linux-kernel - Re: [PATCH v2 06/19] iommufd/viommu: Add IOMMU_VIOMMU_SET/UNSET_VDEV

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aBppFi7eKngFipps@nvidia.com>
Date: Tue, 6 May 2025 12:55:02 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: Alexey Kardashevskiy <aik@....com>, <kevin.tian@...el.com>,
	<will@...nel.org>, <joro@...tes.org>, <suravee.suthikulpanit@....com>,
	<robin.murphy@....com>, <dwmw2@...radead.org>, <baolu.lu@...ux.intel.com>,
	<shuah@...nel.org>, <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kselftest@...r.kernel.org>,
	<eric.auger@...hat.com>, <jean-philippe@...aro.org>, <mdf@...nel.org>,
	<mshavit@...gle.com>, <shameerali.kolothum.thodi@...wei.com>,
	<smostafa@...gle.com>, <yi.l.liu@...el.com>
Subject: Re: [PATCH v2 06/19] iommufd/viommu: Add
 IOMMU_VIOMMU_SET/UNSET_VDEV_ID ioctl

On Tue, May 06, 2025 at 09:58:47AM -0300, Jason Gunthorpe wrote:
> On Mon, May 05, 2025 at 07:53:44PM -0700, Nicolin Chen wrote:
> > On Mon, May 05, 2025 at 02:08:07PM -0300, Jason Gunthorpe wrote:
> > > On Wed, Apr 30, 2025 at 12:58:47AM -0700, Nicolin Chen wrote:
> > > The bus numbers can be reassigned at any time on the fly by the guest
> > > by reprogramming the PCI hierarchy.
> > 
> > Yes. If we take some aggressive use case into account, where its
> > BDF number could change multiple times, I think it's natural for
> > VMM to simply destroy the previous vDEVICE and allocate a new one
> > with a new BDF number, right?
> 
> We should not destroy the vdevice for something like that. In a CC
> case that would unplug it from the VM which is not right.

CC needs BDF to allocate a VDEV in the CC world. So, it cannot
allocate a VDEV with BDF=0 firstly, which is what Alex reported.

And even for a normal case that the device is migrating between
PCI buses, CC might not be able to update the BDF (which can be
a part of CC_VDEV_ALLOC instruction), even if iommufd supports
an update ioctl. So, the underlying handler for an update ioctl
is still to first destroy the VDEV and re-allocate a new one?

Thanks
Nicolin