ARM/KVM: save and restore generic timer registers

For migration to work we need to save (and later restore) the state of
each core's virtual generic timer.
Since this is per VCPU, we can use the [gs]et_one_reg ioctl and export
the three needed registers (control, counter, compare value).
Though they live in cp15 space, we don't use the existing list, since
they need special accessor functions and the arch timer is optional.
Acked-by: Marc Zynger <marc.zyngier@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

arch/arm/include/asm/kvm_host.h

@@ -225,4 +225,7 @@ static inline int kvm_arch_dev_ioctl_check_extension(long ext)
 int kvm_perf_init(void);
 int kvm_perf_teardown(void);
 
+u64 kvm_arm_timer_get_reg(struct kvm_vcpu *, u64 regid);
+int kvm_arm_timer_set_reg(struct kvm_vcpu *, u64 regid, u64 value);
+
 #endif /* __ARM_KVM_HOST_H__ */

arch/arm/include/uapi/asm/kvm.h

@@ -119,6 +119,26 @@ struct kvm_arch_memory_slot {
 #define KVM_REG_ARM_32_CRN_MASK		0x0000000000007800
 #define KVM_REG_ARM_32_CRN_SHIFT	11
 
+#define ARM_CP15_REG_SHIFT_MASK(x,n) \
+	(((x) << KVM_REG_ARM_ ## n ## _SHIFT) & KVM_REG_ARM_ ## n ## _MASK)
+
+#define __ARM_CP15_REG(op1,crn,crm,op2) \
+	(KVM_REG_ARM | (15 << KVM_REG_ARM_COPROC_SHIFT) | \
+	ARM_CP15_REG_SHIFT_MASK(op1, OPC1) | \
+	ARM_CP15_REG_SHIFT_MASK(crn, 32_CRN) | \
+	ARM_CP15_REG_SHIFT_MASK(crm, CRM) | \
+	ARM_CP15_REG_SHIFT_MASK(op2, 32_OPC2))
+
+#define ARM_CP15_REG32(...) (__ARM_CP15_REG(__VA_ARGS__) | KVM_REG_SIZE_U32)
+
+#define __ARM_CP15_REG64(op1,crm) \
+	(__ARM_CP15_REG(op1, 0, crm, 0) | KVM_REG_SIZE_U64)
+#define ARM_CP15_REG64(...) __ARM_CP15_REG64(__VA_ARGS__)
+
+#define KVM_REG_ARM_TIMER_CTL		ARM_CP15_REG32(0, 14, 3, 1)
+#define KVM_REG_ARM_TIMER_CNT		ARM_CP15_REG64(1, 14) 
+#define KVM_REG_ARM_TIMER_CVAL		ARM_CP15_REG64(3, 14) 
+
 /* Normal registers are mapped as coprocessor 16. */
 #define KVM_REG_ARM_CORE		(0x0010 << KVM_REG_ARM_COPROC_SHIFT)
 #define KVM_REG_ARM_CORE_REG(name)	(offsetof(struct kvm_regs, name) / 4)

arch/arm/kvm/guest.c

@@ -109,6 +109,83 @@ int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 	return -EINVAL;
 }
 
+#ifndef CONFIG_KVM_ARM_TIMER
+
+#define NUM_TIMER_REGS 0
+
+static int copy_timer_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
+{
+	return 0;
+}
+
+static bool is_timer_reg(u64 index)
+{
+	return false;
+}
+
+int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
+{
+	return 0;
+}
+
+u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
+{
+	return 0;
+}
+
+#else
+
+#define NUM_TIMER_REGS 3
+
+static bool is_timer_reg(u64 index)
+{
+	switch (index) {
+	case KVM_REG_ARM_TIMER_CTL:
+	case KVM_REG_ARM_TIMER_CNT:
+	case KVM_REG_ARM_TIMER_CVAL:
+		return true;
+	}
+	return false;
+}
+
+static int copy_timer_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
+{
+	if (put_user(KVM_REG_ARM_TIMER_CTL, uindices))
+		return -EFAULT;
+	uindices++;
+	if (put_user(KVM_REG_ARM_TIMER_CNT, uindices))
+		return -EFAULT;
+	uindices++;
+	if (put_user(KVM_REG_ARM_TIMER_CVAL, uindices))
+		return -EFAULT;
+
+	return 0;
+}
+
+#endif
+
+static int set_timer_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+	void __user *uaddr = (void __user *)(long)reg->addr;
+	u64 val;
+	int ret;
+
+	ret = copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id));
+	if (ret != 0)
+		return ret;
+
+	return kvm_arm_timer_set_reg(vcpu, reg->id, val);
+}
+
+static int get_timer_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+	void __user *uaddr = (void __user *)(long)reg->addr;
+	u64 val;
+
+	val = kvm_arm_timer_get_reg(vcpu, reg->id);
+	return copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id));
+}
+
 static unsigned long num_core_regs(void)
 {
 	return sizeof(struct kvm_regs) / sizeof(u32);
@@ -121,7 +198,8 @@ static unsigned long num_core_regs(void)
  */
 unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
 {
-	return num_core_regs() + kvm_arm_num_coproc_regs(vcpu);
+	return num_core_regs() + kvm_arm_num_coproc_regs(vcpu)
+		+ NUM_TIMER_REGS;
 }
 
 /**
@@ -133,6 +211,7 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
 {
 	unsigned int i;
 	const u64 core_reg = KVM_REG_ARM | KVM_REG_SIZE_U32 | KVM_REG_ARM_CORE;
+	int ret;
 
 	for (i = 0; i < sizeof(struct kvm_regs)/sizeof(u32); i++) {
 		if (put_user(core_reg | i, uindices))
@@ -140,6 +219,11 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
 		uindices++;
 	}
 
+	ret = copy_timer_indices(vcpu, uindices);
+	if (ret)
+		return ret;
+	uindices += NUM_TIMER_REGS;
+
 	return kvm_arm_copy_coproc_indices(vcpu, uindices);
 }
 
@@ -153,6 +237,9 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
 		return get_core_reg(vcpu, reg);
 
+	if (is_timer_reg(reg->id))
+		return get_timer_reg(vcpu, reg);
+
 	return kvm_arm_coproc_get_reg(vcpu, reg);
 }
 
@@ -166,6 +253,9 @@ int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
 		return set_core_reg(vcpu, reg);
 
+	if (is_timer_reg(reg->id))
+		return set_timer_reg(vcpu, reg);
+
 	return kvm_arm_coproc_set_reg(vcpu, reg);
 }
 

arch/arm64/include/uapi/asm/kvm.h

@@ -129,6 +129,24 @@ struct kvm_arch_memory_slot {
 #define KVM_REG_ARM64_SYSREG_OP2_MASK	0x0000000000000007
 #define KVM_REG_ARM64_SYSREG_OP2_SHIFT	0
 
+#define ARM64_SYS_REG_SHIFT_MASK(x,n) \
+	(((x) << KVM_REG_ARM64_SYSREG_ ## n ## _SHIFT) & \
+	KVM_REG_ARM64_SYSREG_ ## n ## _MASK)
+
+#define __ARM64_SYS_REG(op0,op1,crn,crm,op2) \
+	(KVM_REG_ARM64 | KVM_REG_ARM64_SYSREG | \
+	ARM64_SYS_REG_SHIFT_MASK(op0, OP0) | \
+	ARM64_SYS_REG_SHIFT_MASK(op1, OP1) | \
+	ARM64_SYS_REG_SHIFT_MASK(crn, CRN) | \
+	ARM64_SYS_REG_SHIFT_MASK(crm, CRM) | \
+	ARM64_SYS_REG_SHIFT_MASK(op2, OP2))
+
+#define ARM64_SYS_REG(...) (__ARM64_SYS_REG(__VA_ARGS__) | KVM_REG_SIZE_U64)
+
+#define KVM_REG_ARM_TIMER_CTL		ARM64_SYS_REG(3, 3, 14, 3, 1)
+#define KVM_REG_ARM_TIMER_CNT		ARM64_SYS_REG(3, 3, 14, 3, 2)
+#define KVM_REG_ARM_TIMER_CVAL		ARM64_SYS_REG(3, 3, 14, 0, 2)
+
 /* KVM_IRQ_LINE irq field index values */
 #define KVM_ARM_IRQ_TYPE_SHIFT		24
 #define KVM_ARM_IRQ_TYPE_MASK		0xff

virt/kvm/arm/arch_timer.c

@@ -182,6 +182,40 @@ static void kvm_timer_init_interrupt(void *info)
 	enable_percpu_irq(host_vtimer_irq, 0);
 }
 
+int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
+{
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+
+	switch (regid) {
+	case KVM_REG_ARM_TIMER_CTL:
+		timer->cntv_ctl = value;
+		break;
+	case KVM_REG_ARM_TIMER_CNT:
+		vcpu->kvm->arch.timer.cntvoff = kvm_phys_timer_read() - value;
+		break;
+	case KVM_REG_ARM_TIMER_CVAL:
+		timer->cntv_cval = value;
+		break;
+	default:
+		return -1;
+	}
+	return 0;
+}
+
+u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
+{
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+
+	switch (regid) {
+	case KVM_REG_ARM_TIMER_CTL:
+		return timer->cntv_ctl;
+	case KVM_REG_ARM_TIMER_CNT:
+		return kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
+	case KVM_REG_ARM_TIMER_CVAL:
+		return timer->cntv_cval;
+	}
+	return (u64)-1;
+}
 
 static int kvm_timer_cpu_notify(struct notifier_block *self,
 				unsigned long action, void *cpu)