Re: [PATCH v6 07/24] KVM: arm64: vgic-its: Implement vgic_its_has_attr_regs and attr_regs_access

[Auger Eric <eric.auger@redhat.com>]

Hi Marc,

On 04/05/2017 16:04, Marc Zyngier wrote:
> On 04/05/17 12:44, Eric Auger wrote:
>> This patch implements vgic_its_has_attr_regs and vgic_its_attr_regs_access
>> upon the MMIO framework. VGIC ITS KVM device KVM_DEV_ARM_VGIC_GRP_ITS_REGS
>> group becomes functional.
>>
>> At least GITS_CREADR and GITS_IIDR require to differentiate a guest write
>> action from a user access. As such let's introduce a new uaccess_its_write
>> vgic_register_region callback.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>
>> ---
>> v6 -> v6:
>> - fix GITS_PIDR/CIDR accesses
>> - remove vgic_data_mmio_bus_to_host/vgic_data_host_to_mmio_bus
>> - 64b full reg access comment rewording
>> - vgic_its_attr_regs_access declaration block rework including
>>   removal of iodev
>>
>> v4 -> v5:
>> - use GITS_TYPER instead of offset 0x8
>> - uaccess_its_write now can return an error
>>
>> v3 -> v4:
>> - remove changes to the REGISTER_ITS_DESC macro. This will be handled in
>>   subsequent patch with the introduction of a new REGISTER_ITS_DESC_UACCESS
>>   macro
>> - fix IIDR access and add a comment wrt full length access
>> - handle endianness
>> - add kvm lock and vcpus lock
>> ---
>>  virt/kvm/arm/vgic/vgic-its.c  | 70 +++++++++++++++++++++++++++++++++++++++++--
>>  virt/kvm/arm/vgic/vgic-mmio.h |  9 ++++--
>>  2 files changed, 75 insertions(+), 4 deletions(-)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>> index f687e91..222fad5 100644
>> --- a/virt/kvm/arm/vgic/vgic-its.c
>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>> @@ -1469,14 +1469,80 @@ static void vgic_its_destroy(struct kvm_device *kvm_dev)
>>  int vgic_its_has_attr_regs(struct kvm_device *dev,
>>  			   struct kvm_device_attr *attr)
>>  {
>> -	return -ENXIO;
>> +	const struct vgic_register_region *region;
>> +	gpa_t offset = attr->attr;
>> +
> 
> Shouldn't you check the alignment in the same way you do it below? It
> seems a bit odd that one succeeds while the other fails with the same input.
yes makes sense

Thanks

Eric
> 
>> +	region = vgic_find_mmio_region(its_registers,
>> +				       ARRAY_SIZE(its_registers),
>> +				       offset);
>> +	if (!region)
>> +		return -ENXIO;
>> +
>> +	return 0;
>>  }
>>  
>>  int vgic_its_attr_regs_access(struct kvm_device *dev,
>>  			      struct kvm_device_attr *attr,
>>  			      u64 *reg, bool is_write)
>>  {
>> -	return -ENXIO;
>> +	const struct vgic_register_region *region;
>> +	struct vgic_its *its;
>> +	gpa_t addr, offset;
>> +	unsigned int len;
>> +	int align, ret = 0;
>> +
>> +	its = dev->private;
>> +	offset = attr->attr;
>> +
>> +	/*
>> +	 * Although the spec supports upper/lower 32-bit accesses to
>> +	 * 64-bit ITS registers, the userspace ABI requires 64-bit
>> +	 * accesses to all 64-bit wide registers. We therefore only
>> +	 * support 32-bit accesses to GITS_CTLR, GITS_IIDR and GITS ID
>> +	 * registers
>> +	 */
>> +	align = (offset < GITS_TYPER) || (offset >= GITS_PIDR4) ? 0x3 : 0x7;
>> +
>> +	if (offset & align)
>> +		return -EINVAL;
>> +
>> +	mutex_lock(&dev->kvm->lock);
>> +
>> +	if (IS_VGIC_ADDR_UNDEF(its->vgic_its_base)) {
>> +		ret = -ENXIO;
>> +		goto out;
>> +	}
>> +
>> +	region = vgic_find_mmio_region(its_registers,
>> +				       ARRAY_SIZE(its_registers),
>> +				       offset);
>> +	if (!region) {
>> +		ret = -ENXIO;
>> +		goto out;
>> +	}
>> +
>> +	if (!lock_all_vcpus(dev->kvm)) {
>> +		ret = -EBUSY;
>> +		goto out;
>> +	}
>> +
>> +	addr = its->vgic_its_base + offset;
>> +
>> +	len = region->access_flags & VGIC_ACCESS_64bit ? 8 : 4;
>> +
>> +	if (is_write) {
>> +		if (region->uaccess_its_write)
>> +			ret = region->uaccess_its_write(dev->kvm, its, addr,
>> +							len, *reg);
>> +		else
>> +			region->its_write(dev->kvm, its, addr, len, *reg);
>> +	} else {
>> +		*reg = region->its_read(dev->kvm, its, addr, len);
>> +	}
>> +	unlock_all_vcpus(dev->kvm);
>> +out:
>> +	mutex_unlock(&dev->kvm->lock);
>> +	return ret;
>>  }
>>  
>>  static int vgic_its_has_attr(struct kvm_device *dev,
>> diff --git a/virt/kvm/arm/vgic/vgic-mmio.h b/virt/kvm/arm/vgic/vgic-mmio.h
>> index 6eec91b..ea4171a 100644
>> --- a/virt/kvm/arm/vgic/vgic-mmio.h
>> +++ b/virt/kvm/arm/vgic/vgic-mmio.h
>> @@ -36,8 +36,13 @@ struct vgic_register_region {
>>  	};
>>  	unsigned long (*uaccess_read)(struct kvm_vcpu *vcpu, gpa_t addr,
>>  				      unsigned int len);
>> -	void (*uaccess_write)(struct kvm_vcpu *vcpu, gpa_t addr,
>> -			      unsigned int len, unsigned long val);
>> +	union {
>> +		void (*uaccess_write)(struct kvm_vcpu *vcpu, gpa_t addr,
>> +				      unsigned int len, unsigned long val);
>> +		int (*uaccess_its_write)(struct kvm *kvm, struct vgic_its *its,
>> +					 gpa_t addr, unsigned int len,
>> +					 unsigned long val);
>> +	};
>>  };
>>  
>>  extern struct kvm_io_device_ops kvm_io_gic_ops;
>>
> 
> Thanks,
> 
> 	M.
>