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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Alex Williamson <alex.williamson@redhat.com>
CC: "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "eric.auger@redhat.com"
	<eric.auger@redhat.com>, "clg@redhat.com" <clg@redhat.com>, "Chatre,
 Reinette" <reinette.chatre@intel.com>, "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 2/7] vfio/pci: Lock external INTx masking ops
Thread-Topic: [PATCH 2/7] vfio/pci: Lock external INTx masking ops
Thread-Index: AQHacAtesjvk+OVhZUWmMSfK5TxB5rEr9L/QgADFPYCAALcQwA==
Date: Fri, 8 Mar 2024 07:17:12 +0000
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> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Friday, March 8, 2024 4:21 AM
>=20
> On Thu, 7 Mar 2024 08:37:53 +0000
> "Tian, Kevin" <kevin.tian@intel.com> wrote:
>=20
> > > From: Alex Williamson <alex.williamson@redhat.com>
> > > Sent: Thursday, March 7, 2024 5:15 AM
> > >
> > > Mask operations through config space changes to DisINTx may race INTx
> > > configuration changes via ioctl.  Create wrappers that add locking fo=
r
> > > paths outside of the core interrupt code.
> > >
> > > In particular, irq_type is updated holding igate, therefore testing
> > > is_intx() requires holding igate.  For example clearing DisINTx from
> > > config space can otherwise race changes of the interrupt configuratio=
n.
> > >
> >
> > Looks the suspend path still checks irq_type w/o holding igate:
> >
> > 	vdev->pm_intx_masked =3D ((vdev->irq_type =3D=3D
> VFIO_PCI_INTX_IRQ_INDEX) &&
> > 				 vfio_pci_intx_mask(vdev));
> >
> > Is it with assumption that no change of configuration is possible at
> > that point?
>=20
> Yes, I believe this is relatively safe because userspace is frozen at
> this point.  That's not however to claim that irq_type is absolutely
> used consistently after this series.  I just didn't see the other
> violations rise to the same level as the fixes in this series and
> wanted to avoid the distraction.  I've stashed a number of patches that
> I'd eventually like to post as follow-ups to this series.  Thanks,
>=20

Reviewed-by: Kevin Tian <kevin.tian@intel.com>