From: "Michael S. Tsirkin" <mst@redhat.com>
To: Parav Pandit <parav@nvidia.com>
Cc: "virtio-dev@lists.oasis-open.org"
<virtio-dev@lists.oasis-open.org>,
"cohuck@redhat.com" <cohuck@redhat.com>,
"virtio-comment@lists.oasis-open.org"
<virtio-comment@lists.oasis-open.org>,
Shahaf Shuler <shahafs@nvidia.com>,
Satananda Burla <sburla@marvell.com>
Subject: Re: [virtio-comment] Re: [PATCH 07/11] transport-pci: Introduce transitional MMR device id
Date: Mon, 10 Apr 2023 06:18:44 -0400 [thread overview]
Message-ID: <20230410060842-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <PH0PR12MB5481097A6BE0F55E6F626935DC949@PH0PR12MB5481.namprd12.prod.outlook.com>
On Sun, Apr 09, 2023 at 03:15:01AM +0000, Parav Pandit wrote:
>
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Friday, April 7, 2023 11:51 AM
>
> > > 1. A non-transitional device will expose a capability (not a feature bit, but a
> > capability at transport level).
> >
> > Note that we can allow this capability in transitional devices too.
> > This is useful since IO bar might not be enabled even if present.
> >
> This capability exposure makes a device transitional in some sense.
not in the sense spec uses it at the moment: transitional devices
are those that legacy drivers can bind to. transitional drivers
btw are those that can bind to legacy devices.
perhaps suprisingly, a transitional driver using a transitional
device does not rely on any legacy spec at all, they will
use the standard interfaces.
> > > This capability indicates that, it supports legacy interface.
> > > Lets name it legacy_if_emulation for sake of this discussion.
> > > It is a two-way pci capability.
> > > Device reports it.
> > > And driver enables it. (Why two way and why driver needs to enable it,
> > described later in point #d below).
> > >
> > > Hence, such non transitional device does not need to comply to below listed
> > requirements #a and #b.
> > >
> > > a. A driver MUST accept VIRTIO_F_VERSION_1 if it is offered.
> > > (Because hypervisor driver is a passthrough driver; and legacy driver will not
> > accept this feature bit).
> >
> > This is not a device requirement at all.
> >
> Those this is written as driver requirement; a device expects this feature bit to be negotiated.
> What should device implementor do? It should allow driver to not negotiate bit, right?
>
> Which means, below line to be change:
>
> from:
> device MAY fail to operate further if VIRTIO_F_VERSION_1 is not accepted.
>
> to:
> Non transitional device that does not have legacy interface capability MAY fail to operate further if V_1 is not accepted.
> Non transitional device that has legacy interface capability SHOULD operate further even if V_1 is not accepted.
Look nothing changes with MMR capability at all.
We currently have:
A device MUST offer VIRTIO_F_VERSION_1. A device MAY fail to operate further
if VIRTIO_F_VERSION_1 is not accepted.
it's implied that this does not refer to legacy interface.
You want to clarify this adding to legacy interface section text
explaining that of course VIRTIO_F_VERSION_1 must not
be offered through that? Sure but it's a separate issue
from MMR capability. don't try to drink the ocean.
> > > b. device MAY fail to operate further if VIRTIO_F_VERSION_1 is not accepted.
> >
> > This is optional not a requirement.
> >
> Please see above wording, if its acceptable.
you don't need any of that for this effort, generally
VIRTIO_F_VERSION_1 thing needs a lot of work, if you
want to invest the time just ask I'll try to list the issues.
But nothing to do with memory mapped legacy interface
directly.
> > > c. A non-transitional device with above legacy_if_supported
> > > capability, will allow device reset sequence, described in [1] Driver
> > > Requirements: Device Initialization (3.1.1) [2] Legacy Interface:
> > > Device Initialization (3.1.2)
> > >
> > > > > device reset sequence.
> > > >
> > > > what is this one?
> > >
> > > I listed above in #c.
> > > And
> > >
> > > d. When legacy_if_emulation capability is offered and hypervisor driver
> > enabled it, when driver perform device reset, driver will not wait for device
> > reset to go zero.
> > > When legacy_if_emulation capability is not enabled by (hypervisor or other
> > say existing) driver, driver will wait for device reset to turn 0. (Following the
> > driver requirement 2.4.2).
> >
> > It might not be a bad idea to enable it, but I observe that it is possible for
> > hypervisor to expose a standard transitional device on top of this MMR
> > capability. Thus it will not be known whether guest driver accesses legacy or
> > modern BAR until guest runs.
> > I propose, instead, that device exposes same registers at two addresses and
> > executes reset correctly depending on which address it was accessed through.
> > WDYT?
> Yep, this the exact proposal here.
> Legacy registers exposes via AQ (aka TVQ) or MMR location, behaves like legacy.
> And regular registers at their location as-is.
>
> With that feature bit negotiation is the only thing to relax like worded above.
It's not really different from IO port legacy then.
--
MST
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next prev parent reply other threads:[~2023-04-10 10:20 UTC|newest]
Thread overview: 199+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-30 22:58 [virtio-comment] [PATCH 00/11] Introduce transitional mmr pci device Parav Pandit
2023-03-30 22:58 ` [virtio-comment] [PATCH 01/11] transport-pci: Use lowecase alphabets Parav Pandit
2023-03-30 22:58 ` [virtio-comment] [PATCH 02/11] transport-pci: Move transitional device id to legacy section Parav Pandit
2023-03-31 6:43 ` [virtio-comment] " Michael S. Tsirkin
2023-03-31 21:24 ` [virtio-comment] " Parav Pandit
2023-04-02 7:54 ` [virtio-comment] " Michael S. Tsirkin
2023-04-03 14:42 ` [virtio-comment] " Parav Pandit
2023-04-03 14:50 ` [virtio-comment] " Michael S. Tsirkin
2023-04-03 14:58 ` [virtio-comment] " Parav Pandit
2023-04-03 15:14 ` [virtio-comment] " Michael S. Tsirkin
2023-03-30 22:58 ` [virtio-comment] [PATCH 03/11] transport-pci: Split notes of PCI Device Layout Parav Pandit
2023-03-30 22:58 ` [virtio-comment] [PATCH 04/11] transport-pci: Rename and move legacy PCI Device layout section Parav Pandit
2023-03-30 22:58 ` [virtio-comment] [PATCH 05/11] introduction: Add missing helping verb Parav Pandit
2023-03-30 22:58 ` [virtio-comment] [PATCH 06/11] introduction: Introduce transitional MMR interface Parav Pandit
2023-04-07 9:17 ` [virtio-comment] " Michael S. Tsirkin
2023-03-30 22:58 ` [virtio-comment] [PATCH 07/11] transport-pci: Introduce transitional MMR device id Parav Pandit
2023-04-04 7:28 ` [virtio-comment] " Michael S. Tsirkin
2023-04-04 16:08 ` Parav Pandit
2023-04-07 12:03 ` Michael S. Tsirkin
2023-04-07 15:18 ` Parav Pandit
2023-04-07 15:51 ` Michael S. Tsirkin
2023-04-09 3:15 ` Parav Pandit
2023-04-10 10:18 ` Michael S. Tsirkin [this message]
2023-04-10 14:34 ` Parav Pandit
2023-04-10 19:58 ` Michael S. Tsirkin
2023-04-10 20:16 ` Parav Pandit
2023-04-07 8:37 ` Michael S. Tsirkin
2023-03-30 22:58 ` [virtio-comment] [PATCH 08/11] transport-pci: Introduce virtio extended capability Parav Pandit
2023-04-04 7:35 ` [virtio-comment] " Michael S. Tsirkin
2023-04-04 7:54 ` Cornelia Huck
2023-04-04 12:43 ` Michael S. Tsirkin
2023-04-04 13:19 ` Cornelia Huck
2023-04-04 14:37 ` Michael S. Tsirkin
2023-04-10 16:21 ` Parav Pandit
2023-04-10 19:49 ` Michael S. Tsirkin
2023-04-10 19:57 ` [virtio-comment] " Parav Pandit
2023-04-10 20:02 ` [virtio-comment] " Michael S. Tsirkin
2023-04-11 8:39 ` Cornelia Huck
2023-04-04 21:18 ` [virtio-comment] " Parav Pandit
2023-04-05 5:10 ` [virtio-comment] " Michael S. Tsirkin
2023-04-05 13:16 ` [virtio-comment] " Parav Pandit
2023-04-07 8:15 ` [virtio-comment] " Michael S. Tsirkin
2023-04-10 1:36 ` [virtio-comment] Re: [virtio-dev] " Jason Wang
2023-04-10 6:24 ` Michael S. Tsirkin
2023-04-10 7:16 ` Jason Wang
2023-04-10 10:04 ` Michael S. Tsirkin
2023-04-11 2:19 ` Jason Wang
2023-04-11 7:00 ` Michael S. Tsirkin
2023-04-11 9:07 ` Jason Wang
2023-04-11 10:43 ` Michael S. Tsirkin
2023-04-11 13:59 ` [virtio-comment] " Parav Pandit
2023-04-11 14:11 ` [virtio-comment] " Michael S. Tsirkin
2023-04-11 13:47 ` Parav Pandit
2023-04-11 14:02 ` Michael S. Tsirkin
2023-04-11 14:07 ` Parav Pandit
2023-04-11 14:10 ` Michael S. Tsirkin
2023-04-11 14:30 ` Parav Pandit
2023-04-10 17:54 ` Parav Pandit
2023-04-10 17:58 ` Parav Pandit
2023-04-11 3:28 ` Jason Wang
2023-04-11 19:01 ` [virtio-comment] " Parav Pandit
2023-04-11 21:25 ` [virtio-comment] " Michael S. Tsirkin
2023-04-12 0:40 ` [virtio-comment] " Parav Pandit
2023-04-12 2:56 ` [virtio-comment] " Michael S. Tsirkin
2023-04-12 4:07 ` Jason Wang
2023-04-12 4:20 ` Michael S. Tsirkin
2023-04-12 4:53 ` Jason Wang
2023-04-12 5:25 ` Michael S. Tsirkin
2023-04-12 5:37 ` Jason Wang
2023-04-13 17:03 ` Michael S. Tsirkin
2023-04-12 4:04 ` Jason Wang
2023-04-12 4:13 ` [virtio-comment] " Parav Pandit
2023-04-12 4:20 ` [virtio-comment] " Michael S. Tsirkin
2023-04-12 4:55 ` Jason Wang
2023-05-19 6:10 ` [virtio-comment] " Michael S. Tsirkin
2023-05-19 21:02 ` [virtio-comment] " Parav Pandit
2023-05-21 5:57 ` [virtio-comment] " Michael S. Tsirkin
2023-05-21 13:24 ` [virtio-comment] " Parav Pandit
2023-05-21 14:34 ` [virtio-comment] " Michael S. Tsirkin
2023-03-30 22:58 ` [virtio-comment] [PATCH 09/11] transport-pci: Describe PCI MMR dev config registers Parav Pandit
2023-04-07 8:55 ` [virtio-comment] " Michael S. Tsirkin
2023-04-10 1:33 ` Jason Wang
2023-04-10 6:14 ` Michael S. Tsirkin
2023-04-10 6:20 ` Jason Wang
2023-04-10 6:39 ` Michael S. Tsirkin
2023-04-10 7:20 ` Jason Wang
2023-04-10 10:06 ` Michael S. Tsirkin
2023-04-11 2:13 ` Jason Wang
2023-04-11 7:04 ` Michael S. Tsirkin
2023-04-11 9:01 ` Jason Wang
[not found] ` <CALBs2cXURMEzCGnULicXbsBfwnKE5cZOz=M-_hhFCXZ=Lqb9Nw@mail.gmail.com>
2023-04-11 10:39 ` Michael S. Tsirkin
2023-04-11 10:42 ` Michael S. Tsirkin
2023-04-12 3:58 ` Jason Wang
2023-04-12 4:15 ` Michael S. Tsirkin
2023-04-12 4:51 ` Jason Wang
2023-04-12 5:01 ` Parav Pandit
2023-04-12 5:14 ` Jason Wang
2023-04-12 5:30 ` Parav Pandit
2023-04-12 5:38 ` Jason Wang
2023-04-12 5:55 ` Parav Pandit
2023-04-12 6:15 ` Jason Wang
2023-04-12 14:23 ` Parav Pandit
2023-04-13 1:48 ` Jason Wang
2023-04-13 3:31 ` Parav Pandit
2023-04-13 5:14 ` Jason Wang
2023-04-13 17:19 ` Michael S. Tsirkin
2023-04-13 19:39 ` Parav Pandit
2023-04-14 3:09 ` Jason Wang
2023-04-14 3:18 ` Parav Pandit
2023-04-14 3:37 ` Jason Wang
2023-04-14 3:51 ` Parav Pandit
2023-04-14 7:05 ` Michael S. Tsirkin
2023-04-17 3:22 ` Jason Wang
2023-04-17 17:23 ` Parav Pandit
2023-04-17 20:26 ` Michael S. Tsirkin
2023-04-17 20:28 ` Parav Pandit
2023-04-18 0:36 ` Jason Wang
2023-04-18 1:30 ` Parav Pandit
2023-04-18 11:58 ` Michael S. Tsirkin
2023-04-18 12:09 ` Parav Pandit
2023-04-18 12:30 ` Michael S. Tsirkin
2023-04-18 12:36 ` Parav Pandit
2023-04-18 1:01 ` Jason Wang
2023-04-18 1:48 ` Parav Pandit
2023-04-13 17:24 ` Parav Pandit
2023-04-13 21:02 ` Michael S. Tsirkin
2023-04-13 21:08 ` Parav Pandit
2023-04-14 2:36 ` Jason Wang
2023-04-14 2:43 ` Parav Pandit
2023-04-14 6:57 ` Michael S. Tsirkin
2023-04-16 13:41 ` Parav Pandit
2023-04-16 20:44 ` Michael S. Tsirkin
2023-04-17 16:59 ` Parav Pandit
2023-04-18 1:09 ` Jason Wang
2023-04-18 1:37 ` Parav Pandit
2023-04-14 6:58 ` Michael S. Tsirkin
2023-04-14 3:08 ` Jason Wang
2023-04-14 3:13 ` Parav Pandit
2023-04-14 3:18 ` Jason Wang
2023-04-14 3:22 ` Parav Pandit
2023-04-14 3:29 ` Jason Wang
2023-04-11 13:57 ` Parav Pandit
2023-04-12 4:33 ` Michael S. Tsirkin
2023-03-30 22:58 ` [virtio-comment] [PATCH 10/11] transport-pci: Use driver notification PCI capability Parav Pandit
2023-04-12 4:31 ` [virtio-comment] " Michael S. Tsirkin
2023-04-12 4:37 ` [virtio-comment] " Parav Pandit
2023-04-12 4:43 ` [virtio-comment] " Michael S. Tsirkin
2023-04-12 4:48 ` [virtio-comment] " Parav Pandit
2023-04-12 5:02 ` [virtio-comment] " Michael S. Tsirkin
2023-04-12 5:06 ` Parav Pandit
2023-04-12 5:17 ` Michael S. Tsirkin
2023-04-12 5:24 ` Parav Pandit
2023-04-12 5:27 ` Michael S. Tsirkin
2023-03-30 22:58 ` [virtio-comment] [PATCH 11/11] conformance: Add transitional MMR interface conformance Parav Pandit
2023-03-31 7:03 ` [virtio-comment] Re: [PATCH 00/11] Introduce transitional mmr pci device Michael S. Tsirkin
2023-03-31 21:43 ` Parav Pandit
2023-04-03 14:53 ` Michael S. Tsirkin
2023-04-03 14:57 ` [virtio-comment] " Parav Pandit
2023-04-03 15:06 ` [virtio-comment] " Michael S. Tsirkin
2023-04-03 15:16 ` [virtio-comment] " Parav Pandit
2023-04-03 15:23 ` [virtio-comment] " Michael S. Tsirkin
2023-04-03 15:34 ` Michael S. Tsirkin
2023-04-03 15:47 ` [virtio-comment] " Parav Pandit
2023-04-03 17:28 ` [virtio-comment] " Michael S. Tsirkin
2023-04-03 17:35 ` Parav Pandit
2023-04-03 17:39 ` Michael S. Tsirkin
2023-04-03 15:36 ` Parav Pandit
2023-04-03 17:16 ` Michael S. Tsirkin
2023-04-03 17:29 ` Parav Pandit
2023-04-03 18:02 ` Michael S. Tsirkin
2023-04-03 20:25 ` Parav Pandit
2023-04-03 21:04 ` Michael S. Tsirkin
2023-04-03 22:00 ` Parav Pandit
2023-04-07 9:35 ` Michael S. Tsirkin
2023-04-10 1:52 ` Jason Wang
2023-04-03 14:45 ` [virtio-comment] " Stefan Hajnoczi
2023-04-03 14:53 ` Parav Pandit
2023-04-03 17:48 ` Michael S. Tsirkin
2023-04-03 19:11 ` Stefan Hajnoczi
2023-04-03 20:03 ` Michael S. Tsirkin
2023-04-03 19:48 ` Parav Pandit
2023-04-03 20:02 ` Michael S. Tsirkin
2023-04-03 20:42 ` Parav Pandit
2023-04-03 21:14 ` Michael S. Tsirkin
2023-04-03 22:08 ` Parav Pandit
2023-04-03 19:10 ` Stefan Hajnoczi
2023-04-03 20:27 ` Parav Pandit
2023-04-04 14:30 ` Stefan Hajnoczi
2023-04-12 4:48 ` [virtio-comment] " Michael S. Tsirkin
2023-04-12 4:52 ` [virtio-comment] " Parav Pandit
2023-04-12 5:12 ` [virtio-comment] " Michael S. Tsirkin
2023-04-12 5:15 ` Parav Pandit
2023-04-12 5:23 ` Michael S. Tsirkin
2023-04-12 5:39 ` Parav Pandit
2023-04-12 6:02 ` Parav Pandit
2023-04-12 5:10 ` [virtio-comment] Re: [virtio-dev] " Halil Pasic
2023-04-25 2:42 ` [virtio-comment] " Parav Pandit
2023-05-02 7:17 ` David Edmondson
2023-05-02 13:54 ` Parav Pandit
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