Re: [Xen-devel] [PATCH] Xen: hibernation is x86-only at the moment

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 30 Apr 2014, David Vrabel wrote:
> On 29/04/14 21:00, Arnd Bergmann wrote:
> > In commit 603fb42a66499ab "ARM: 8011/1: ARM hibernation / suspend-to-disk",
> > currently in linux-next, the ARM architecture gains support for
> > hibernation (suspend-to-disk). Xen supports this in principle, but only
> > has an architecture specific hypercall defined on x86, which leads
> > to a build error when both hibernation and Xen support are enabled:
> > 
> > drivers/xen/manage.c:105:2: error: implicit declaration of function 
> > 'HYPERVISOR_suspend' [-Werror=implicit-function-declaration]
> >   si->cancelled = HYPERVISOR_suspend(si->arg);
> > 
> > It is probably a good idea to define this hypercall on ARM as well
> > and provide an implementation in the host, but until that is done,
> > this patch helps disable the broken code in the Xen guest by making
> > it depend on CONFIG_X86.

Thanks Arnd.


> Since this isn't a regression in 3.15-rcX can you provide the
> appropriate hypercall on ARM.  This does not require that there is an
> implementation on Xen.
> 
> When the Xen implementation exists it will be easier to use if the
> support already exists in Linux.


The sched_on hypercall is already implemented on ARM.
However SCHEDOP_shutdown, defined as it is now, is unusable on ARM:

/*
 * Halt execution of this domain (all VCPUs) and notify the system controller.
 * @arg == pointer to sched_shutdown_t structure.
 *
 * If the sched_shutdown_t reason is SHUTDOWN_suspend then this
 * hypercall takes an additional extra argument which should be the
 * MFN of the guest's start_info_t.
 *
 * In addition, which reason is SHUTDOWN_suspend this hypercall
 * returns 1 if suspend was cancelled or the domain was merely
 * checkpointed, and 0 if it is resuming in a new domain.
 */
#define SCHEDOP_shutdown    2


We don't have a start_info, and even if we had, we wouldn't know the
MFN.
I think we should make it available on ARM only if we change the
interface making the third argument x86 only.  Of course that would
impact the linux side implementation too.

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