Re: [XTF 4/4] setup: Setup PV console for HVM guests on xen >4.2

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/04/2020 12:51, Wieczorkiewicz, Pawel wrote:
>> On 16. Apr 2020, at 12:36, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>>
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>>
>>
>> On 16/04/2020 10:41, Pawel Wieczorkiewicz wrote:
>>> @@ -272,9 +274,23 @@ void arch_setup(void)
>>>
>>>     init_hypercalls();
>>>
>>> -    if ( !is_initdomain() )
>>> +    xen_version = hypercall_xen_version(XENVER_version, NULL);
>>> +    if ( version )
>>> +        *version = xen_version;
>>> +
>>> +    /*
>>> +     * The setup_pv_console function registers a writing function
>>> +     * that makes hvm guests crash on Xen 4.2
>> This comment in particular is rather concerning.  Even if there is a
>> configuration issue in 4.2 stopping the PV console from being wired up
>> properly, nothing involved in transmitting on the console should crash
>> the guest.
>>
> I am again a little short on details here. Maybe Paul could chime in.
> But, I vagualy remember it was something about the init_pv_console()’s:
>
>     if ( port >= (sizeof(shared_info.evtchn_pending) * CHAR_BIT) )
>         panic("evtchn %u out of evtchn_pending[] range\n", port);

This is a sanity check about not overrunning the evtchn_pending array. 
However, the check is still correct AFAICT.

port will either be 0 (if not configured by the toolstack), or strictly
less than 8 if configured properly.

What value are you seeing here?

~Andrew