xen: correctly restore pfn_to_mfn_list_list after resume

pvops kernels >= 2.6.30 can currently only be saved and restored once. The
second attempt to save results in:

    ERROR Internal error: Frame# in pfn-to-mfn frame list is not in pseudophys
    ERROR Internal error: entry 0: p2m_frame_list[0] is 0xf2c2c2c2, max 0x120000
    ERROR Internal error: Failed to map/save the p2m frame list

I finally narrowed it down to:

    commit cdaead6b4e657f960d6d6f9f380e7dfeedc6a09b
        Author: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
        Date:   Fri Feb 27 15:34:59 2009 -0800

            xen: split construction of p2m mfn tables from registration

            Build the p2m_mfn_list_list early with the rest of the p2m table, but
            register it later when the real shared_info structure is in place.

            Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

The unforeseen side-effect of this change was to cause the mfn list list to not
be rebuilt on resume. Prior to this change it would have been rebuilt via
xen_post_suspend() -> xen_setup_shared_info() -> xen_setup_mfn_list_list().

Fix by explicitly calling xen_build_mfn_list_list() from xen_post_suspend().

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>

arch/x86/xen/mmu.c

@@ -185,7 +185,7 @@ static inline unsigned p2m_index(unsigned long pfn)
 }
 
 /* Build the parallel p2m_top_mfn structures */
-static void __init xen_build_mfn_list_list(void)
+void xen_build_mfn_list_list(void)
 {
 	unsigned pfn, idx;
 

arch/x86/xen/suspend.c

@@ -27,6 +27,8 @@ void xen_pre_suspend(void)
 
 void xen_post_suspend(int suspend_cancelled)
 {
+	xen_build_mfn_list_list();
+
 	xen_setup_shared_info();
 
 	if (suspend_cancelled) {

arch/x86/xen/xen-ops.h

@@ -25,6 +25,7 @@ extern struct shared_info *HYPERVISOR_shared_info;
 
 void xen_setup_mfn_list_list(void);
 void xen_setup_shared_info(void);
+void xen_build_mfn_list_list(void);
 void xen_setup_machphys_mapping(void);
 pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
 void xen_ident_map_ISA(void);