On Tue, 2017-09-05 at 15:06 -0700, Stefano Stabellini wrote: > On Tue, 5 Sep 2017, Dario Faggioli wrote: > > > > Re-checking things now, I actually do see that context_switch() on > > ARM > > is not 'terminal'. It call schedule_tail(), which on x86 does not > > return, while in ARM, it does. I must have confused these two... > > Sorry. > > > > Also, mostly out of curiosity, still looking at ARM code, I'm not > > getting at all how continue_new_vcpu() works (e.g., when/how is it > > invoked?). > > On ARM, context_switch() returns, unless it's the first time a new > vcpu > is run. In that case pc is set to continue_new_vcpu. __context_switch > restores pc to continue_new_vcpu, returning to it. > Ah, yes, that's what I was missing! The fact that PC is assigned the adress of continue_new_vcpu().. that's how it run. Only the first time, as you're explaining.
Thanks! :-) > From the second time onward a vcpu is run, > context_switch returns normally. > Right. And you (or someone else) can also confirm that the stack is per-vCPU? Or, in general, make sense out of the fact that the stack pointer register changes in such a way that, when we get back in do_softirq(), what's in the stack in the place where there was the 'cpu' local variable has (at least in some circumstances) changed? Regards, Dario -- <<This happens because I choose it to happen!>> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
signature.asc
Description: This is a digitally signed message part
_______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
