Re: [PATCH v2 05/11] KVM: arm/arm64: Make vgic_v3_check_base more broadly usable

Auger Eric
2017-05-09T09:42:06Z

Hi Christoffer,

On 09/05/2017 10:56, Christoffer Dall wrote:
> As we are about to fiddle with the IO device registration mechanism,
> let's be a little more careful when setting base addresses as early as
> possible. When setting a base address, we can check that there's
> address space enough for its scope and when the last of the two
> base addresses (dist and redist) get set, we can also check if the
> regions overlap at that time.
>
> This allows us to provide error messages to the user at time when trying
> to set the base address, as opposed to later when trying to run the VM.
>
> To do this, we make vgic_v3_check_base available in the core vgic-v3
> code as well as in the other parts of the GICv3 code, namely the MMIO
> config code.
>
> We also return true for undefined base addresses so that the function
> can be used before all base addresses are set; all callers already check
> for uninitialized addresses before calling this function.
>
> Signed-off-by: Christoffer Dall <cdall@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
> virt/kvm/arm/vgic/vgic-v3.c | 19 +++++++++++++++----
> virt/kvm/arm/vgic/vgic.h | 1 +
> 2 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index 12e52a0..2d53d7a 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -329,19 +329,30 @@ int vgic_v3_save_pending_tables(struct kvm *kvm)
> return 0;
> }
>
> -/* check for overlapping regions and for regions crossing the end of memory */
> -static bool vgic_v3_check_base(struct kvm *kvm)
> +/*
> + * Check for overlapping regions and for regions crossing the end of memory
> + * for base addresses which have already been set.
> + */
> +bool vgic_v3_check_base(struct kvm *kvm)
> {
> struct vgic_dist *d = &kvm->arch.vgic;
> gpa_t redist_size = KVM_VGIC_V3_REDIST_SIZE;
>
> redist_size *= atomic_read(&kvm->online_vcpus);
>
> - if (d->vgic_dist_base + KVM_VGIC_V3_DIST_SIZE < d->vgic_dist_base)
> + if (!IS_VGIC_ADDR_UNDEF(d->vgic_dist_base) &&
> + d->vgic_dist_base + KVM_VGIC_V3_DIST_SIZE < d->vgic_dist_base)
> return false;
> - if (d->vgic_redist_base + redist_size < d->vgic_redist_base)
> +
> + if (!IS_VGIC_ADDR_UNDEF(d->vgic_redist_base) &&
> + d->vgic_redist_base + redist_size < d->vgic_redist_base)
> return false;
>
> + /* Both base addresses must be set to check if they overlap */
> + if (IS_VGIC_ADDR_UNDEF(d->vgic_dist_base) ||
> + IS_VGIC_ADDR_UNDEF(d->vgic_redist_base))
> + return true;
> +
> if (d->vgic_dist_base + KVM_VGIC_V3_DIST_SIZE <= d->vgic_redist_base)
> return true;
> if (d->vgic_redist_base + redist_size <= d->vgic_dist_base)
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index a2aeaa8..89eb935 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -175,6 +175,7 @@ int vgic_v3_map_resources(struct kvm *kvm);
> int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq);
> int vgic_v3_save_pending_tables(struct kvm *kvm);
> int vgic_register_redist_iodevs(struct kvm *kvm);
> +bool vgic_v3_check_base(struct kvm *kvm);
>
> void vgic_v3_load(struct kvm_vcpu *vcpu);
> void vgic_v3_put(struct kvm_vcpu *vcpu);
>