Subject: [kvmarm] [PATCH v4 05/13] ARM: KVM: VGIC accept vcpu and dist base addresses from user space

From: [email-masked] (Marc Zyngier)
Date: Wed, 28 Nov 2012 13:22:54 +0000

On 28/11/12 13:11, Will Deacon wrote:
> On Sat, Nov 10, 2012 at 03:44:51PM +0000, Christoffer Dall wrote:
>> User space defines the model to emulate to a guest and should therefore
>> decide which addresses are used for both the virtual CPU interface
>> directly mapped in the guest physical address space and for the emulated
>> distributor interface, which is mapped in software by the in-kernel VGIC
>> support.
>>
>> Signed-off-by: Christoffer Dall <[email-masked]>
>> ---
>>  arch/arm/include/asm/kvm_mmu.h  |    2 +
>>  arch/arm/include/asm/kvm_vgic.h |    9 ++++++
>>  arch/arm/kvm/arm.c              |   16 ++++++++++
>>  arch/arm/kvm/vgic.c             |   61 +++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 87 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
>> index 9bd0508..0800531 100644
>> --- a/arch/arm/include/asm/kvm_mmu.h
>> +++ b/arch/arm/include/asm/kvm_mmu.h
>> @@ -26,6 +26,8 @@
>>   * To save a bit of memory and to avoid alignment issues we assume 39-bit IPA
>>   * for now, but remember that the level-1 table must be aligned to its size.
>>   */
>> +#define KVM_PHYS_SHIFT	(38)
> 
> Seems a bit small...

It's now been fixed to be 40 bits.

> +#define KVM_PHYS_MASK	((1ULL << KVM_PHYS_SHIFT) - 1)
>>  #define PTRS_PER_PGD2	512
>>  #define PGD2_ORDER	get_order(PTRS_PER_PGD2 * sizeof(pgd_t))
>>  
>> diff --git a/arch/arm/include/asm/kvm_vgic.h b/arch/arm/include/asm/kvm_vgic.h
>> index b444ecf..9ca8d21 100644
>> --- a/arch/arm/include/asm/kvm_vgic.h
>> +++ b/arch/arm/include/asm/kvm_vgic.h
>> @@ -20,6 +20,9 @@
>>  #define __ASM_ARM_KVM_VGIC_H
>>  
>>  struct vgic_dist {
>> +	/* Distributor and vcpu interface mapping in the guest */
>> +	phys_addr_t		vgic_dist_base;
>> +	phys_addr_t		vgic_cpu_base;
>>  };
>>  
>>  struct vgic_cpu {
>> @@ -31,6 +34,7 @@ struct kvm_run;
>>  struct kvm_exit_mmio;
>>  
>>  #ifdef CONFIG_KVM_ARM_VGIC
>> +int kvm_vgic_set_addr(struct kvm *kvm, unsigned long type, u64 addr);
>>  bool vgic_handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
>>  		      struct kvm_exit_mmio *mmio);
>>  
>> @@ -40,6 +44,11 @@ static inline int kvm_vgic_hyp_init(void)
>>  	return 0;
>>  }
>>  
>> +static inline int kvm_vgic_set_addr(struct kvm *kvm, unsigned long type, u64 addr)
>> +{
>> +	return 0;
>> +}
>> +
>>  static inline int kvm_vgic_init(struct kvm *kvm)
>>  {
>>  	return 0;
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index 426828a..3ac1aab 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -61,6 +61,8 @@ static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
>>  static u8 kvm_next_vmid;
>>  static DEFINE_SPINLOCK(kvm_vmid_lock);
>>  
>> +static bool vgic_present;
>> +
>>  static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
>>  {
>>  	BUG_ON(preemptible());
>> @@ -825,7 +827,19 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
>>  static int kvm_vm_ioctl_set_device_address(struct kvm *kvm,
>>  					   struct kvm_device_address *dev_addr)
>>  {
>> -	return -ENODEV;
>> +	unsigned long dev_id, type;
>> +
>> +	dev_id = (dev_addr->id & KVM_DEVICE_ID_MASK) >> KVM_DEVICE_ID_SHIFT;
>> +	type = (dev_addr->id & KVM_DEVICE_TYPE_MASK) >> KVM_DEVICE_TYPE_SHIFT;
>> +
>> +	switch (dev_id) {
>> +	case KVM_ARM_DEVICE_VGIC_V2:
>> +		if (!vgic_present)
>> +			return -ENXIO;
>> +		return kvm_vgic_set_addr(kvm, type, dev_addr->addr);
>> +	default:
>> +		return -ENODEV;
>> +	}
>>  }
>>  
>>  long kvm_arch_vm_ioctl(struct file *filp,
>> diff --git a/arch/arm/kvm/vgic.c b/arch/arm/kvm/vgic.c
>> index 26ada3b..f85b275 100644
>> --- a/arch/arm/kvm/vgic.c
>> +++ b/arch/arm/kvm/vgic.c
>> @@ -22,6 +22,13 @@
>>  #include <linux/io.h>
>>  #include <asm/kvm_emulate.h>
>>  
>> +#define VGIC_ADDR_UNDEF		(-1)
>> +#define IS_VGIC_ADDR_UNDEF(_x)  ((_x) == (typeof(_x))VGIC_ADDR_UNDEF)
>> +
>> +#define VGIC_DIST_SIZE		0x1000
>> +#define VGIC_CPU_SIZE		0x2000
> 
> These defines might be useful to userspace so that they don't request the
> distributor and the cpu interface to be place too close together (been there,
> done that :).

Fair enough.

>> +
>> +
>>  #define ACCESS_READ_VALUE	(1 << 0)
>>  #define ACCESS_READ_RAZ		(0 << 0)
>>  #define ACCESS_READ_MASK(x)	((x) & (1 << 0))
>> @@ -136,3 +143,57 @@ bool vgic_handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run, struct kvm_exi
>>  {
>>  	return KVM_EXIT_MMIO;
>>  }
>> +
>> +static bool vgic_ioaddr_overlap(struct kvm *kvm)
>> +{
>> +	phys_addr_t dist = kvm->arch.vgic.vgic_dist_base;
>> +	phys_addr_t cpu = kvm->arch.vgic.vgic_cpu_base;
>> +
>> +	if (IS_VGIC_ADDR_UNDEF(dist) || IS_VGIC_ADDR_UNDEF(cpu))
>> +		return false;
>> +	if ((dist <= cpu && dist + VGIC_DIST_SIZE > cpu) ||
>> +	    (cpu <= dist && cpu + VGIC_CPU_SIZE > dist))
>> +		return true;
>> +	return false;
> 
> Just return the predicate that you're testing.
> 
>> +}
>> +
>> +int kvm_vgic_set_addr(struct kvm *kvm, unsigned long type, u64 addr)
>> +{
>> +	int r = 0;
>> +	struct vgic_dist *vgic = &kvm->arch.vgic;
>> +
>> +	if (addr & ~KVM_PHYS_MASK)
>> +		return -E2BIG;
>> +
>> +	if (addr & ~PAGE_MASK)
>> +		return -EINVAL;
>> +
>> +	mutex_lock(&kvm->lock);
>> +	switch (type) {
>> +	case KVM_VGIC_V2_ADDR_TYPE_DIST:
>> +		if (!IS_VGIC_ADDR_UNDEF(vgic->vgic_dist_base))
>> +			return -EEXIST;
>> +		if (addr + VGIC_DIST_SIZE < addr)
>> +			return -EINVAL;
> 
> I think somebody else pointed out the missing mutex_unlocks on the failure
> paths.

Yes, it's been fixed in the tree already.

>> +		kvm->arch.vgic.vgic_dist_base = addr;
>> +		break;
>> +	case KVM_VGIC_V2_ADDR_TYPE_CPU:
>> +		if (!IS_VGIC_ADDR_UNDEF(vgic->vgic_cpu_base))
>> +			return -EEXIST;
>> +		if (addr + VGIC_CPU_SIZE < addr)
>> +			return -EINVAL;
>> +		kvm->arch.vgic.vgic_cpu_base = addr;
>> +		break;
>> +	default:
>> +		r = -ENODEV;
>> +	}
>> +
>> +	if (vgic_ioaddr_overlap(kvm)) {
>> +		kvm->arch.vgic.vgic_dist_base = VGIC_ADDR_UNDEF;
>> +		kvm->arch.vgic.vgic_cpu_base = VGIC_ADDR_UNDEF;
>> +		return -EINVAL;
> 
> Perhaps we could put all the address checking in one place, so that the wrapping
> round zero checks and the overlap checks can be in the same function?
> 
>> +	}
>> +
>> +	mutex_unlock(&kvm->lock);
>> +	return r;
>> +}
> 
> Will
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> 

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