Re: [patch] paravirt: VDSO page is essential

[Avi Kivity <avi@qumranet.com>]

Ingo Molnar wrote:
> * Andi Kleen <ak@suse.de> wrote:
>
>   
>> I think we would need to have a paravirt ops callback to decide this 
>> first. But it doesn't look critical to me anyways.
>>     
>
> well, it's critical to me in two ways: 1) to make the i386 paravirt code 
> clean 2) to have a proper VDSO for a KVM paravirtual guest. The original 
> change is also bad because it changes how a Linux guest behaves: it 
> turns off the vdso by default, and disables the compat VDSO. I.e. it's a 
> bad performance step backwards if CONFIG_PARAVIRT is enabled (uses int 
> $0x80 instead of sysenter), which hurts only KVM and basically none of 
> the other hypervisors. It also muddifies the VDSO picture wrt. 
> virtualization.
>
>   

kvm paravirt is only used by developers at this time.  I don't have a 
problem with solving this in the 2.6.22 timeframe.

-- 
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