[PATCH] RISC-V: KVM: Reject overlapping AIA IMSIC address fields

[Anup Patel]

On Sat, Jul 18, 2026 at 10:05 AM Pengpeng Hou <pengpeng at iscas.ac.cn> wrote:
>
> KVM lets userspace configure the IMSIC guest, HART, group-width, and
> group-shift fields independently. The individual bounds allow a layout
> such as guest_bits=7, hart_bits=6, group_bits=1, and group_shift=24.
>
> That layout places the group index bit at bit 24 while the lower
> guest+HART field also extends through bit 24. The IMSIC address helpers
> later consume these values as one address layout: aia_imsic_ppn() masks
> the lower guest+HART field and the group field, while
> aia_imsic_hart_index() combines the group and HART index. Allowing an
> overlapping configuration therefore gives one address bit two different
> meanings.
>
> Reject group-index layouts that start before the end of the guest+HART
> field before initializing the in-kernel irqchip.
>
> Fixes: 89d01306e34d ("RISC-V: KVM: Implement device interface for AIA irqchip")
> Signed-off-by: Pengpeng Hou <pengpeng at iscas.ac.cn>

LGTM.

Reviewed-by: Anup Patel <anup at brainfault.org>

Queued this patch for Linux-7.3

Thanks,
Anup


> ---
>  arch/riscv/kvm/aia_device.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/arch/riscv/kvm/aia_device.c b/arch/riscv/kvm/aia_device.c
> index be83c2d5fc308..0793d4d4cf5e3 100644
> --- a/arch/riscv/kvm/aia_device.c
> +++ b/arch/riscv/kvm/aia_device.c
> @@ -248,6 +248,12 @@ static int aia_init(struct kvm *kvm)
>         if (aia->nr_sources && aia->aplic_addr == KVM_RISCV_AIA_UNDEF_ADDR)
>                 return -EINVAL;
>
> +       /* Group index bits must not overlap guest and HART index bits. */
> +       if (aia->nr_group_bits &&
> +           aia->nr_group_shift < IMSIC_MMIO_PAGE_SHIFT +
> +                                         aia->nr_guest_bits + aia->nr_hart_bits)
> +               return -EINVAL;
> +
>         /* Initialize APLIC */
>         ret = kvm_riscv_aia_aplic_init(kvm);
>         if (ret)
> --
> 2.43.0
>