From: Jason Gunthorpe <jgg@nvidia.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
"cohuck@redhat.com" <cohuck@redhat.com>,
"corbet@lwn.net" <corbet@lwn.net>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"farman@linux.ibm.com" <farman@linux.ibm.com>,
"mjrosato@linux.ibm.com" <mjrosato@linux.ibm.com>,
"pasic@linux.ibm.com" <pasic@linux.ibm.com>,
"Lu, Baolu" <baolu.lu@intel.com>
Subject: Re: [RFC PATCH] vfio: Update/Clarify migration uAPI, add NDMA state
Date: Tue, 4 Jan 2022 12:09:59 -0400 [thread overview]
Message-ID: <20220104160959.GJ2328285@nvidia.com> (raw)
In-Reply-To: <BN9PR11MB5276145C1D82FAFBDCF70AEF8C4A9@BN9PR11MB5276.namprd11.prod.outlook.com>
On Tue, Jan 04, 2022 at 03:49:07AM +0000, Tian, Kevin wrote:
> btw can you elaborate the DOS concern? The device is assigned
> to an user application, which has one thread (migration thread)
> blocked on another thread (vcpu thread) when transiting the
> device to NDMA state. What service outside of this application
> is denied here?
The problem is the VM controls when the vPRI is responded and
migration cannot proceed until this is done.
So the basic DOS is for a hostile VM to trigger a vPRI and then never
answer it. Even trivially done from userspace with a vSVA and
userfaultfd, for instance.
This will block the hypervisor from ever migrating the VM in a very
poor way - it will just hang in the middle of a migration request.
Regardless of the complaints of the IP designers, this is a very poor
direction.
Progress in the hypervisor should never be contingent on a guest VM.
Jason
next prev parent reply other threads:[~2022-01-04 16:10 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-09 23:34 [RFC PATCH] vfio: Update/Clarify migration uAPI, add NDMA state Alex Williamson
2021-12-10 1:25 ` Jason Gunthorpe
2021-12-13 20:40 ` Alex Williamson
2021-12-14 12:08 ` Cornelia Huck
2021-12-14 16:26 ` Jason Gunthorpe
2021-12-20 22:26 ` Alex Williamson
2022-01-04 20:28 ` Jason Gunthorpe
2022-01-06 18:17 ` Alex Williamson
2022-01-06 21:20 ` Jason Gunthorpe
2022-01-10 7:55 ` Tian, Kevin
2022-01-10 17:34 ` Alex Williamson
2022-01-11 2:41 ` Tian, Kevin
2022-01-10 18:11 ` Jason Gunthorpe
2022-01-11 3:14 ` Tian, Kevin
2022-01-11 18:19 ` Jason Gunthorpe
2022-01-04 3:49 ` Tian, Kevin
2022-01-04 16:09 ` Jason Gunthorpe [this message]
2022-01-05 1:59 ` Tian, Kevin
2022-01-05 12:45 ` Jason Gunthorpe
2022-01-06 6:32 ` Tian, Kevin
2022-01-06 15:42 ` Jason Gunthorpe
2022-01-07 0:00 ` Tian, Kevin
2022-01-07 0:29 ` Jason Gunthorpe
2022-01-07 2:01 ` Tian, Kevin
2022-01-07 17:23 ` Jason Gunthorpe
2022-01-10 3:14 ` Tian, Kevin
2022-01-10 17:52 ` Jason Gunthorpe
2022-01-11 2:57 ` Tian, Kevin
2022-01-05 3:06 ` Tian, Kevin
2021-12-20 17:38 ` Cornelia Huck
2021-12-20 22:49 ` Alex Williamson
2021-12-21 11:24 ` Cornelia Huck
2022-01-07 8:03 ` Tian, Kevin
2022-01-07 16:36 ` Alex Williamson
2022-01-10 6:01 ` Tian, Kevin
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