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Re: [Qemu-devel] [PATCH qemu v3 01/13] memory: Postpone flatview and dis


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH qemu v3 01/13] memory: Postpone flatview and dispatch tree building till all devices are added
Date: Tue, 19 Sep 2017 16:23:13 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 19/09/2017 16:12, Alexey Kardashevskiy wrote:
>>> What is the exact concern about the "[PATCH qemu v3 01/13] memory: Postpone
>>> flatview and dispatch tree building till all devices are added"? Is it that
>>> you missed that modern AS thing in virtio and thought we can do well even
>>> without it?
>> I am afraid that some of the special sysbus devices (not PCI, those go
>> through the bus master DMA region and it's empty on startup) might write
>> to memory during initialization.
> 
> And somehow QEMU guarantees that all RAM MRs are rendered to FlatViews even
> though some might be added via -device (can they btw?)?

I don't know, but as discussed on IRC, I think this is a pretty
different change from the rest of the series---which should have zero
change except for going faster---so I'd prefer to keep it out for now
and see where optimization can get us.

Paolo



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