RE: [Xen-ia64-devel] RFC: ptc.ga implementation for SMP-g

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>From: Xu,Anthony
>Sent: 2006年4月4日 22:47
>The control flow is as below
>1. vcpu1 emulates ptc.ga
>2. vcpu1 executes vhpt_flush_address to purge current LP VHPT,
>  and executes ptc.l to purge machine TLB on current LPs.
>3. vcpu1 creates a structure which describe this ptc.ga, including virtual
>  address, address range and rid, and connect this structure to vcpu2.
>4. then vcpu1 sets a flag in vcpu2, indicating there is ptc.ga executed on
>   this VMM.
>5. When vcpu2 traps into hypervisor, hypervisor will check whether this
>  flag is set, if yes, vcpu2 will execute vhpt_flush_address and ptc.l.
>
>There is a time window between purges of vcpu1 and vcpu2, I'm not sure
>whether it is workable.
>

That actually gives you worse performance than IPI, because vcpu1 has 
to wait unpredicted period for vcpu2 to complete the purge operation. 
Consider other vcpus may be in runqueue, maybe in block state...

Thanks,
Kevin

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