[PATCH v2] ARM/KVM: save and restore generic timer registers

[christoffer.dall@linaro.org (Christoffer Dall)]

On Tue, Jun 11, 2013 at 05:16:59PM +0200, 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 also the arch timer is
> optional.
> 
> 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
> 
> Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
> ---
>  arch/arm/include/asm/kvm_host.h |  5 ++++
>  arch/arm/include/uapi/asm/kvm.h | 16 ++++++++++
>  arch/arm/kvm/arch_timer.c       | 65 +++++++++++++++++++++++++++++++++++++++++
>  arch/arm/kvm/guest.c            | 26 ++++++++++++++++-
>  4 files changed, 111 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 57cb786..1096e33 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -224,4 +224,9 @@ static inline int kvm_arch_dev_ioctl_check_extension(long ext)
>  int kvm_perf_init(void);
>  int kvm_perf_teardown(void);
>  
> +int kvm_arm_num_timer_regs(void);
> +int kvm_arm_copy_timer_indices(struct kvm_vcpu *, u64 __user *);
> +int kvm_arm_timer_get_reg(struct kvm_vcpu *, const struct kvm_one_reg *);
> +int kvm_arm_timer_set_reg(struct kvm_vcpu *, const struct kvm_one_reg *);
> +
>  #endif /* __ARM_KVM_HOST_H__ */
> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
> index c1ee007..e3b0115 100644
> --- a/arch/arm/include/uapi/asm/kvm.h
> +++ b/arch/arm/include/uapi/asm/kvm.h
> @@ -118,6 +118,22 @@ struct kvm_arch_memory_slot {
>  #define KVM_REG_ARM_32_CRN_MASK		0x0000000000007800
>  #define KVM_REG_ARM_32_CRN_SHIFT	11
>  
> +#define KVM_REG_ARM_32_CP15		(KVM_REG_ARM | KVM_REG_SIZE_U32      | \
> +					(15ULL << KVM_REG_ARM_COPROC_SHIFT))
> +#define KVM_REG_ARM_64_CP15		(KVM_REG_ARM | KVM_REG_SIZE_U64      | \
> +					(15ULL << KVM_REG_ARM_COPROC_SHIFT))
> +#define KVM_REG_ARM_TIMER_CTL		(KVM_REG_ARM_32_CP15                 | \
> +					( 3ULL << KVM_REG_ARM_CRM_SHIFT)     | \
> +					(14ULL << KVM_REG_ARM_32_CRN_SHIFT)  | \
> +					( 0ULL << KVM_REG_ARM_OPC1_SHIFT)    | \
> +					( 1ULL << KVM_REG_ARM_32_OPC2_SHIFT))
> +#define KVM_REG_ARM_TIMER_CNT		(KVM_REG_ARM_64_CP15 | \
> +					(14ULL << KVM_REG_ARM_CRM_SHIFT)     | \
> +					( 1ULL << KVM_REG_ARM_OPC1_SHIFT))
> +#define KVM_REG_ARM_TIMER_CVAL		(KVM_REG_ARM_64_CP15 | \
> +					(14ULL << KVM_REG_ARM_CRM_SHIFT)     | \
> +					( 3ULL << KVM_REG_ARM_OPC1_SHIFT))
> +
>  /* 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/arch_timer.c b/arch/arm/kvm/arch_timer.c
> index c55b608..8d709eb 100644
> --- a/arch/arm/kvm/arch_timer.c
> +++ b/arch/arm/kvm/arch_timer.c
> @@ -18,6 +18,7 @@
>  
>  #include <linux/cpu.h>
>  #include <linux/of_irq.h>
> +#include <linux/uaccess.h>
>  #include <linux/kvm.h>
>  #include <linux/kvm_host.h>
>  #include <linux/interrupt.h>
> @@ -171,6 +172,70 @@ static void kvm_timer_init_interrupt(void *info)
>  	enable_percpu_irq(timer_irq.irq, 0);
>  }
>  
> +int kvm_arm_num_timer_regs(void)
> +{
> +	return 3;
> +}
> +
> +int kvm_arm_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;
> +}
> +
> +int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> +{
> +	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> +	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;
> +
> +	switch (reg->id) {
> +	case KVM_REG_ARM_TIMER_CTL:
> +		timer->cntv_ctl = val;
> +		break;
> +	case KVM_REG_ARM_TIMER_CNT:
> +		vcpu->kvm->arch.timer.cntvoff = kvm_phys_timer_read() - val;
> +		break;
> +	case KVM_REG_ARM_TIMER_CVAL:
> +		timer->cntv_cval = val;
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +int kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> +{
> +	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> +	void __user *uaddr = (void __user *)(long)reg->addr;
> +	u64 val;
> +
> +	switch (reg->id) {
> +	case KVM_REG_ARM_TIMER_CTL:
> +		val = timer->cntv_ctl;
> +		break;
> +	case KVM_REG_ARM_TIMER_CNT:
> +		val = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
> +		break;
> +	case KVM_REG_ARM_TIMER_CVAL:
> +		val = timer->cntv_cval;
> +		break;
> +	}
> +	return copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id));
> +}
>  
>  static int kvm_timer_cpu_notify(struct notifier_block *self,
>  				unsigned long action, void *cpu)
> diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
> index 152d036..a50ffb6 100644
> --- a/arch/arm/kvm/guest.c
> +++ b/arch/arm/kvm/guest.c
> @@ -121,7 +121,8 @@ 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)
> +		+ kvm_arm_num_timer_regs();
>  }
>  
>  /**
> @@ -133,6 +134,7 @@ 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))
> @@ -140,9 +142,25 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
>  		uindices++;
>  	}
>  
> +	ret = kvm_arm_copy_timer_indices(vcpu, uindices);
> +	if (ret)
> +		return ret;
> +	uindices += kvm_arm_num_timer_regs();
> +
>  	return kvm_arm_copy_coproc_indices(vcpu, uindices);
>  }
>  
> +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;
> +}
> +
>  int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  {
>  	/* We currently use nothing arch-specific in upper 32 bits */
> @@ -153,6 +171,9 @@ 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 kvm_arm_timer_get_reg(vcpu, reg);
> +
>  	return kvm_arm_coproc_get_reg(vcpu, reg);
>  }
>  
> @@ -166,6 +187,9 @@ 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 kvm_arm_timer_set_reg(vcpu, reg);
> +
>  	return kvm_arm_coproc_set_reg(vcpu, reg);
>  }
>  
> -- 

This looks good to me!

Thanks,
-Christoffer