[Xen-devel] [RFC PATCH 0/3] Improve kexec support in Xen hypervisor

[Daniel Kiper]

On Thu, Jan 17, 2013 at 11:37:48AM +0000, Andrew Cooper wrote:
> On 17/01/13 11:27, Daniel Kiper wrote:
> > On Wed, Jan 16, 2013 at 04:29:03PM +0000, David Vrabel wrote:
> >> This series of patches improves the kexec hypercall in the Xen
> >> hypervisor.  It is an incomplete prototype but I posting it early for
> >> comments on the proposed ABI/API.
> >>
> >> This allows a privileged Xen guest to load kexec images into the
> >> hypervisor from a userspace tool without using the Linux kernel's
> >> kexec subsystem.  It is the first step to supporting kexec of crash
> >> kernels from a pv-ops dom0 kernel (the required kernel and kexec-tools
> >> patches will be posted later).
> >>
> >> The kernel will require a kexec hypercall somewhere in the
> >> crash_kexec() path to actually exec the loaded image.  Any preferences
> >> on how the hook for this should be implemented?  Note that the kernel
> > This should be implemented as stub which be called by machine_kexec()
> > and later it would call relevant hypercall.
> >
> >> won't be aware that an image as been loaded as it is loaded directly
> >> into the hypervisor and not via the kernel's kexec_load system call.
> > Maybe we should have sepcial kexec hypercall function which allow us
> > to ask hypervisor that image is loaded or not.
> 
> But we already have this information.  If the kexec crash hypercall
> returns back to dom0 then a crash kernel is not loaded.
> 
> One could certainly argue that even if a crash kernel is not loaded, a
> kexec crash hypercall means that dom0 is in bad state and Xen should
> panic() anyway, which is the case on any other form of dom0 crash.

I thought about somthing which does not do big bang when kexec image is loaded.
Now I think that it should return what type of image is loaded
(crash and/or regular one).

Daniel