From: Paul Durrant <Paul.Durrant@citrix.com>
To: 'Jan Beulich' <JBeulich@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.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 v4 01/15] re-work commit 3e06b989 "IOMMU: make page table population preemptible"...
Date: Thu, 2 Aug 2018 08:02:30 +0000 [thread overview]
Message-ID: <74e395deae9549c3a05fccb1241c35ae@AMSPEX02CL03.citrite.net> (raw)
In-Reply-To: <5B62B09A02000078001DA278@prv1-mh.provo.novell.com>
> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: 02 August 2018 08:20
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: Julien Grall <julien.grall@arm.com>; Andrew Cooper
> <Andrew.Cooper3@citrix.com>; Wei Liu <wei.liu2@citrix.com>; George
> Dunlap <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>;
> Stefano Stabellini <sstabellini@kernel.org>; xen-devel <xen-
> devel@lists.xenproject.org>; Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com>; Tim (Xen.org) <tim@xen.org>
> Subject: Re: [PATCH v4 01/15] re-work commit 3e06b989 "IOMMU: make
> page table population preemptible"...
>
> >>> On 01.08.18 at 15:40, <paul.durrant@citrix.com> wrote:
> > ...to simplify the implementation and turn need_iommu back into a
> boolean.
> >
> > As noted in [1] the tri-state nature of need_iommu after commit 3e06b989
> is
> > confusing, as is the implementation of pre-emption using relmem_list.
> >
> > This patch instead uses a simple count of pages already populated stored in
> > the x86 variant of struct arch_iommu and skips over that number of pages
> > if arch_iommu_populate_page_table() is re-invoked after pre-emption.
>
> Well, yes, I would have used that model in said commit if it was reliable,
> but it isn't: What if the list of pages changed between two (re-)invocations?
Is that really going to happen? This is the result of a domctl, which is a tools-only hypercall right?
> Furthermore, with huge enough a guest even the skipping of the already
> processed several million pages may exhaust the time acceptable between
> preemption points.
Ok, I'll keep a pointer into the page list instead.
Paul
>
> Jan
>
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next prev parent reply other threads:[~2018-08-02 8:02 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-01 13:40 [PATCH v4 00/15] paravirtual IOMMU interface Paul Durrant
2018-08-01 13:40 ` [PATCH v4 01/15] re-work commit 3e06b989 "IOMMU: make page table population preemptible" Paul Durrant
2018-08-01 16:15 ` Roger Pau Monné
2018-08-02 10:26 ` Paul Durrant
2018-08-02 7:19 ` Jan Beulich
2018-08-02 8:02 ` Paul Durrant [this message]
2018-08-02 8:04 ` Paul Durrant
2018-08-02 8:18 ` Jan Beulich
2018-08-02 8:49 ` Paul Durrant
2018-08-02 10:01 ` Jan Beulich
2018-08-01 13:40 ` [PATCH v4 02/15] iommu: introduce the concept of BFN Paul Durrant
2018-08-01 13:40 ` [PATCH v4 03/15] iommu: make use of type-safe BFN and MFN in exported functions Paul Durrant
2018-08-01 13:40 ` [PATCH v4 04/15] iommu: push use of type-safe BFN and MFN into iommu_ops Paul Durrant
2018-08-01 13:40 ` [PATCH v4 05/15] iommu: don't domain_crash() inside iommu_map/unmap_page() Paul Durrant
2018-08-01 13:40 ` [PATCH v4 06/15] public / x86: introduce __HYPERCALL_iommu_op Paul Durrant
2018-08-01 13:40 ` [PATCH v4 07/15] iommu: track reserved ranges using a rangeset Paul Durrant
2018-08-01 13:40 ` [PATCH v4 08/15] x86: add iommu_op to query reserved ranges Paul Durrant
2018-08-01 13:40 ` [PATCH v4 09/15] vtd: add lookup_page method to iommu_ops Paul Durrant
2018-08-01 13:40 ` [PATCH v4 10/15] mm / iommu: include need_iommu() test in iommu_use_hap_pt() Paul Durrant
2018-08-01 13:40 ` [PATCH v4 11/15] mm / iommu: split need_iommu() into has_iommu_pt() and sync_iommu_pt() Paul Durrant
2018-08-01 13:40 ` [PATCH v4 12/15] x86: add iommu_op to enable modification of IOMMU mappings Paul Durrant
2018-08-01 13:40 ` [PATCH v4 13/15] memory: add get_paged_gfn() as a wrapper Paul Durrant
2018-08-01 13:40 ` [PATCH v4 14/15] x86: add iommu_ops to modify and flush IOMMU mappings Paul Durrant
2018-08-01 13:40 ` [PATCH v4 15/15] x86: extend the map and unmap iommu_ops to support grant references Paul Durrant
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