From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v5] KVM: VMX: Execute WBINVD to keep data consistency
 with assigned devices
Date: Tue, 29 Jun 2010 11:31:06 -0300
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Cc: Sheng Yang <sheng@linux.intel.com>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	Joerg Roedel <joerg.roedel@amd.com>, kvm@vger.kernel.org,
	"Yaozu (Eddie) Dong" <eddie.dong@intel.com>
To: Avi Kivity <avi@redhat.com>
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On Tue, Jun 29, 2010 at 04:50:49PM +0300, Avi Kivity wrote:
> On 06/29/2010 04:35 PM, Marcelo Tosatti wrote:
> >>>
> >>>work_on_cpu() loop instead of smp_call_function_many(), to avoid executing
> >>>wbinvd with interrupts disabled.
> >>Why?  wbinvd is not interruptible.
> >Right. But still, smp_call_function_many() is going to busy-spin until
> >the target CPUs finish their work, while work_on_cpu() will schedule.
> >
> 
> Good point.  So in the worst case we double the hit.
> 
> >Also the IPI request has to handled immediately, bypassing the
> >scheduler.
> 
> We're screwed on that point in any case, once wbinvd starts the
> scheduler is bypassed.
> 
> But work_on_cpu() has its own problems.  It creates a kthread
> (perhaps not too bad).  Maybe queue_work_on()?

queue_work_on + flush_work should be equivalent to work_on_cpu (without 
thread creation).