From: Paul Durrant <Paul.Durrant@citrix.com>
To: 'Jan Beulich' <JBeulich@suse.com>, Kevin Tian <kevin.tian@intel.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
Julien Grall <julien.grall@arm.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Subject: Re: [PATCH v6 01/14] iommu: introduce the concept of BFN...
Date: Wed, 5 Sep 2018 09:13:01 +0000 [thread overview]
Message-ID: <a3315f3d139b4484a71c9669bd312fe1@AMSPEX02CL03.citrite.net> (raw)
In-Reply-To: <5B8F81B302000078001E55C9@prv1-mh.provo.novell.com>
> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: 05 September 2018 08:12
> To: Kevin Tian <kevin.tian@intel.com>
> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>; Julien Grall
> <julien.grall@arm.com>; Paul Durrant <Paul.Durrant@citrix.com>; Stefano
> Stabellini <sstabellini@kernel.org>; xen-devel <xen-
> devel@lists.xenproject.org>
> Subject: RE: [Xen-devel] [PATCH v6 01/14] iommu: introduce the concept of
> BFN...
>
> >>> On 05.09.18 at 08:56, <kevin.tian@intel.com> wrote:
> >> From: Jan Beulich [mailto:JBeulich@suse.com]
> >> Sent: Wednesday, September 5, 2018 2:49 PM
> >>
> >> >>> On 05.09.18 at 02:42, <kevin.tian@intel.com> wrote:
> >> >> From: Jan Beulich [mailto:JBeulich@suse.com]
> >> >> Sent: Tuesday, September 4, 2018 5:08 PM
> >> >>
> >> >> >>> On 04.09.18 at 10:49, <Paul.Durrant@citrix.com> wrote:
> >> >> >> -----Original Message-----
> >> >> >> From: Jan Beulich [mailto:JBeulich@suse.com]
> >> >> >> Sent: 04 September 2018 09:47
> >> >> >> To: Kevin Tian <kevin.tian@intel.com>
> >> >> >> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>;
> Julien
> >> >> Grall
> >> >> >> <julien.grall@arm.com>; Paul Durrant <Paul.Durrant@citrix.com>;
> >> >> Stefano
> >> >> >> Stabellini <sstabellini@kernel.org>; xen-devel <xen-
> >> >> >> devel@lists.xenproject.org>
> >> >> >> Subject: Re: [Xen-devel] [PATCH v6 01/14] iommu: introduce the
> >> concept
> >> >> of
> >> >> >> BFN...
> >> >> >>
> >> >> >> >>> On 04.09.18 at 10:37, <kevin.tian@intel.com> wrote:
> >> >> >> >> From: Jan Beulich [mailto:JBeulich@suse.com]
> >> >> >> >> Sent: Tuesday, September 4, 2018 4:33 PM
> >> >> >> >> >
> >> >> >> >> > bus address is commonly used along with physical/virtual
> >> address,
> >> >> to
> >> >> >> >> > represent different views between devices and CPU. From
> that
> >> >> angle
> >> >> >> >> > I think BFN is a clear term in this context. btw it is not
> necessary
> >> to
> >> >> >> >> > differentiate GBFN and MBFN since there is only one BFN view
> >> per
> >> >> >> >> > device.
> >> >> >> >>
> >> >> >> >> Sure, but you neglect the presence of one or more IOMMUs
> when
> >> >> >> >> you say "between devices and CPU". There addresses prior to
> and
> >> >> >> >> after IOMMU translation are distinct, and while the one before
> the
> >> >> >> >> translation matches the device view, the one after translation
> does
> >> >> >> >> not necessarily match the CPU view. Hence there are two "bus"
> >> >> >> >> frame numbers here - one representing the device view, and
> the
> >> >> >> >> other representing the IOMMU (output) view.
> >> >> >> >>
> >> >> >> >
> >> >> >> > I didn't get. the output address from IOMMU is the one sent to
> >> >> >> > memory controller, same as the one sent from CPU.
> >> >> >>
> >> >> >> That's on present x86 systems, but aiui not in the general case. The
> >> >> >> terminology to be used in Xen should fit the general case though.
> >> >> >
> >> >> > So your concern is cascaded IOMMUs?
> >> >>
> >> >> Not primarily. My concern are systems with an I/O address space
> >> >> (behind the IOMMU) distinct from the CPU address space. Iirc at
> >> >> least Alpha is/was that way.
> >> >>
> >> >
> >> > Then Paul please documents clearly that this bus address refers to
> >> > the input side of IOMMU. :-)
> >>
> >> But when reading code you can't always go back to look at the one
> >> place where its meaning is documented. Hence my desire for a name
> >> which properly conveys the meaning.
> >>
> >
> > Then possibly go back to DFN, but take 'D' as DMA instead of device?
>
> How would "DMA" be any better than "bus"? Whose view it is then still
> is unclear.
>
Personally I think 'bus address' is commonly enough used term for addresses used by devices for DMA. Indeed we have already 'dev_bus_addr' in the grant map and unmap hypercalls. So baddr and bfn seem like ok terms to me. It's also not impossible to rename these later if they prove problematic.
Paul
> Jan
>
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
next prev parent reply other threads:[~2018-09-05 9:13 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a3315f3d139b4484a71c9669bd312fe1@AMSPEX02CL03.citrite.net \
--to=paul.durrant@citrix.com \
--cc=JBeulich@suse.com \
--cc=julien.grall@arm.com \
--cc=kevin.tian@intel.com \
--cc=sstabellini@kernel.org \
--cc=suravee.suthikulpanit@amd.com \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).