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Re: [PATCH v5 01/11] xen/arm: xc_domain_ioport_permission(..) not supported on ARM.
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Date: Mon, 11 Oct 2021 12:11:04 +0000
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- Cc: Rahul Singh <Rahul.Singh@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andre Przywara <Andre.Przywara@xxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
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- Thread-topic: [PATCH v5 01/11] xen/arm: xc_domain_ioport_permission(..) not supported on ARM.
Hi Roger,
> On 11 Oct 2021, at 12:47, Roger Pau Monné <roger.pau@xxxxxxxxxx> 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.
Regards
Bertrand
>
> Thanks, Roger.
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