Re: [Xen-devel] [PATCH v2 1/2] VMX: fix VMCS race on context-switch paths

[Dario Faggioli <raistlin@xxxxxxxx>]

On Thu, 2017-11-09 at 03:17 -0700, Jan Beulich wrote:
> > > > On 09.11.17 at 10:54, <raistlin@xxxxxxxx> wrote:
> > On Tue, 2017-11-07 at 14:24 +0000, Igor Druzhinin wrote:
> > > Perhaps I should improve my diagram:
> > > 
> > > pCPU1: vCPUx of domain X -> migrate to pCPU2 -> switch to idle
> > > context
> > > -> RCU callbacks -> vcpu_destroy(vCPUy of domain Y) ->
> > > vmx_vcpu_disable_pml() -> vmx_vmcs_clear() (VMCS is trashed at
> > > this
> > > point on pCPU1)
> > > 
> > > pCPU2: context switch into vCPUx -> vCPUx.is_running = 1 -> TLB
> > > flush
> > > from context switch to clean TLB on pCPU1
> > 
> > But, more important, how come you are context switching to
> > something
> > that has is_running == 1 ? That should not be possible.
> 
> That's not what Igor's diagram says - it's indicating the fact that
> is_running is being set to 1 in the process of context switching
> into vCPUx.
> 
Ah, ok. So I was right: I indeed was misunderstanding something, i.e.,
the diagram itself. :-)

Now I get it.

Sorry for the noise,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli

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