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Re: Xen 4.18 pvshim console issue (with patch)
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Wed, 18 Oct 2023 11:24:56 +0000
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- Cc: Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 18 Oct 2023 11:25:17 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: Xen 4.18 pvshim console issue (with patch)
Hi Andrew,
> On Oct 18, 2023, at 19:23, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>
> On 18/10/2023 12:20 pm, Manuel Bouyer wrote:
>> On Wed, Oct 18, 2023 at 11:44:22AM +0100, Andrew Cooper wrote:
>>> On 18/10/2023 11:38 am, Manuel Bouyer wrote:
>>>> Hello,
>>>> With Xen 4.18, a PV domain running under pvshim doesn't get console input.
>>>> This is because the domain id in pvshim isn't 0 (and on x86 max_init_domid
>>>> is
>>>> hardwired to 0), so console_input_domain() will never select that domain
>>>> as input.
>>>>
>>>> The attached patch fixes it by translating 0 to the real domain id for
>>>> pvshim, but there may be a better way to do this.
>>>>
>>> Thankyou for the report.
>>>
>>> First, CC'ing Henry as 4.18 release manager.
>>>
>>> There have been changes in how this works recently in 4.18, notably c/s
>>> c2581c58bec96.
>> Yes, it looks like this one introduced the problem.
>> Before this, we would switch console_rx to 1 without checking if
>> domain (console_rx - 1) exists, and console_rx == 1 is a special case
>> in __serial_rx()
>>
>>> However, it's not obvious whether this worked in 4.17 or not. i.e.
>>> whether it's a regression in 4.18, or whether it's been broken since PV
>>> Shim was introduced.
>> I don't know for 4.16 or 4.17 but I can tell that it's working in 4.15
>>
>
> That commit is new in 4.18, so Henry - this is a release
> critical/blocker owing to it being a regression vs 4.17.
Noted down.
Out of curiosity, do we have maintainers for that specific driver? It would
be good to looping them in.
Kind regards,
Henry
>
> I'll try and put some brainpower towards it when I get some other 4.18
> work sorted.
>
> ~Andrew
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