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

Auger Eric
2017-05-04T15:03:21Z

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.
>