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Re: [PATCH v6 5/7] xen/arm: do not map IRQs and memory for disabled devices
- To: Oleksandr Andrushchenko <andr2000@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Julien Grall <julien@xxxxxxx>
- Date: Tue, 16 Nov 2021 19:22:56 +0000
- Cc: sstabellini@xxxxxxxxxx, oleksandr_tyshchenko@xxxxxxxx, volodymyr_babchuk@xxxxxxxx, Artem_Mygaiev@xxxxxxxx, roger.pau@xxxxxxxxxx, jbeulich@xxxxxxxx, andrew.cooper3@xxxxxxxxxx, george.dunlap@xxxxxxxxxx, paul@xxxxxxx, bertrand.marquis@xxxxxxx, rahul.singh@xxxxxxx, Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
- Delivery-date: Tue, 16 Nov 2021 19:23:10 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi Oleksandr,
On 05/11/2021 06:33, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
Currently Xen maps all IRQs and memory ranges for all devices except
those marked for passthrough, e.g. it doesn't pay attention to the
"status" property of the node.
According to the device tree specification [1]:
- "okay" Indicates the device is operational.
- "disabled" Indicates that the device is not presently operational,
but it might become operational in the future (for example,
something is not plugged in, or switched off).
Refer to the device binding for details on what disabled means
for a given device.
So, "disabled" status is device dependent and mapping should be taken by
case-by-case approach with that respect. Although in general Xen should map
IRQs and memory ranges as the disabled devices might become operational
Right, this change effectively prevent dom0 to use such device if it
becomes operational in the future. So this sounds like a big regression.
How do you plan to handle it?
it
makes it impossible for the other devices, which are not operational in
any case, to skip the mappings.
You wrote "makes it impossible for the other devices", but it is not
clear to me what's would go wrong when we map a disabled device (Dom0
should not touch it). Do you have an example?
Cheers,
--
Julien Grall
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