From: Paul Durrant <Paul.Durrant@citrix.com>
To: Kevin Tian <kevin.tian@intel.com>, 'Jan Beulich' <JBeulich@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Andrew Cooper <Andrew.Cooper3@citrix.com>,
"Tim (Xen.org)" <tim@xen.org>,
George Dunlap <George.Dunlap@citrix.com>,
Julien Grall <julien.grall@arm.com>,
Ian Jackson <Ian.Jackson@citrix.com>,
xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v6 13/14] x86: add iommu_ops to modify and flush IOMMU mappings
Date: Thu, 13 Sep 2018 08:32:57 +0000 [thread overview]
Message-ID: <4dc9ac0af8754f5b890dfc4c2cd59250@AMSPEX02CL03.citrite.net> (raw)
In-Reply-To: <AADFC41AFE54684AB9EE6CBC0274A5D191301AF0@SHSMSX101.ccr.corp.intel.com>
> -----Original Message-----
> From: Tian, Kevin [mailto:kevin.tian@intel.com]
> Sent: 13 September 2018 07:41
> To: Paul Durrant <Paul.Durrant@citrix.com>; 'Jan Beulich'
> <JBeulich@suse.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>; Wei Liu
> <wei.liu2@citrix.com>; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> Andrew Cooper <Andrew.Cooper3@citrix.com>; Tim (Xen.org)
> <tim@xen.org>; George Dunlap <George.Dunlap@citrix.com>; Julien Grall
> <julien.grall@arm.com>; xen-devel <xen-devel@lists.xenproject.org>; Ian
> Jackson <Ian.Jackson@citrix.com>
> Subject: RE: [PATCH v6 13/14] x86: add iommu_ops to modify and flush
> IOMMU mappings
>
> > From: Paul Durrant
> > Sent: Wednesday, September 12, 2018 4:02 PM
> >
> >
> > > In order to avoid shooting down all pre-existing RAM mappings - is
> > > there no way the page table entries could be marked to identify
> > > their origin?
> > >
> >
> > I don't know whether that is possible; I'll have to find specs for Intel and
> > AMD IOMMUs and see if they have PTE bits available for such a use.
>
> there are ignored bits
>
> >
> > > I also have another more general concern: Allowing the guest to
> > > manipulate its IOMMU page tables means that it can deliberately
> > > shatter large pages, growing the overall memory footprint of the
> > > domain. I'm hesitant to say this, but I'm afraid that resource
> > > tracking of such "behind the scenes" allocations might be a
> > > necessary prereq for the PV IOMMU work.
> > >
> >
> > Remember that PV-IOMMU is only available for dom0 as it stands (and that
> > is the only use-case that XenServer currently has) so I think that, whilst the
> > concern is valid, there is no need danger in putting the code without such
> > tracking. Such work can be deferred to making PV-IOMMU for de-
> privileged
> > guests... if that facility is needed.
> >
>
> I didn't get why this is PV-IOMMU specific. Guest can always manipulate
> guest CPU page table to shatter large pages too...
>
At the moment that is true. I guess Jan doesn't want to introduce another way for a guest to cause Xen to consume large amounts of memory.
Paul
> Thanks
> Kevin
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next prev parent reply other threads:[~2018-09-13 8:32 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-23 9:46 [PATCH v6 00/14] paravirtual IOMMU interface Paul Durrant
2018-08-23 9:46 ` [PATCH v6 01/14] iommu: introduce the concept of BFN Paul Durrant
2018-08-30 15:59 ` Jan Beulich
2018-09-03 8:23 ` Paul Durrant
2018-09-03 11:46 ` Jan Beulich
2018-09-04 6:48 ` Tian, Kevin
2018-09-04 8:32 ` Jan Beulich
2018-09-04 8:37 ` Tian, Kevin
2018-09-04 8:47 ` Jan Beulich
2018-09-04 8:49 ` Paul Durrant
2018-09-04 9:08 ` Jan Beulich
2018-09-05 0:42 ` Tian, Kevin
2018-09-05 6:48 ` Jan Beulich
2018-09-05 6:56 ` Tian, Kevin
2018-09-05 7:11 ` Jan Beulich
2018-09-05 9:13 ` Paul Durrant
2018-09-05 9:38 ` Jan Beulich
2018-09-06 10:36 ` Paul Durrant
2018-09-06 13:13 ` Jan Beulich
2018-09-06 14:54 ` Paul Durrant
2018-09-07 1:47 ` Tian, Kevin
2018-09-07 6:24 ` Jan Beulich
2018-09-07 8:13 ` Paul Durrant
2018-09-07 8:16 ` Tian, Kevin
2018-09-07 8:25 ` Paul Durrant
2018-08-23 9:46 ` [PATCH v6 02/14] iommu: make use of type-safe BFN and MFN in exported functions Paul Durrant
2018-09-04 10:29 ` Jan Beulich
2018-08-23 9:47 ` [PATCH v6 03/14] iommu: push use of type-safe BFN and MFN into iommu_ops Paul Durrant
2018-09-04 10:32 ` Jan Beulich
2018-08-23 9:47 ` [PATCH v6 04/14] iommu: don't domain_crash() inside iommu_map/unmap_page() Paul Durrant
2018-09-04 10:38 ` Jan Beulich
2018-09-04 10:39 ` Paul Durrant
2018-08-23 9:47 ` [PATCH v6 05/14] public / x86: introduce __HYPERCALL_iommu_op Paul Durrant
2018-09-04 11:50 ` Jan Beulich
2018-09-04 12:23 ` Paul Durrant
2018-09-04 12:55 ` Jan Beulich
2018-09-04 13:17 ` Paul Durrant
2018-09-07 10:52 ` Jan Beulich
2018-08-23 9:47 ` [PATCH v6 06/14] iommu: track reserved ranges using a rangeset Paul Durrant
2018-09-07 10:40 ` Jan Beulich
2018-09-11 9:28 ` Paul Durrant
2018-08-23 9:47 ` [PATCH v6 07/14] x86: add iommu_op to query reserved ranges Paul Durrant
2018-09-07 11:01 ` Jan Beulich
2018-09-11 9:34 ` Paul Durrant
2018-09-11 9:43 ` Jan Beulich
2018-09-13 6:11 ` Tian, Kevin
2018-08-23 9:47 ` [PATCH v6 08/14] vtd: add lookup_page method to iommu_ops Paul Durrant
2018-09-07 11:11 ` Jan Beulich
2018-09-07 12:36 ` Paul Durrant
2018-09-07 14:56 ` Jan Beulich
2018-09-07 15:24 ` Paul Durrant
2018-09-07 15:52 ` Jan Beulich
2018-09-12 8:31 ` Paul Durrant
2018-09-12 8:43 ` Jan Beulich
2018-09-12 8:45 ` Paul Durrant
2018-09-12 8:51 ` Paul Durrant
2018-09-12 8:53 ` Paul Durrant
2018-09-12 9:03 ` Jan Beulich
2018-09-12 9:05 ` Paul Durrant
2018-09-12 9:12 ` Jan Beulich
2018-09-12 9:15 ` Paul Durrant
2018-09-12 9:21 ` Jan Beulich
2018-09-12 9:30 ` Paul Durrant
2018-09-12 10:07 ` Jan Beulich
2018-09-12 10:09 ` Paul Durrant
2018-09-12 12:15 ` Jan Beulich
2018-09-12 12:22 ` Paul Durrant
2018-09-12 12:39 ` Jan Beulich
2018-09-12 12:53 ` Paul Durrant
2018-09-12 13:19 ` Jan Beulich
2018-09-12 13:25 ` Paul Durrant
2018-09-12 13:39 ` Jan Beulich
2018-09-12 13:43 ` Paul Durrant
2018-09-12 8:59 ` Jan Beulich
2018-08-23 9:47 ` [PATCH v6 09/14] mm / iommu: include need_iommu() test in iommu_use_hap_pt() Paul Durrant
2018-09-07 11:20 ` Jan Beulich
2018-09-11 9:39 ` Paul Durrant
2018-09-11 9:47 ` Jan Beulich
2018-09-13 6:23 ` Tian, Kevin
2018-09-13 8:34 ` Paul Durrant
2018-08-23 9:47 ` [PATCH v6 10/14] mm / iommu: split need_iommu() into has_iommu_pt() and need_iommu_pt_sync() Paul Durrant
2018-08-23 11:10 ` Razvan Cojocaru
2018-09-11 14:31 ` Jan Beulich
2018-09-11 15:40 ` Paul Durrant
2018-09-12 6:45 ` Jan Beulich
2018-09-12 8:07 ` Paul Durrant
2018-08-23 9:47 ` [PATCH v6 11/14] x86: add iommu_op to enable modification of IOMMU mappings Paul Durrant
2018-09-11 14:48 ` Jan Beulich
2018-09-11 15:52 ` Paul Durrant
2018-09-12 6:53 ` Jan Beulich
2018-09-12 8:04 ` Paul Durrant
2018-08-23 9:47 ` [PATCH v6 12/14] memory: add get_paged_gfn() as a wrapper Paul Durrant
2018-08-23 10:24 ` Julien Grall
2018-08-23 10:30 ` Paul Durrant
2018-09-11 14:56 ` Jan Beulich
2018-09-12 9:10 ` Paul Durrant
2018-09-12 9:15 ` Jan Beulich
2018-09-12 10:01 ` George Dunlap
2018-09-12 10:08 ` Paul Durrant
2018-09-12 10:10 ` Jan Beulich
2018-08-23 9:47 ` [PATCH v6 13/14] x86: add iommu_ops to modify and flush IOMMU mappings Paul Durrant
2018-09-11 15:15 ` Jan Beulich
2018-09-12 7:03 ` Jan Beulich
2018-09-12 8:02 ` Paul Durrant
2018-09-12 8:27 ` Jan Beulich
2018-09-13 6:41 ` Tian, Kevin
2018-09-13 8:32 ` Paul Durrant [this message]
2018-09-13 8:49 ` Jan Beulich
2018-08-23 9:47 ` [PATCH v6 14/14] x86: extend the map and unmap iommu_ops to support grant references Paul Durrant
2018-09-12 14:12 ` Jan Beulich
2018-09-12 16:28 ` Paul Durrant
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