNTV_CVAL]
+
+1:
+	// Allow physical timer/counter access for the host
+	mrs	x2, cnthctl_el2
+	orr	x2, x2, #3
+	msr	cnthctl_el2, x2
+
+	// Clear cntvoff for the host
+	msr	cntvoff_el2, xzr
+.endm
+
+.macro restore_timer_state
+	// x0: vcpu pointer
+	// Disallow physical timer access for the guest
+	// Physical counter access is allowed
+	mrs	x2, cnthctl_el2
+	orr	x2, x2, #1
+	bic	x2, x2, #2
+	msr	cnthctl_el2, x2
+
+	ldr	x2, [x0, #VCPU_KVM]
+	kern_hyp_va x2
+	ldr	w3, [x2, #KVM_TIMER_ENABLED]
+	cbz	w3, 1f
+
+	ldr	x3, [x2, #KVM_TIMER_CNTVOFF]
+	msr	cntvoff_el2, x3
+	ldr	x2, [x0, #VCPU_TIMER_CNTV_CVAL]
+	msr	cntv_cval_el0, x2
+	isb
+
+	ldr	w2, [x0, #VCPU_TIMER_CNTV_CTL]
+	and	x2, x2, #3
+	msr	cntv_ctl_el0, x2
+1:
+.endm
+
 __save_sysregs:
 	save_sysregs
 	ret
@@ -433,6 +487,7 @@ ENTRY(__kvm_vcpu_run)
 	activate_vm
 
 	restore_vgic_state
+	restore_timer_state
 
 	// Guest context
 	add	x2, x0, #VCPU_CONTEXT
@@ -455,6 +510,7 @@ __kvm_vcpu_return:
 	bl __save_fpsimd
 	bl __save_sysregs
 
+	save_timer_state
 	save_vgic_state
 
 	deactivate_traps

arch/arm64/kvm/reset.c

@@ -23,6 +23,8 @@
 #include <linux/kvm_host.h>
 #include <linux/kvm.h>
 
+#include <kvm/arm_arch_timer.h>
+
 #include <asm/cputype.h>
 #include <asm/ptrace.h>
 #include <asm/kvm_arm.h>
@@ -36,6 +38,11 @@ static const struct kvm_regs default_regs_reset = {
 			PSR_F_BIT | PSR_D_BIT),
 };
 
+static const struct kvm_irq_level default_vtimer_irq = {
+	.irq	= 27,
+	.level	= 1,
+};
+
 int kvm_arch_dev_ioctl_check_extension(long ext)
 {
 	int r;
@@ -58,11 +65,13 @@ int kvm_arch_dev_ioctl_check_extension(long ext)
  */
 int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 {
+	const struct kvm_irq_level *cpu_vtimer_irq;
 	const struct kvm_regs *cpu_reset;
 
 	switch (vcpu->arch.target) {
 	default:
 		cpu_reset = &default_regs_reset;
+		cpu_vtimer_irq = &default_vtimer_irq;
 		break;
 	}
 
@@ -72,5 +81,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 	/* Reset system registers */
 	kvm_reset_sys_regs(vcpu);
 
+	/* Reset timer */
+	kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
+
 	return 0;
 }