Re: [Xen-devel] [PATCH v3 0/1] Introduce VCPUOP_reset_vcpu_info

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Aug 19, 2014 at 07:59:52PM +0100, David Vrabel wrote:
> On 19/08/14 11:04, Vitaly Kuznetsov wrote:
> >The patch and guest code are based on the prototype by Konrad Rzeszutek Wilk.
> >
> >VCPUOP_reset_vcpu_info is required to support kexec performed by smp pvhvm
> >guest. It was tested with the guest code listed below.
> 
> Instead of having the guest teardown all these bits of  setup.  I think it
> would be preferable to have the toolstack build a new domain with the same
> memory contents from the original VM.  The toolstack would then start this
> new domain at the kexec entry point.

What about kdump case /crash case? We might crash at anytime and would
want to start the kdump kernel which hopefully can reset all of the VCPU
information such that it can boot with more than one VCPU.

> 
> The advantage of this is you don't need to add new hypercall sub-ops to
> teardown all bits and pieces, both for existing stuff and for anything new
> that might be added.

Sure, except that having an setup and teardown paths provide a nice
symetrical states. Doing an 'kexec_guest' hypercall seems to be just
a workaround that and giving up on the symmetry.

My feeling is that we really ought to have 'init' and 'teardown'
for every hypercall. That would also be good to test the locking, memory
leaks, etc.

> 
> David
> 
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