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From: Yinghan Yang via iommu <iommu@lists.linux-foundation.org>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: "kevin.tian@intel.com" <kevin.tian@intel.com>,
	"mst@redhat.com" <mst@redhat.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"Boeuf, Sebastien" <sebastien.boeuf@intel.com>,
	Alexander Grest <Alexander.Grest@microsoft.com>,
	"ahs3@redhat.com" <ahs3@redhat.com>
Subject: RE: [EXTERNAL] Re: Question regarding VIOT proposal
Date: Thu, 3 Dec 2020 22:21:43 +0000	[thread overview]
Message-ID: <MW2PR2101MB11301F2185D1C9016310728E80F21@MW2PR2101MB1130.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20201106135745.GB974750@myrica>

Hi Jean,

I'm sorry for the delayed response. I think the new "PCI range node" description makes sense. Could you please make this change in the proposal?

Other than that, the proposal looks good to go.

Thanks,
Yinghan

-----Original Message-----
From: Jean-Philippe Brucker <jean-philippe@linaro.org> 
Sent: Friday, November 6, 2020 5:58 AM
To: Yinghan Yang <Yinghan.Yang@microsoft.com>
Cc: iommu@lists.linux-foundation.org; Alexander Grest <Alexander.Grest@microsoft.com>; eric.auger@redhat.com; joro@8bytes.org; kevin.tian@intel.com; lorenzo.pieralisi@arm.com; mst@redhat.com; Boeuf, Sebastien <sebastien.boeuf@intel.com>; ahs3@redhat.com
Subject: Re: [EXTERNAL] Re: Question regarding VIOT proposal

Hi Yinghan,

On Thu, Nov 05, 2020 at 10:05:28PM +0000, Yinghan Yang wrote:
> Thank you for the clarifications. In cases where a large range of  PCI segments may be assigned to guest, would it make sense to describe this configuration as base + count. Currently, one would have to describe them individually. 

Yes, I've been wondering whether that would be useful. It would also allow hotplugging new segments, if that's ever needed. It requires changing the enumeration rule that derives an endpoint ID from segment + BDF number.

First, when describing a range of segments, are BFD start and end still valid?  Do they only apply to first and last segment respectively?  To keep things simple I think BDF start/end should keep the same meaning:
valid regardless of segment range, and apply to all segments in the range.

So the new PCI Range node could be:

Field                   Length  Offset  Description
-------------------------------------------------------------------------------
Type                    1       0       1 – PCI range
Reserved                1       1       0.
Length                  2       2       Length of the node in bytes.
Endpoint start          4       4       First endpoint ID.
PCI Segment start       2       8       First PCI Segment number in the range.
PCI Segment end         2       10      Last PCI Segment number in the range.
PCI BDF start           2       12      First Bus-Device-Function number in the range.
PCI BDF end             2       14      Last Bus-Device-Function number in the range.
Output node             2       16      Offset from the start of the table to the next translation element.
Reserved                6       18      0.

A PCI device is affected by the node if its segment is in [Segment start, Segment end], and if its BDF is in [BPF start, BDF end]. Its endpoint ID will be:

    ((Segment - Segment start) << 16) + BDF - BDF start + Endpoint start

Does that sound OK?

Thanks,
Jean

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  reply	other threads:[~2020-12-03 22:21 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-05  0:13 Question regarding VIOT proposal Yinghan Yang via iommu
2020-11-05 13:45 ` Jean-Philippe Brucker
2020-11-05 22:05   ` [EXTERNAL] " Yinghan Yang via iommu
2020-11-06 13:57     ` Jean-Philippe Brucker
2020-12-03 22:21       ` Yinghan Yang via iommu [this message]
2020-12-03 23:01         ` Al Stone
2020-12-04 18:09           ` Jean-Philippe Brucker
2020-12-04 18:15             ` Yinghan Yang via iommu
2020-12-04 20:18             ` Al Stone
2021-02-02  9:17               ` Jean-Philippe Brucker
2021-02-02 20:27                 ` Al Stone
2021-02-03  8:46                   ` Jean-Philippe Brucker
2021-02-04 20:25                     ` Al Stone
2021-02-16 21:31                       ` Al Stone
2021-02-17  9:37                         ` Jean-Philippe Brucker
2021-02-18 23:39                           ` Al Stone
2021-02-19 11:24                             ` Jean-Philippe Brucker
2021-02-19 17:35                               ` Al Stone

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