linux-kernel - RE: [PATCH v4 02/11] iommufd: Introduce IOMMUFD_OBJ

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: <BN9PR11MB527624ABC2E5D1E4C7AC23208C4A2@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Mon, 28 Oct 2024 02:30:22 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: Baolu Lu <baolu.lu@...ux.intel.com>, Nicolin Chen <nicolinc@...dia.com>,
	"will@...nel.org" <will@...nel.org>, "joro@...tes.org" <joro@...tes.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	"robin.murphy@....com" <robin.murphy@....com>, "dwmw2@...radead.org"
	<dwmw2@...radead.org>, "shuah@...nel.org" <shuah@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kselftest@...r.kernel.org"
	<linux-kselftest@...r.kernel.org>, "eric.auger@...hat.com"
	<eric.auger@...hat.com>, "jean-philippe@...aro.org"
	<jean-philippe@...aro.org>, "mdf@...nel.org" <mdf@...nel.org>,
	"mshavit@...gle.com" <mshavit@...gle.com>,
	"shameerali.kolothum.thodi@...wei.com"
	<shameerali.kolothum.thodi@...wei.com>, "smostafa@...gle.com"
	<smostafa@...gle.com>, "Liu, Yi L" <yi.l.liu@...el.com>, "aik@....com"
	<aik@....com>, "zhangfei.gao@...aro.org" <zhangfei.gao@...aro.org>,
	"patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: RE: [PATCH v4 02/11] iommufd: Introduce IOMMUFD_OBJ_VIOMMU and its
 related struct

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Friday, October 25, 2024 11:24 PM
> 
> On Fri, Oct 25, 2024 at 08:47:40AM +0000, Tian, Kevin wrote:
> > > From: Jason Gunthorpe <jgg@...dia.com>
> > > Sent: Tuesday, October 22, 2024 9:16 PM
> > >
> > > On Tue, Oct 22, 2024 at 04:59:07PM +0800, Baolu Lu wrote:
> > >
> > > > Is it feasible to make vIOMMU object more generic, rather than strictly
> > > > tying it to nested translation? For example, a normal paging domain
> that
> > > > translates gPAs to hPAs could also have a vIOMMU object associated
> with
> > > > it.
> > > >
> > > > While we can only support vIOMMU object allocation uAPI for S2 paging
> > > > domains in the context of this series, we could consider leaving the
> > > > option open to associate a vIOMMU object with other normal paging
> > > > domains that are not a nested parent?
> > >
> > > Why? The nested parent flavour of the domain is basically free to
> > > create, what reason would be to not do that?
> > >
> > > If the HW doesn't support it, then does the HW really need/support a
> > > VIOMMU?
> >
> > Now it's agreed to build trusted I/O on top of this new vIOMMU object.
> > format-wise probably it's free to assume that nested parent is supported
> > on any new platform which will support trusted I/O. But I'm not sure
> > all the conditions around allowing nested are same as for trusted I/O,
> > e.g. for ARM nesting is allowed only for CANWBS/S2FWB. Are they
> > always guaranteed in trusted I/O configuration?
> 
> ARM is a big ? what exactly will come, but I'm expecting that to be
> resolved either with continued HW support or Linux will add the cache
> flushing and relax the test.
> 
> > Baolu did raise a good open to confirm given it will be used beyond
> > nesting. 😊
> 
> Even CC is "nesting", it is just nested with a fixed Identity S1 in
> the baseline case. The S2 translation still exists and still has to be
> consistent with whatever the secure world is doing.

this is true. That is why I asked more from the conditions around
enabling nested instead of the translation/format itself. 

> 
> So, my feeling is that the S2 nested domain is mandatory for the
> viommu, especially for CC, it must exists. In the end there may be
> more options than just a nested parent.
> 
> For instance if the CC design relies on the secure world sharing the
> CPU and IOMMU page table we might need a new HWPT type to represent
> that configuration.
> 
> From a uapi perspective we seem OK here as the hwpt input could be
> anything. We might have to adjust some checks in the kernel someday.
> 

yes, that could be extended in case of a need.