[RFC v2 05/19] KVM: arm64: ITS: Implement vgic_its_has_attr_regs and attr_regs_access

[Andre Przywara]

On 08/02/17 11:43, Eric Auger wrote:

Salut Eric,

one minor thing below, but first a general question:
I take it that the state of the ITS (enabled/disabled) shouldn't matter
when it comes to reading/writing registers, right? Because this is
totally under guest control and userland shouldn't mess with it?

Maybe this is handled somewhere in the next patches, but how are we
supposed to write CBASER and the BASERs, for instance, if the handler
bails out early when the ITS is already enabled?

> 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 requires 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 at redhat.com>
> ---
>  virt/kvm/arm/vgic/vgic-its.c  | 74 ++++++++++++++++++++++++++++++++++++-------
>  virt/kvm/arm/vgic/vgic-mmio.h |  9 ++++--
>  2 files changed, 69 insertions(+), 14 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 43bb17e..e9c8f9f 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1287,13 +1287,14 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
>  	*regptr = reg;
>  }
>  
> -#define REGISTER_ITS_DESC(off, rd, wr, length, acc)		\
> +#define REGISTER_ITS_DESC(off, rd, wr, uwr, length, acc)		\
>  {								\
>  	.reg_offset = off,					\
>  	.len = length,						\
>  	.access_flags = acc,					\
>  	.its_read = rd,						\
>  	.its_write = wr,					\
> +	.uaccess_its_write = uwr,					\
>  }
>  
>  static void its_mmio_write_wi(struct kvm *kvm, struct vgic_its *its,
> @@ -1304,28 +1305,28 @@ static void its_mmio_write_wi(struct kvm *kvm, struct vgic_its *its,
>  
>  static struct vgic_register_region its_registers[] = {
>  	REGISTER_ITS_DESC(GITS_CTLR,
> -		vgic_mmio_read_its_ctlr, vgic_mmio_write_its_ctlr, 4,
> +		vgic_mmio_read_its_ctlr, vgic_mmio_write_its_ctlr, NULL, 4,
>  		VGIC_ACCESS_32bit),
>  	REGISTER_ITS_DESC(GITS_IIDR,
> -		vgic_mmio_read_its_iidr, its_mmio_write_wi, 4,
> +		vgic_mmio_read_its_iidr, its_mmio_write_wi, NULL, 4,
>  		VGIC_ACCESS_32bit),
>  	REGISTER_ITS_DESC(GITS_TYPER,
> -		vgic_mmio_read_its_typer, its_mmio_write_wi, 8,
> +		vgic_mmio_read_its_typer, its_mmio_write_wi, NULL, 8,
>  		VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
>  	REGISTER_ITS_DESC(GITS_CBASER,
> -		vgic_mmio_read_its_cbaser, vgic_mmio_write_its_cbaser, 8,
> +		vgic_mmio_read_its_cbaser, vgic_mmio_write_its_cbaser, NULL, 8,
>  		VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
>  	REGISTER_ITS_DESC(GITS_CWRITER,
> -		vgic_mmio_read_its_cwriter, vgic_mmio_write_its_cwriter, 8,
> -		VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
> +		vgic_mmio_read_its_cwriter, vgic_mmio_write_its_cwriter, NULL,
> +		8, VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
>  	REGISTER_ITS_DESC(GITS_CREADR,
> -		vgic_mmio_read_its_creadr, its_mmio_write_wi, 8,
> +		vgic_mmio_read_its_creadr, its_mmio_write_wi, NULL, 8,
>  		VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
>  	REGISTER_ITS_DESC(GITS_BASER,
> -		vgic_mmio_read_its_baser, vgic_mmio_write_its_baser, 0x40,
> +		vgic_mmio_read_its_baser, vgic_mmio_write_its_baser, NULL, 0x40,
>  		VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
>  	REGISTER_ITS_DESC(GITS_IDREGS_BASE,
> -		vgic_mmio_read_its_idregs, its_mmio_write_wi, 0x30,
> +		vgic_mmio_read_its_idregs, its_mmio_write_wi, NULL, 0x30,
>  		VGIC_ACCESS_32bit),
>  };
>  
> @@ -1448,14 +1449,63 @@ 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;
> +	struct vgic_io_device iodev = {
> +		.regions = its_registers,
> +		.nr_regions = ARRAY_SIZE(its_registers),
> +	};
> +	gpa_t offset;
> +
> +	offset = attr->attr;
> +
> +	region = vgic_find_mmio_region(iodev.regions,
> +				       iodev.nr_regions,
> +				       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_io_device iodev = {
> +		.regions = its_registers,
> +		.nr_regions = ARRAY_SIZE(its_registers),
> +	};
> +	struct vgic_its *its = dev->private;
> +	gpa_t addr, offset;
> +	unsigned int len;
> +
> +	if (IS_VGIC_ADDR_UNDEF(its->vgic_its_base))
> +		return -ENXIO;
> +
> +	offset = attr->attr;
> +	if (offset & 0x7)
> +		return -EINVAL;

Isn't GITS_IIDR only 32-bit aligned?
Is it expected to just avoid reading this from userland?
If yes, it deserves a comment here, I guess.

Cheers,
Andre.

> +
> +	addr = its->vgic_its_base + offset;
> +
> +	region = vgic_find_mmio_region(iodev.regions,
> +				       iodev.nr_regions,
> +				       offset);
> +	if (!region)
> +		return -ENXIO;
> +
> +	len = region->access_flags & VGIC_ACCESS_64bit ? 8 : 4;
> +
> +	if (is_write) {
> +		if (region->uaccess_its_write)
> +			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);
> +	}
> +	return 0;
>  }
>  
>  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 055ad42..ad8a585 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);
> +		void (*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;
>