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

From: [email-masked] (Christoffer Dall)
Date: Tue, 17 Dec 2013 11:03:18 -0800

On Tue, Dec 17, 2013 at 11:20:20AM +0000, Marc Zyngier wrote:
> On 13/12/13 20:35, 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
> 
> It would have been good if it was done at the same time, but I'm not
> even sure we have the corresponding userspace code to even test it.
> 
> So, assuming that someone will eventually implement it when QEMU/arm64
> reaches the same level as its 32bit counterpart:

We need the sysregs state in qemu to do the marshalling in a convenient
way, so I'm planning to do this once we have the skeleton for the state
in QEMU.  There is a card to track this work in Linaro.

> 
> Acked-by: Marc Zyngier <[email-masked]>
> 

Thanks, I plan on sending you a pull request with the newest versions of
these patches if you ack my latest vgic save/restore series.

-Christoffer