On Thu, Jan 05, 2017 at 08:53:07AM +0800, 赵小强 wrote: > Ok！ > > 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.
Yes.. but I don't see how that's relevant to the discussion at hand. > > Best wishes ！ > > > 在 2017年1月5日，08:20，David Gibson <da...@gibson.dropbear.id.au> 写道： > > > >> On Wed, Jan 04, 2017 at 05:04:02PM +0000, Peter Maydell wrote: > >>> On 4 January 2017 at 03:28, David Gibson <da...@gibson.dropbear.id.au> > >>> 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_! http://www.ozlabs.org/~dgibson
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