On Thu, 6 Feb 2025 at 14:23, Eric Auger <eric.au...@redhat.com> wrote:
>
> Currently the iommu may be reset before the devices
> it protects. For example this happens with virtio-scsi-pci.
> when system_reset is issued from qmp monitor, spurious
> "virtio: zero sized buffers are not allowed" warnings can
> be observed.
>
> Signed-off-by: Eric Auger <eric.au...@redhat.com>
> ---
> hw/arm/smmuv3.c | 9 +++++----
> hw/arm/trace-events | 1 +
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> index c0cf5df0f6..7522c32b24 100644
> --- a/hw/arm/smmuv3.c
> +++ b/hw/arm/smmuv3.c
> @@ -1870,13 +1870,14 @@ static void smmu_init_irq(SMMUv3State *s,
> SysBusDevice *dev)
> }
> }
>
> -static void smmu_reset_hold(Object *obj, ResetType type)
> +static void smmu_reset_exit(Object *obj, ResetType type)
> {
> SMMUv3State *s = ARM_SMMUV3(obj);
> SMMUv3Class *c = ARM_SMMUV3_GET_CLASS(s);
>
> - if (c->parent_phases.hold) {
> - c->parent_phases.hold(obj, type);
> + trace_smmu_reset_exit();
> + if (c->parent_phases.exit) {
> + c->parent_phases.exit(obj, type);
> }
If we need to do something unexpected like reset
register values in the exit phase rather than the
hold phase, it's a good idea to have a comment explaining
why, to avoid somebody coming along afterwards and tidying
it up into the more usual arrangement.
If I understand correctly we need to keep the whole IOMMU
config intact until the exit phase? What's the thing the
device behind the IOMMU is trying to do during its reset
that triggers the warning?
thanks
-- PMM
