Re: [PATCH v5 08/22] KVM: arm64: vgic-its: Implement vgic_mmio_uaccess_write_its_creadr

[Christoffer Dall <christoffer.dall@linaro.org>]

On Fri, Apr 14, 2017 at 12:15:20PM +0200, Eric Auger wrote:
> GITS_CREADR needs to be restored so let's implement the associated
> uaccess_write_its callback. The write only is allowed if the its
> is disabled.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> ---
> v4 -> v5:
> - keep Stalled bit
> - vgic_mmio_uaccess_write_its_creadr can now return an error
> 
> v3 -> v4:
> - REGISTER_ITS_DESC_UACCESS now introduced in this patch
> - we now check the its is disabled
> ---
>  virt/kvm/arm/vgic/vgic-its.c | 42 ++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 40 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index a9a2c12..79ed1c2 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1213,6 +1213,33 @@ static unsigned long vgic_mmio_read_its_creadr(struct kvm *kvm,
>  	return extract_bytes(its->creadr, addr & 0x7, len);
>  }
>  
> +static int vgic_mmio_uaccess_write_its_creadr(struct kvm *kvm,
> +					      struct vgic_its *its,
> +					      gpa_t addr, unsigned int len,
> +					      unsigned long val)
> +{
> +	int ret = 0;
> +	u32 reg;
> +
> +	mutex_lock(&its->cmd_lock);
> +
> +	if (its->enabled) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	reg = update_64bit_reg(its->creadr, addr & 7, len, val);

you theoretically don't need this, since you prevent 32-bit accesses to
this register, but I guess it doesn't hurt...

> +	if (ITS_CMD_OFFSET(reg) >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}

can the creadr value be unaligned to the command size?  I don't think
you check that anywhere here?

Thanks,
-Christoffer

> +
> +	its->creadr = reg;
> +out:
> +	mutex_unlock(&its->cmd_lock);
> +	return ret;
> +}
> +
>  #define BASER_INDEX(addr) (((addr) / sizeof(u64)) & 0x7)
>  static unsigned long vgic_mmio_read_its_baser(struct kvm *kvm,
>  					      struct vgic_its *its,
> @@ -1317,6 +1344,16 @@ static void vgic_mmio_write_its_ctlr(struct kvm *kvm, struct vgic_its *its,
>  	.its_write = wr,					\
>  }
>  
> +#define REGISTER_ITS_DESC_UACCESS(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,
>  			      gpa_t addr, unsigned int len, unsigned long val)
>  {
> @@ -1339,8 +1376,9 @@ static struct vgic_register_region its_registers[] = {
>  	REGISTER_ITS_DESC(GITS_CWRITER,
>  		vgic_mmio_read_its_cwriter, vgic_mmio_write_its_cwriter, 8,
>  		VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
> -	REGISTER_ITS_DESC(GITS_CREADR,
> -		vgic_mmio_read_its_creadr, its_mmio_write_wi, 8,
> +	REGISTER_ITS_DESC_UACCESS(GITS_CREADR,
> +		vgic_mmio_read_its_creadr, its_mmio_write_wi,
> +		vgic_mmio_uaccess_write_its_creadr, 8,
>  		VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
>  	REGISTER_ITS_DESC(GITS_BASER,
>  		vgic_mmio_read_its_baser, vgic_mmio_write_its_baser, 0x40,
> -- 
> 2.5.5
>