[Qemu-devel] Re: [kvm-devel] [PATCH][UPDATE] kvm-userspace: sync icache for morearchitectures

[Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>]

Hollis Blanchard wrote:
> On Fri, 2007-12-14 at 10:07 +0100, Christian Ehrhardt wrote:
>> Hollis Blanchard wrote:
>>> A comment to explain why the icache needs flushing only in the KVM
>> case
>>> would be useful. Other than that I'm fine with it.
>>>
>>> Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
>> AFAIK Plain qemu does not directly execute guest code on the
>> processor,
>> so the icache is not an issue for it.
>> Qemu itself has the flush_icache_range function only as helper for the
>> dynamic code generation.
>> But we may now write executable guest code with our intercepted mmio
>> handling that is directly executed when switching back to the guest
>> context, therefore we need that invalidation in the kvm case.
>>
>> For the case that I'm overlooking something in plain qemu, so that it
>> might need it too I add qemu-devel@nongnu.org for comments from there,
>> but currently I think to have it in #ifdef USE_KVM is the right way.
>>
>>
>> P.S. Hollis did you mean you would like to see a comment in the code
>> where that call takes place?
> 
> Yes! Hopefully much shorter than this email... :-P
> 
comment added, rebased and resent together with a updated mmio
callback simplification patch - I hope I didn't overlook a response
to the mmio callback thread again this time ;-)

-- 

Grüsse / regards, 
Christian Ehrhardt

IBM Linux Technology Center, Open Virtualization
+49 7031/16-3385
Ehrhardt@linux.vnet.ibm.com
Ehrhardt@de.ibm.com

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