Re: [PATCH 03/10 v2] xen/arm: vpl011: Enable pl011 emulation for a guest domain in Xen

From: "Jan Beulich" <JBeulich@suse.com>
To: Julien Grall <julien.grall@arm.com>,
	Bhupinder Thakur <bhupinder.thakur@linaro.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH 03/10 v2] xen/arm: vpl011: Enable pl011 emulation for a guest domain in Xen
Date: Wed, 03 May 2017 04:47:46 -0600	[thread overview]
Message-ID: <5909D17202000078001564BD@prv-mh.provo.novell.com> (raw)
In-Reply-To: <19e428fc-0417-146b-73f8-80f6b4d9da2d@arm.com>

>>> On 03.05.17 at 12:22, <julien.grall@arm.com> wrote:

> 
> On 02/05/17 16:23, Julien Grall wrote:
>> Hi Bhupinder,
>>
>> On 02/05/17 16:20, Bhupinder Thakur wrote:
>>> Hi Jan,
>>>
>>>>> @@ -631,6 +632,9 @@ int arch_domain_create(struct domain *d,
>>>>> unsigned int domcr_flags,
>>>>>      if ( (rc = domain_vtimer_init(d, config)) != 0 )
>>>>>          goto fail;
>>>>>
>>>>> +    if ( domcr_flags & DOMCRF_vuart )
>>>>> +        if ( (rc = domain_vpl011_init(d, config)) != 0 )
>>>>> +            goto fail;
>>>>>      update_domain_wallclock_time(d);
>>>>
>>> I am planning to remove the usage of domain creation flag to check
>>> whether vuart is enabled/disabled. Please see my next comment. With
>>> that change, domain_vpl011_init() will be called always. The
>>> domain_vpl011_init() will check whether vuart is enabled or disabled
>>> in the config structure passed. If vuart is enabled then it will go
>>> ahead with vpl011 initialization else it will return without
>>> initializing vpl011.
>>
>> Please don't do that. The arch code decides whether domain_vpl011_init
>> not the invert.
> 
> I was wondering whether it would be better to defer the PL011 creation 
> to a domctl. This could be called after the domain is created with all 
> the information required (MMIO region, Console PFN...).
> 
> This would also make the migration support more trivial as the we will 
> not need to know in advance whether a UART is been used.
> 
> Any opinions?

Wasn't that the suggestion given during v1 review?

Jan

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