Re: [PATCH v6 10/24] KVM: arm64: vgic-its: Implement vgic_mmio_uaccess_write_its_iidr

Christoffer Dall
2017-05-04T17:14:56Z

On Thu, May 04, 2017 at 01:44:30PM +0200, Eric Auger wrote:
> The GITS_IIDR revision field is used to encode the migration ABI
> revision. So we need to restore it to check the table layout is
> readable by the destination.
>
> By writing the IIDR, userspace thus forces the ABI revision to be
> used and this must be less than or equal to the max revision KVM
> supports.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>

Reviewed-by: Christoffer Dall <cdall@linaro.org>

> ---
> v5 -> v6:
> - fix typos in the commit message
> - dont't use update_64bit_reg anymore
>
> v4 -> v5
> - rename user_revision into abi_rev and REV into MAX_ABI_REV
> - IIDR reports abi_rev set by userspace if any.
> - If value set by userspace exceeds the max supported revision, an
> error is reported.
> - add some defines
>
> v4: creation
> ---
> include/linux/irqchip/arm-gic-v3.h | 4 ++++
> virt/kvm/arm/vgic/vgic-its.c | 20 +++++++++++++++++---
> 2 files changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
> index 81ebe43..59f1abd 100644
> --- a/include/linux/irqchip/arm-gic-v3.h
> +++ b/include/linux/irqchip/arm-gic-v3.h
> @@ -242,6 +242,10 @@
> #define GITS_TYPER_PTA (1UL << 19)
> #define GITS_TYPER_HWCOLLCNT_SHIFT 24
>
> +#define GITS_IIDR_REV_SHIFT 12
> +#define GITS_IIDR_REV(r) (((r) >> GITS_IIDR_REV_SHIFT) & 0xf)
> +#define GITS_IIDR_PRODUCTID_SHIFT 24
> +
> #define GITS_CBASER_VALID (1ULL << 63)
> #define GITS_CBASER_SHAREABILITY_SHIFT (10)
> #define GITS_CBASER_INNER_CACHEABILITY_SHIFT (59)
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index c336cce..072efbd 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -411,7 +411,20 @@ static unsigned long vgic_mmio_read_its_iidr(struct kvm *kvm,
> struct vgic_its *its,
> gpa_t addr, unsigned int len)
> {
> - return (PRODUCT_ID_KVM << 24) | (IMPLEMENTER_ARM << 0);
> + return (PRODUCT_ID_KVM << GITS_IIDR_PRODUCTID_SHIFT) |
> + (its->abi_rev << GITS_IIDR_REV_SHIFT) | IMPLEMENTER_ARM;
> +}
> +
> +static int vgic_mmio_uaccess_write_its_iidr(struct kvm *kvm,
> + struct vgic_its *its,
> + gpa_t addr, unsigned int len,
> + unsigned long val)
> +{
> + u32 rev = GITS_IIDR_REV(val);
> +
> + if (rev > MAX_ABI_REV)
> + return -EINVAL;
> + return vgic_its_set_abi(its, rev);
> }
>
> static unsigned long vgic_mmio_read_its_idregs(struct kvm *kvm,
> @@ -1393,8 +1406,9 @@ static struct vgic_register_region its_registers[] = {
> REGISTER_ITS_DESC(GITS_CTLR,
> vgic_mmio_read_its_ctlr, vgic_mmio_write_its_ctlr, 4,
> VGIC_ACCESS_32bit),
> - REGISTER_ITS_DESC(GITS_IIDR,
> - vgic_mmio_read_its_iidr, its_mmio_write_wi, 4,
> + REGISTER_ITS_DESC_UACCESS(GITS_IIDR,
> + vgic_mmio_read_its_iidr, its_mmio_write_wi,
> + vgic_mmio_uaccess_write_its_iidr, 4,
> VGIC_ACCESS_32bit),
> REGISTER_ITS_DESC(GITS_TYPER,
> vgic_mmio_read_its_typer, its_mmio_write_wi, 8,
> --
> 2.5.5
>