Re: [PATCH 0/5] Fix vIOMMU reset order

[Peter Xu <peterx@redhat.com>]

On Thu, Feb 06, 2025 at 03:21:51PM +0100, Eric Auger wrote:
> This is a follow-up of Peter's attempt to fix the fact that
> vIOMMUs are likely to be reset before the device they protect:
> 
> [PATCH 0/4] intel_iommu: Reset vIOMMU after all the rest of devices
> https://lore.kernel.org/all/20240117091559.144730-1-peterx@redhat.com/
> 
> This is especially observed with virtio devices when a qmp system_reset
> command is sent but also with VFIO devices.
> 
> This series puts the vIOMMU reset in the 3-phase exit callback.
> 
> This scheme was tested successful with virtio-devices and some
> VFIO devices. Nevertheless not all the topologies have been
> tested yet.

Eric,

It's great to know that we seem to be able to fix everything in such small
changeset!

I would like to double check two things with you here:

  - For VFIO's reset hook, looks like we have landed more changes so that
    vfio's reset function is now a TYPE_LEGACY_RESET, and it always do the
    reset during "hold" phase only (via legacy_reset_hold()).  That part
    will make sure vIOMMU (if switching to exit()-only reset) will order
    properly with VFIO.  Is my understanding correct here?

  - Is it possible if some PCIe devices that will provide its own
    phase.exit(), would it matter on the order of PCIe device's
    phase.exit() and vIOMMU's phase.exit() (if vIOMMUs switch to use
    exit()-only approach like this one)?

PS: it would be great to attach such information in either cover letter or
commit message.  But definitely not a request to repost the patchset, if
Michael would have Message-ID when merge that'll be far enough to help
anyone find this discussion again.

Thanks!

-- 
Peter Xu