Re: [PATCH v4 04/11] KVM: arm/arm64: vgic-its: Check CBASER/BASER validity before enabling the ITS

Christoffer Dall
2017-10-17T22:02:08Z

On Tue, Oct 17, 2017 at 09:10:02AM +0200, Eric Auger wrote:
> The spec says it is UNPREDICTABLE to enable the ITS
> if any of the following conditions are true:
>
> - GITS_CBASER.Valid == 0.
> - GITS_BASER<n>.Valid == 0, for any GITS_BASER<n> register
> where the Type field indicates Device.
> - GITS_BASER<n>.Valid == 0, for any GITS_BASER<n> register
> where the Type field indicates Interrupt Collection and
> GITS_TYPER.HCC == 0.
>
> In that case, let's keep the ITS disabled.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Reported-by: Andre Przywara <andre.przywara@arm.com>
>
> ---
>
> v3: creation
> ---
> virt/kvm/arm/vgic/vgic-its.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index e59363e..e61736b 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1488,6 +1488,16 @@ static void vgic_mmio_write_its_ctlr(struct kvm *kvm, struct vgic_its *its,
> its->enabled = !!(val & GITS_CTLR_ENABLE);
>
> /*
> + * It is UNPREDICTABLE to enable the ITS if any of the CBASER or
> + * device/collection BASER are invalid
> + */
> + if (its->enabled &&
> + (!(its->baser_device_table & GITS_BASER_VALID) ||
> + !(its->baser_coll_table & GITS_BASER_VALID) ||
> + !(its->cbaser && GITS_CBASER_VALID)))
> + its->enabled = false;
> +

uh, why don't we check these conditions before we enable the ITS instead
of enabling, checking, and then disabling?

Thanks,
-Christoffer

> + /*
> * Try to process any pending commands. This function bails out early
> * if the ITS is disabled or no commands have been queued.
> */
> --
> 2.5.5
>