[v2,0/3] Fix MSI-X handling for Xen HVM

Message

Marek Marczykowski-Górecki April 30, 2024, 5:33 p.m. UTC

This series fixes handling MSI-X when device model is running in a stubdomain.
The main part is to avoid accessing /dev/mem, which also fixes running dom0
with lockdown enabled.

It depends on a behavior change of Xen that was just comitted, and signaled
with a feature flag. If Xen is too old (and XENFEAT_dm_msix_all_writes flag is
not set), fallback to the old behavior.

The other part is a fix to enforce read-only registers in the config space.
This fixes MSI-X setup for iwlwifi Linux driver, as it happen to write to MSI-X
capability id reg (as a workaround for some older device which has another
register there). It should be no-op, but due to a bug in xen_pt code,
it broke MSI-X detection.

All those patches have been shipped in Qubes OS 4.2 already, and prove to fix
the issue.

See individual commit messages for details.

Marek Marczykowski-Górecki (3):
  hw/xen/xen_pt: Save back data only for declared registers
  Update Xen's features.h header
  Do not access /dev/mem in MSI-X PCI passthrough on Xen

 hw/xen/xen_pt.c                     | 24 +++++++-
 hw/xen/xen_pt_msi.c                 | 94 ++++++++++++++++++------------
 include/hw/xen/interface/features.h | 17 +++++-
 3 files changed, 99 insertions(+), 36 deletions(-)

base-commit: 2358f1b60f73287fe606c7ff48043b4f9e1c2d0f