On 07/05/14 11:45, Stefano Stabellini wrote:

On Tue, 6 May 2014, David Vrabel wrote:

quoted

On 06/05/14 14:35, Stefano Stabellini wrote:

quoted

On Wed, 30 Apr 2014, David Vrabel wrote:

quoted

On 29/04/14 21:00, Arnd Bergmann wrote:

quoted

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.

quoted

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.

We do not want a different number of arguments to this hypercall.  Just
pass 0 for the MFN.  This hypercall docs should be updated to say this.

This doesn't seem any different to x86 HVM where the start_info_mfn
parameter is also not relevant.

	if (xen_hvm_domain()) {
		si.arg = 0UL;
		si.pre = NULL;
		si.post = &xen_hvm_post_suspend;
	} else {
		si.arg = virt_to_mfn(xen_start_info);
		si.pre = &xen_pre_suspend;
		si.post = &xen_post_suspend;
	}

Changing this to be !xen_pv_domain() would then do the right thing for arm.

xen_hvm_domain returns true on arm so that's not needed.
Unfortunately the patch turns out a bit ugly because of the way
hypercalls are implemented in assembly on arm and arm64.
Also I needed to provide quite a few empty stubs for other xen arch
specific functions.

Thanks.  If you want to add a commit message and apply to
devel/for-linus-3.16:

Reviewed-by: David Vrabel <redacted>

I wonder if the calls to xen_mm_pin_all() and xen_mm_unpin_all() could
be moved into the arch_pre_suspend() and arch_post_suspend() calls
instead. So there wouldn't need to be stubs provided for arm.

David