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From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Paul Durrant <paul.durrant@citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	George Dunlap <george.dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
	Julien Grall <julien.grall@arm.com>,
	Jan Beulich <jbeulich@suse.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v4 01/15] re-work commit 3e06b989 "IOMMU: make page table population preemptible"...
Date: Wed, 1 Aug 2018 18:15:17 +0200	[thread overview]
Message-ID: <20180801161517.kg3diasbulao6jei@mac> (raw)
In-Reply-To: <20180801134028.1654-2-paul.durrant@citrix.com>

On Wed, Aug 01, 2018 at 02:40:14PM +0100, Paul Durrant 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.

Urg, all this is quite ugly. It would be quite better if the need for
an IOMMU was decided before populating the p2m (ie: at domain_create
time by passing an extra XEN_DOMCTL_CDF_iommu or some such), so that
the normal addition of RAM would also populate the IOMMU page tables
if not shared.

> [1] https://lists.xenproject.org/archives/html/xen-devel/2018-07/msg01870.html
> 
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

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  reply	other threads:[~2018-08-01 16:15 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 [this message]
2018-08-02 10:26     ` Paul Durrant
2018-08-02  7:19   ` Jan Beulich
2018-08-02  8:02     ` Paul Durrant
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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