Re: [PATCH v2 02/10] KVM: arm/arm64: vgic-its: Always allow clearing GITS_CREADR/CWRITER

Andre Przywara
2017-10-06T14:37:35Z

Hi,

On 27/09/17 14:28, Eric Auger wrote:
> If the GITS_CBASER Size field is 0, which can correspond to a
> reset value, the userspace fails to set the GITS_CREADR/CWRITER
> offsets to 0. This failure is not justified.
>
> Let's allow this setting which can also correspond to a reset value.

But the GITS_CBASER size field has a +1 encoding, so can never be 0, if
I understand the manual (and ITS_CMD_BUFFER_SIZE) correctly.

What am I missing here?

Cheers,
Andre.

> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
>
> need to CC stable
> ---
> virt/kvm/arm/vgic/vgic-its.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index fbbc97b..76bed2d 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1329,7 +1329,7 @@ static void vgic_mmio_write_its_cwriter(struct kvm *kvm, struct vgic_its *its,
>
> reg = update_64bit_reg(its->cwriter, addr & 7, len, val);
> reg = ITS_CMD_OFFSET(reg);
> - if (reg >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
> + if (reg && reg >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
> mutex_unlock(&its->cmd_lock);
> return;
> }
> @@ -1370,7 +1370,7 @@ static int vgic_mmio_uaccess_write_its_creadr(struct kvm *kvm,
> }
>
> cmd_offset = ITS_CMD_OFFSET(val);
> - if (cmd_offset >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
> + if (cmd_offset && cmd_offset >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
> ret = -EINVAL;
> goto out;
> }
>