Re: [Xen-devel] [PATCH RFC LINUX v1] xen: arm: enable migration on ARM.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2016-01-06 at 17:57 +0000, Stefano Stabellini wrote:
> On Wed, 6 Jan 2016, Stefano Stabellini wrote:
> > Please CC linux-arm for the non-RFC patches
> > 
> > On Wed, 9 Dec 2015, Ian Campbell wrote:
> > > Replace various stub functions with real functionality, including
> > > reestablishing the shared info page and the per-vcpu info pages on
> > > restore.
> > > 
> > > Reestablishing the vcpu info page is a little subtle. The
> > > VCPUOP_register_vcpu_info hypercall can only be called on either the
> > > current VCPU or on an offline different VCPU. Since migration occurs
> > > with all VCPUS online they are all therefore online at the point of
> > > resume.
> > > 
> > > Therefore we must perform a cross VCPU call to each non-boot VCPU,
> > > which cannot be done in the xen_arch_post_suspend() callback since
> > > that is run from stop_machine() with interrupts disabled.
> > > 
> > > Furthermore VCPUOP_register_vcpu_info can only be called once per-
> > > VCPU
> > > in a given domain, so it must not be called after a cancelled suspend
> > > (which resumes in the same domain).
> > > 
> > > Therefore xen_arch_resume() gains a suspend_cancelled parameter and
> > > we
> > > resume the secondary VCPUs there only if needed.
> > 
> > This is a bit complex, maybe we could use a cpu notifier like we do on
> > x86?
> 
> Sorry forget this email, it was sent by mistake.

Too late, you may ignore my reply though ;-)


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