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Re: [PATCH v5 01/11] xen/arm: xc_domain_ioport_permission(..) not supported on ARM.
- To: Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 12 Oct 2021 12:20:34 +0200
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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>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Tue, 12 Oct 2021 10:20:50 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 12.10.2021 12:06, Oleksandr Andrushchenko wrote:
> On 12.10.21 13:01, Jan Beulich wrote:
>> On 12.10.2021 11:38, Oleksandr Andrushchenko wrote:
>>> On 12.10.21 12:32, Jan Beulich wrote:
>>>> The minimal thing I'd suggest (or maybe you're doing this already)
>>>> would be to expose such BARs to the guest as r/o zero, rather than
>>>> letting their port nature "shine through".
>>> If we have the same, but baremetal then which entity disallows
>>> those BARs to shine?
>> I'm sorry, but I don't understand what you're trying to say.
>>
>>> I mean that if guest wants to crash... why
>>> should we stop it and try emulating something special for it?
>> This isn't about a guest "wanting to crash", but a driver potentially
>> getting mislead into thinking that it can driver a device a certain
>> way.
> Well, for the guest, as we do not advertise IO in the emulated host
> bridge, the driver won't be able to allocate any IO at all. Thus, even
> if we have a BAR with PCI_BASE_ADDRESS_SPACE_IO bit set, the
> driver won't get anything. So, I think this is equivalent to a baremetal
> use-case where we have no IO supported by the host bridge and
> a device with IO BAR.
Oh, now I follow. Fair enough.
Jan
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