Re: [Qemu-devel] [PATCH 11/12] kvm: x86: Pass KVMState to kvm_arch_get_supported_cpuid

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-06-09 20:08, Eduardo Habkost wrote:
> On Thu, Jun 09, 2011 at 07:41:03PM +0200, Jan Kiszka wrote:
> <snip>
>>> I'm wondering if it wouldn't be simpler to keep the existing interface
>>> but just initialize CPUState->kvm_state earlier (today it is initialized
>>> only on kvm_init_vcpu(), although the kvm_state global is initialized
>>> much earlier).
>>
>> If there was more need for a slit up, I would agree. But I do not see it.
> 
> I guess it won't hurt to make the functions require only what they
> really need.

Yes, so this patch has an independent value IMO.

> 
>>>
>>> Even with this new KVMState-based interface, code that needs to use
>>> these functions before kvm_init_vcpu() (e.g.
>>> check_features_against_host()) will have to use the 'kvm_state' global
>>> (and I would like to avoid that).
>>
>> That is a different topic that needs to be resolved for other use cases
>> as well (e.g. for kvm devices). In many cases you should be able to find
>> a way to pass kvm_state from functions that already holds a reference.
>> Is that not true for your use case?
> 
> My use case is cpu_x86_register()/check_features_against_host(), that
> hold only a CPUState reference, and I wouldn't like to add a new
> reference to the kvm_state global variable there.

For me, this is like requiring kvm_state for kvm_check_extension, and I
wouldn't hesitate using the global state until we solved that in a
better way. But if you feel like it's not appropriate here, then let's
go for early/late vcpu init.

Jan


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