xen,kdump: handle pv domain in paddr_vmcoreinfo_note()

For kdump to work correctly it needs the physical address of
vmcoreinfo_note. When running as dom0 this means the virtual address
has to be translated to the related machine address.

paddr_vmcoreinfo_note() is meant to do the translation via
__pa_symbol() only, but being attributed "weak" it can be replaced
easily in Xen case.

Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Petr Tesarik <ptesarik@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

arch/x86/xen/mmu_pv.c

@@ -49,6 +49,9 @@
 #include <linux/memblock.h>
 #include <linux/seq_file.h>
 #include <linux/crash_dump.h>
+#ifdef CONFIG_KEXEC_CORE
+#include <linux/kexec.h>
+#endif
 
 #include <trace/events/xen.h>
 
@@ -2715,3 +2718,13 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
 	spin_unlock_irqrestore(&xen_reservation_lock, flags);
 }
 EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);
+
+#ifdef CONFIG_KEXEC_CORE
+phys_addr_t paddr_vmcoreinfo_note(void)
+{
+	if (xen_pv_domain())
+		return virt_to_machine(&vmcoreinfo_note).maddr;
+	else
+		return __pa_symbol(&vmcoreinfo_note);
+}
+#endif /* CONFIG_KEXEC_CORE */