Subject: [PATCH v5] ARM/KVM: save and restore generic timer registers

From: [email-masked] (Christoffer Dall)
Date: Fri, 13 Dec 2013 13:13:08 -0800

On Fri, Dec 13, 2013 at 09:35:49PM +0100, Andre Przywara wrote:
> On 12/13/2013 09:10 PM, Christoffer Dall wrote:
> >On Fri, Dec 13, 2013 at 02:23:26PM +0100, Andre Przywara wrote:
> >>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.
> >>
> >>Signed-off-by: Andre Przywara <[email-masked]>
> >>Signed-off-by: Christoffer Dall <[email-masked]>
> >>---
> >>Changes from v1:
> >>- move code out of coproc.c and into guest.c and arch_timer.c
> >>- present the registers with their native CP15 addresses, but without
> >>   using space in the VCPU's cp15 array
> >>- do the user space copying in the accessor functions
> >>
> >>Changes from v2:
> >>- fix compilation without CONFIG_ARCH_TIMER
> >>- fix compilation for arm64 by defining the appropriate registers there
> >>- move userspace access out of arch_timer.c into coproc.c
> >>- Christoffer: removed whitespace in function declaration
> >>
> >>Changes from v3:
> >>- adapted Marc's SYSREG macro magic from kvmtool for nicer looking code
> >>
> >>Changes from v4:
> >>- remove ARM64-REG32 type, the ARM ARM defines no 32-bit system registers
> >>
> >>  arch/arm/include/asm/kvm_host.h   |  3 ++
> >>  arch/arm/include/uapi/asm/kvm.h   | 20 +++++++++
> >>  arch/arm/kvm/guest.c              | 92 ++++++++++++++++++++++++++++++++++++++-
> >>  arch/arm64/include/uapi/asm/kvm.h | 18 ++++++++
> >>  virt/kvm/arm/arch_timer.c         | 34 +++++++++++++++
> >>  5 files changed, 166 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> >>index 8a6f6db..098f7dd 100644
> >>--- a/arch/arm/include/asm/kvm_host.h
> >>+++ b/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__ */
> >>diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
> >>index c498b60..835b867 100644
> >>--- a/arch/arm/include/uapi/asm/kvm.h
> >>+++ b/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)
> >>diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
> >>index 20f8d97..2786eae 100644
> >>--- a/arch/arm/kvm/guest.c
> >>+++ b/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));
> >>+}
> >>+
> >
> >how does any of this code get called for arm64?
> 
> Currently not at all. Sorry if there was a misunderstanding
> regarding this. I don't have the hardware to test this, so I just
> did the 32-bit part. The 64-bit pieces were just to make it
> _compile_ on 64-bit, which is needed because of shared code in the
> arch_timer area.
> See Marc's comment here:
> https://lists.cs.columbia.edu/pipermail/kvmarm/2013-June/006133.html
> 

ok, that's fine, I didn't test save/restore on arm64 yet either.  We can
add it later.

Otherwise the patch looks good!

Acked-by: Christoffer Dall <[email-masked]>

Thanks,
-Christoffer

> >>  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);
> >>  }
> >>
> >>diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> >>index 5031f42..7c25ca8 100644
> >>--- a/arch/arm64/include/uapi/asm/kvm.h
> >>+++ b/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
> >>diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> >>index c2e1ef4..5081e80 100644
> >>--- a/virt/kvm/arm/arch_timer.c
> >>+++ b/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)
> >>--
> >>1.7.12.1
> >>
> 

-- 
Christoffer