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Re: [Qemu-ppc] [Qemu-devel] [PATCH 0/4] QOM'ify work for ppc

From: 赵小强
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH 0/4] QOM'ify work for ppc
Date: Thu, 5 Jan 2017 08:53:07 +0800


Just one more comment:
After check the code flow, It's clear that the initialized memory region must 
be add to address space by calling memory_region_add_subregion in platform code 
before it can be accessed.

Best wishes !

> 在 2017年1月5日,08:20,David Gibson <address@hidden> 写道:
>> On Wed, Jan 04, 2017 at 05:04:02PM +0000, Peter Maydell wrote:
>>> On 4 January 2017 at 03:28, David Gibson <address@hidden> wrote:
>>>> On Tue, Jan 03, 2017 at 10:02:21PM +0800, 赵小强 wrote:
>>>> Hi,david:
>>>>   To my understanding,what must be put in the realize function  is
>>>>   code which depends on property values. What's the benefit of
>>>>   moving memory region initialization into realize function?  I can
>>>>   not figure out, can you make some explanations?
>>> If nothing else it's better in realize() for consistency with other
>>> devices.
>> I'm not sure we're terribly consistent at all, really. My understanding
>> was about the same as 赵小强 -- put stuff in init unless it has to
>> go in realize because it depends on properties or might fail or
>> has permanent effects on the simulation.
>> Lots of existing devices do memory_region_init* calls in
>> their init functions.
>> We should probably write down our preferences somewhere, perhaps
>> http://wiki.qemu.org/Documentation/QOMConventions
>>> I'm not familiar enough with the details to be sure, but I also think
>>> it's not safe in instance_init.  Once memory regions are registered,
>>> the device can potentially interact with other devices in the virtual
>>> machine.  realize() is sequenced to expect that, instance_init is not.
>> Hmm, that doesn't sound right to me. The other devices will only
>> interact with the memory regions when the calling code has
>> finished doing the create/realize/map memory regions sequence --
>> an MR on its own doesn't do anything unless somebody maps it into
>> an address space.
> Huh.  Ok, I guess I was wrong.
> Alright, 赵小强, feel free to repost addressing just the other
> comments and I'll merge.
> -- 
> David Gibson            | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au    | minimalist, thank you.  NOT _the_ _other_
>                | _way_ _around_!
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