s390/kexec: consolidate crash_map/unmap_reserved_pages() and arch_kexec_protect(unprotect)_crashkres()

Commit 3f625002581b ("kexec: introduce a protection mechanism for the
crashkernel reserved memory") is a similar mechanism for protecting the
crash kernel reserved memory to previous crash_map/unmap_reserved_pages()
implementation, the new one is more generic in name and cleaner in code
(besides, some arch may not be allowed to unmap the pgtable).

Therefore, this patch consolidates them, and uses the new
arch_kexec_protect(unprotect)_crashkres() to replace former
crash_map/unmap_reserved_pages() which by now has been only used by
S390.

The consolidation work needs the crash memory to be mapped initially,
this is done in machine_kdump_pm_init() which is after
reserve_crashkernel().  Once kdump kernel is loaded, the new
arch_kexec_protect_crashkres() implemented for S390 will actually
unmap the pgtable like before.

Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Minfei Huang <mhuang@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 7a0058ec78602da02b34fa2ae3afc523e90d1ab2)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

Author: Xunlei Pang

arch/s390/kernel/machine_kexec.c

@@ -83,13 +83,13 @@ static int machine_kdump_pm_cb(struct notifier_block *nb, unsigned long action,
 	switch (action) {
 	case PM_SUSPEND_PREPARE:
 	case PM_HIBERNATION_PREPARE:
-		if (crashk_res.start)
-			crash_map_reserved_pages();
+		if (kexec_crash_image)
+			arch_kexec_unprotect_crashkres();
 		break;
 	case PM_POST_SUSPEND:
 	case PM_POST_HIBERNATION:
-		if (crashk_res.start)
-			crash_unmap_reserved_pages();
+		if (kexec_crash_image)
+			arch_kexec_protect_crashkres();
 		break;
 	default:
 		return NOTIFY_DONE;
@@ -100,6 +100,8 @@ static int machine_kdump_pm_cb(struct notifier_block *nb, unsigned long action,
 static int __init machine_kdump_pm_init(void)
 {
 	pm_notifier(machine_kdump_pm_cb, 0);
+	/* Create initial mapping for crashkernel memory */
+	arch_kexec_unprotect_crashkres();
 	return 0;
 }
 arch_initcall(machine_kdump_pm_init);
@@ -134,6 +136,8 @@ static int kdump_csum_valid(struct kimage *image)
 #endif
 }
 
+#ifdef CONFIG_CRASH_DUMP
+
 /*
  * Map or unmap crashkernel memory
  */
@@ -155,21 +159,25 @@ static void crash_map_pages(int enable)
 }
 
 /*
- * Map crashkernel memory
+ * Unmap crashkernel memory
  */
-void crash_map_reserved_pages(void)
+void arch_kexec_protect_crashkres(void)
 {
-	crash_map_pages(1);
+	if (crashk_res.end)
+		crash_map_pages(0);
 }
 
 /*
- * Unmap crashkernel memory
+ * Map crashkernel memory
  */
-void crash_unmap_reserved_pages(void)
+void arch_kexec_unprotect_crashkres(void)
 {
-	crash_map_pages(0);
+	if (crashk_res.end)
+		crash_map_pages(1);
 }
 
+#endif
+
 /*
  * Give back memory to hypervisor before new kdump is loaded
  */

include/linux/kexec.h

@@ -241,8 +241,6 @@ extern void crash_kexec(struct pt_regs *);
 int kexec_should_crash(struct task_struct *);
 void crash_save_cpu(struct pt_regs *regs, int cpu);
 void crash_save_vmcoreinfo(void);
-void crash_map_reserved_pages(void);
-void crash_unmap_reserved_pages(void);
 void arch_crash_save_vmcoreinfo(void);
 __printf(1, 2)
 void vmcoreinfo_append_str(const char *fmt, ...);

kernel/kexec.c

@@ -136,9 +136,6 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 	if (ret)
 		return ret;
 
-	if (flags & KEXEC_ON_CRASH)
-		crash_map_reserved_pages();
-
 	if (flags & KEXEC_PRESERVE_CONTEXT)
 		image->preserve_context = 1;
 
@@ -161,12 +158,6 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 	if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
 		arch_kexec_protect_crashkres();
 
-	/*
-	 * Once the reserved memory is mapped, we should unmap this memory
-	 * before returning
-	 */
-	if (flags & KEXEC_ON_CRASH)
-		crash_unmap_reserved_pages();
 	kimage_free(image);
 	return ret;
 }
@@ -232,9 +223,6 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 
 	result = do_kexec_load(entry, nr_segments, segments, flags);
 
-	if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
-		arch_kexec_protect_crashkres();
-
 	mutex_unlock(&kexec_mutex);
 
 	return result;

kernel/kexec_core.c

@@ -926,7 +926,6 @@ int crash_shrink_memory(unsigned long new_size)
 	start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
 	end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
 
-	crash_map_reserved_pages();
 	crash_free_reserved_phys_range(end, crashk_res.end);
 
 	if ((start == end) && (crashk_res.parent != NULL))
@@ -940,7 +939,6 @@ int crash_shrink_memory(unsigned long new_size)
 	crashk_res.end = end - 1;
 
 	insert_resource(&iomem_resource, ram_res);
-	crash_unmap_reserved_pages();
 
 unlock:
 	mutex_unlock(&kexec_mutex);
@@ -1522,17 +1520,12 @@ int kernel_kexec(void)
 }
 
 /*
- * Add and remove page tables for crashkernel memory
+ * Protection mechanism for crashkernel reserved memory after
+ * the kdump kernel is loaded.
  *
  * Provide an empty default implementation here -- architecture
  * code may override this
  */
-void __weak crash_map_reserved_pages(void)
-{}
-
-void __weak crash_unmap_reserved_pages(void)
-{}
-
 void __weak arch_kexec_protect_crashkres(void)
 {}