From: Bertrand Marquis <Bertrand.Marquis@arm.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>,
Rahul Singh <Rahul.Singh@arm.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Andre Przywara <Andre.Przywara@arm.com>,
Ian Jackson <iwj@xenproject.org>, Wei Liu <wl@xen.org>,
Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>
Subject: Re: [PATCH v5 01/11] xen/arm: xc_domain_ioport_permission(..) not supported on ARM.
Date: Mon, 11 Oct 2021 17:11:31 +0000 [thread overview]
Message-ID: <EB1CB53B-9D5A-49C5-A687-841BF94A153F@arm.com> (raw)
In-Reply-To: <YWRnMfAi808TQ4Gt@MacBook-Air-de-Roger.local>
Hi Roger,
> On 11 Oct 2021, at 17:32, Roger Pau Monné <roger.pau@citrix.com> wrote:
>
> On Mon, Oct 11, 2021 at 02:16:19PM +0000, Bertrand Marquis wrote:
>> Hi Roger,
>>
>>> On 11 Oct 2021, at 14:57, Roger Pau Monné <roger.pau@citrix.com> wrote:
>>>
>>> On Mon, Oct 11, 2021 at 01:40:30PM +0000, Bertrand Marquis wrote:
>>>> Hi Roger,
>>>>
>>>> + Oleksandr to have a better PCI expert then me.
>>>>
>>>>> On 11 Oct 2021, at 14:20, Roger Pau Monné <roger.pau@citrix.com> wrote:
>>>>>
>>>>> On Mon, Oct 11, 2021 at 12:11:04PM +0000, Bertrand Marquis wrote:
>>>>>> Hi Roger,
>>>>>>
>>>>>>> On 11 Oct 2021, at 12:47, Roger Pau Monné <roger.pau@citrix.com> wrote:
>>>>>>>
>>>>>>> On Wed, Oct 06, 2021 at 06:40:27PM +0100, Rahul Singh wrote:
>>>>>>>> ARM architecture does not implement I/O ports. Ignore this call on ARM
>>>>>>>> to avoid the overhead of making a hypercall just for Xen to return
>>>>>>>> -ENOSYS.
>>>>>>>
>>>>>>> What is the cal trace of this function actually on Arm?
>>>>>>>
>>>>>>> AFAICT libxl will only call xc_domain_ioport_permission if there are
>>>>>>> IO ports explicitly defined in the guest configuration, or if any of
>>>>>>> the BARs of the PCI device is in the IO space, which is not possible
>>>>>>> on Arm.
>>>>>>
>>>>>> PCI devices BARs can be in the IO space as the PCI devices are not
>>>>>> Arm specific. There is not ioports on arm so to be used those can be
>>>>>> in some cases remapped and accessed as MMIOs or are not possible
>>>>>> to use at all.
>>>>>>
>>>>>> But the IO space does appear when BARs are listed even on Arm.
>>>>>
>>>>> Urg, I wonder whether those devices with IO BARs will work correctly
>>>>> under Arm then.
>>>>>
>>>>> How do you know whether the BAR has been remapped from IO space into
>>>>> MMIO?
>>>>
>>>> We cannot, I think the platform will define if this is the case and where.
>>>> @oleksandr: I remember that this was discussed during some of our
>>>> meetings but I have no idea of the details here, can you help ?
>>>>
>>>>>
>>>>> IMO instead of faking a successful return value from
>>>>> xc_domain_ioport_permission we should avoid the call completely in the
>>>>> first place, specially if we need to instead issue a call to
>>>>> xc_domain_iomem_permission.
>>>>
>>>> At the end we will never have to issue this because this will never be a matter
>>>> of “iomem” permission as there would not be any way to cut on something under
>>>> the page. If this is to be supported one day, it will probably have to be fully emulated
>>>> to keep the isolation.
>>>
>>> So you have a set of memory pages that map accesses from
>>> MMIO into IO space but it's not possible to isolate specific IO port
>>> regions as they are all contiguous in the same page(s).
>>
>> Exact.
>>
>>>
>>>> Right now on arm you can just make the more simple assumption that ioports are
>>>> just not supported.
>>>
>>> Would it make sense in the future to provide a memory region to guests
>>> in order to use for IO port accesses, and call
>>> xc_domain_ioport_permission to set which ports would be allowed?
>>
>> Right now we do not plan to support this at all and we will have to
>> figure this out if we do this one day.
>>
>>>
>>> I think the commit message needs to at least be expanded in order to
>>> contain the information provided here. It might also be helpful to
>>> figure out whether we would have to handle IO port accesses in the
>>> future on Arm, or if it's fine to just ignore them.
>>
>> All our investigations and tests have been done without supporting it
>> without any issues so this is not a critical feature (most devices can
>> be operated without using the I/O ports).
>
> IMO we should let the users know they attempted to use a device with
> BARs in the IO space, and that those BARs won't be accessible which
> could make the device not function as expected.
>
> Do you think it would be reasonable to attempt the hypercall on Arm
> also, and in case of error (on Arm) just print a warning message and
> continue operations as normal?
I think this would lead to a warning printed on lots of devices where in
fact there would be no issues.
If this is an issue for a device driver because it cannot operate without
I/O ports, this will be raised by the driver inside the guest.
So in the current state I think the way to do it is right.
Regards
Bertrand
>
> Thanks, Roger.
next prev parent reply other threads:[~2021-10-11 17:13 UTC|newest]
Thread overview: 190+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-06 17:40 [PATCH v5 00/11] PCI devices passthrough on Arm Rahul Singh
2021-10-06 17:40 ` [PATCH v5 01/11] xen/arm: xc_domain_ioport_permission(..) not supported on ARM Rahul Singh
2021-10-11 11:47 ` Roger Pau Monné
2021-10-11 12:11 ` Bertrand Marquis
2021-10-11 13:20 ` Roger Pau Monné
2021-10-11 13:40 ` Bertrand Marquis
2021-10-11 13:57 ` Roger Pau Monné
2021-10-11 14:16 ` Bertrand Marquis
2021-10-11 16:32 ` Roger Pau Monné
2021-10-11 17:11 ` Bertrand Marquis [this message]
2021-10-12 8:29 ` Jan Beulich
2021-10-12 8:41 ` Bertrand Marquis
2021-10-12 9:32 ` Jan Beulich
2021-10-12 9:38 ` Oleksandr Andrushchenko
2021-10-12 10:01 ` Jan Beulich
2021-10-12 10:06 ` Oleksandr Andrushchenko
2021-10-12 10:20 ` Jan Beulich
2021-10-12 10:41 ` Bertrand Marquis
2021-10-12 10:44 ` Jan Beulich
2021-10-12 14:53 ` Ian Jackson
2021-10-12 16:15 ` Bertrand Marquis
2021-10-12 16:29 ` Ian Jackson
2021-10-12 20:42 ` Stefano Stabellini
2021-10-13 8:07 ` Roger Pau Monné
2021-10-13 11:52 ` Ian Jackson
2021-10-13 8:02 ` Roger Pau Monné
2021-10-13 12:02 ` Ian Jackson
2021-10-12 9:40 ` Bertrand Marquis
2021-10-12 10:03 ` Jan Beulich
2021-10-11 14:16 ` Oleksandr Andrushchenko
2021-10-06 17:40 ` [PATCH v5 02/11] xen/arm: Add PHYSDEVOP_pci_device_(*add/remove) support for ARM Rahul Singh
2021-10-07 0:05 ` Stefano Stabellini
2021-10-07 12:58 ` Jan Beulich
2021-10-21 9:28 ` xen/arm: Missing appropriate locking for the IOMMU (WAS Re: [PATCH v5 02/11] xen/arm: Add PHYSDEVOP_pci_device_(*add/remove) support for ARM) Julien Grall
2021-10-21 13:15 ` Bertrand Marquis
2021-10-21 13:47 ` Julien Grall
2021-10-21 13:52 ` Bertrand Marquis
2021-10-06 17:40 ` [PATCH v5 03/11] xen/arm: Add cmdline boot option "pci-passthrough = <boolean>" Rahul Singh
2021-10-07 8:27 ` Jan Beulich
2021-10-07 8:32 ` Rahul Singh
2021-10-07 12:59 ` Jan Beulich
2021-10-06 17:40 ` [PATCH v5 04/11] xen/arm: PCI host bridge discovery within XEN on ARM Rahul Singh
2021-10-06 17:40 ` [PATCH v5 05/11] xen/arm: Add support for Xilinx ZynqMP PCI host controller Rahul Singh
2021-10-06 17:40 ` [PATCH v5 06/11] xen/arm: Implement pci access functions Rahul Singh
2021-10-06 17:40 ` [PATCH v5 07/11] xen/domctl: Introduce XEN_DOMCTL_CDF_vpci flag Rahul Singh
2021-10-07 13:08 ` Jan Beulich
2021-10-08 18:06 ` Andrew Cooper
2021-10-08 21:12 ` Julien Grall
2021-10-08 21:46 ` Stefano Stabellini
2021-10-11 9:24 ` Julien Grall
2021-10-11 11:29 ` Michal Orzel
2021-10-11 11:35 ` Jan Beulich
2021-10-11 13:17 ` Roger Pau Monné
2021-10-11 9:48 ` Ian Jackson
2021-10-11 9:27 ` Roger Pau Monné
2021-10-11 12:06 ` Michal Orzel
2021-10-12 10:38 ` Michal Orzel
2021-10-13 8:30 ` Roger Pau Monné
2021-10-13 9:36 ` Bertrand Marquis
2021-10-13 10:56 ` Roger Pau Monné
2021-10-13 12:11 ` Bertrand Marquis
2021-10-13 12:57 ` Jan Beulich
2021-10-13 20:41 ` Stefano Stabellini
2021-10-14 6:23 ` Jan Beulich
2021-10-14 7:53 ` Bertrand Marquis
2021-10-13 14:28 ` Roger Pau Monné
2021-10-13 20:53 ` Stefano Stabellini
2021-10-13 23:21 ` Stefano Stabellini
2021-10-12 21:48 ` Stefano Stabellini
2021-10-13 6:18 ` Jan Beulich
2021-10-13 7:11 ` Michal Orzel
2021-10-06 17:40 ` [PATCH v5 08/11] xen/arm: Enable the existing x86 virtual PCI support for ARM Rahul Singh
2021-10-07 13:43 ` Jan Beulich
2021-10-11 12:41 ` Bertrand Marquis
2021-10-11 13:09 ` Jan Beulich
2021-10-11 13:34 ` Bertrand Marquis
2021-10-11 14:10 ` Jan Beulich
2021-10-11 14:52 ` Bertrand Marquis
2021-10-11 18:18 ` Stefano Stabellini
2021-10-12 8:04 ` Jan Beulich
2021-10-12 21:37 ` Stefano Stabellini
2021-10-13 6:10 ` Jan Beulich
2021-10-13 10:02 ` Bertrand Marquis
2021-10-13 12:21 ` Jan Beulich
2021-10-12 15:04 ` Julien Grall
2021-10-12 16:12 ` Bertrand Marquis
2021-10-12 16:20 ` Julien Grall
2021-10-12 17:50 ` Bertrand Marquis
2021-10-11 10:51 ` Roger Pau Monné
2021-10-11 16:12 ` Bertrand Marquis
2021-10-11 16:20 ` Oleksandr Andrushchenko
2021-10-11 16:43 ` Roger Pau Monné
2021-10-11 17:15 ` Bertrand Marquis
2021-10-11 18:30 ` Oleksandr Andrushchenko
2021-10-11 19:27 ` Stefano Stabellini
2021-10-12 5:34 ` Oleksandr Andrushchenko
2021-10-12 7:44 ` Bertrand Marquis
2021-10-12 14:32 ` Julien Grall
2021-10-12 14:34 ` Bertrand Marquis
2021-10-13 8:45 ` Roger Pau Monné
2021-10-13 9:48 ` Bertrand Marquis
2021-10-13 10:33 ` Roger Pau Monné
2021-10-13 13:00 ` Jan Beulich
2021-10-13 14:51 ` Oleksandr Andrushchenko
2021-10-13 15:15 ` Jan Beulich
2021-10-13 19:27 ` Stefano Stabellini
2021-10-14 6:33 ` Jan Beulich
2021-10-14 7:53 ` Bertrand Marquis
2021-10-14 9:03 ` Bertrand Marquis
2021-10-14 9:24 ` Jan Beulich
2021-10-06 17:40 ` [PATCH v5 09/11] xen/arm: Transitional change to build HAS_VPCI on ARM Rahul Singh
2021-10-11 11:43 ` Roger Pau Monné
2021-10-11 12:15 ` Bertrand Marquis
2021-10-12 1:32 ` Stefano Stabellini
2021-10-06 17:40 ` [PATCH v5 10/11] arm/libxl: Emulated PCI device tree node in libxl Rahul Singh
2021-10-06 18:01 ` Julien Grall
2021-10-07 0:26 ` Stefano Stabellini
2021-10-07 15:31 ` Rahul Singh
2021-10-07 10:53 ` Ian Jackson
2021-10-07 15:29 ` Rahul Singh
2021-10-07 16:11 ` Ian Jackson
2021-10-11 13:46 ` Roger Pau Monné
2021-10-14 17:16 ` Bertrand Marquis
2021-10-14 14:49 ` [PATCH v6 0/3] PCI devices passthrough on Arm Bertrand Marquis
2021-10-14 14:49 ` [PATCH v6 1/3] xen/vpci: Move ecam access functions to common code Bertrand Marquis
2021-10-14 16:06 ` Jan Beulich
2021-10-14 17:09 ` Bertrand Marquis
2021-10-15 6:29 ` Jan Beulich
2021-10-15 7:37 ` Bertrand Marquis
2021-10-15 8:13 ` Jan Beulich
2021-10-15 8:20 ` Bertrand Marquis
2021-10-15 8:24 ` Jan Beulich
2021-10-15 9:49 ` Roger Pau Monné
2021-10-14 23:47 ` Stefano Stabellini
2021-10-15 7:44 ` Roger Pau Monné
2021-10-15 7:53 ` Bertrand Marquis
2021-10-15 9:53 ` Roger Pau Monné
2021-10-15 10:12 ` Bertrand Marquis
2021-10-15 10:14 ` Jan Beulich
2021-10-14 14:49 ` [PATCH v6 2/3] xen/arm: Enable the existing x86 virtual PCI support for ARM Bertrand Marquis
2021-10-14 23:49 ` Stefano Stabellini
2021-10-15 6:40 ` Jan Beulich
2021-10-15 9:59 ` Ian Jackson
2021-10-15 10:10 ` Bertrand Marquis
2021-10-15 8:00 ` Jan Beulich
2021-10-15 10:09 ` Bertrand Marquis
2021-10-15 10:14 ` Ian Jackson
2021-10-15 10:18 ` Jan Beulich
2021-10-15 11:35 ` Roger Pau Monné
2021-10-15 12:13 ` Bertrand Marquis
2021-10-15 12:18 ` Jan Beulich
2021-10-15 12:28 ` Bertrand Marquis
2021-10-15 13:00 ` Jan Beulich
2021-10-15 13:10 ` Bertrand Marquis
2021-10-15 10:38 ` Jan Beulich
2021-10-15 8:32 ` Roger Pau Monné
2021-10-15 8:42 ` Michal Orzel
2021-10-15 9:52 ` Bertrand Marquis
2021-10-15 10:13 ` Luca Fancellu
2021-10-15 10:17 ` Bertrand Marquis
2021-10-15 10:19 ` Roger Pau Monné
2021-10-15 10:31 ` Bertrand Marquis
2021-10-15 10:24 ` Jan Beulich
2021-10-15 10:33 ` Bertrand Marquis
2021-10-15 10:41 ` Jan Beulich
2021-10-15 10:48 ` Bertrand Marquis
2021-10-15 10:51 ` Jan Beulich
2021-10-15 11:08 ` Bertrand Marquis
2021-10-15 13:47 ` Roger Pau Monné
2021-10-15 14:00 ` Luca Fancellu
2021-10-15 14:32 ` Roger Pau Monné
2021-10-14 14:49 ` [PATCH v6 3/3] arm/libxl: Emulated PCI device tree node in libxl Bertrand Marquis
2021-10-14 17:54 ` [PATCH v6 3/3] arm/libxl: Emulated PCI device tree node in libxl [and 1 more messages] Ian Jackson
2021-10-14 23:50 ` Stefano Stabellini
2021-10-15 7:28 ` Julien Grall
2021-10-15 7:41 ` Michal Orzel
2021-10-15 9:01 ` Julien Grall
2021-10-15 10:02 ` Ian Jackson
2021-10-15 10:58 ` Michal Orzel
2021-10-15 11:04 ` Michal Orzel
2021-10-15 11:46 ` Ian Jackson
2021-10-15 11:53 ` Michal Orzel
2021-10-15 12:10 ` Julien Grall
2021-10-15 12:14 ` Ian Jackson
2021-10-15 12:13 ` Ian Jackson
2021-10-12 15:03 ` [PATCH v5 10/11] arm/libxl: Emulated PCI device tree node in libxl Ian Jackson
2021-10-06 17:40 ` [PATCH v5 11/11] xen/arm: Add linux,pci-domain property for hwdom if not available Rahul Singh
2021-10-13 20:54 ` Stefano Stabellini
2021-10-07 19:54 ` [PATCH v5 00/11] PCI devices passthrough on Arm Stefano Stabellini
2021-10-07 21:29 ` Rahul Singh
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=EB1CB53B-9D5A-49C5-A687-841BF94A153F@arm.com \
--to=bertrand.marquis@arm.com \
--cc=Andre.Przywara@arm.com \
--cc=Oleksandr_Andrushchenko@epam.com \
--cc=Rahul.Singh@arm.com \
--cc=iwj@xenproject.org \
--cc=jgross@suse.com \
--cc=roger.pau@citrix.com \
--cc=sstabellini@kernel.org \
--cc=wl@xen.org \
--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).