[S390] Add architecture code for unmapping crashkernel memory

This patch implements the crash_map_pages() function for s390.
KEXEC_CRASH_MEM_ALIGN is set to HPAGE_SIZE, in order to support
kernel mappings that use large pages. We also use HPAGE_SIZE alignment
for CONFIG_HUGETLB_PAGE=n in order to have the same 1 MiB alignment on
all s390 systems.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/kexec.h

@@ -36,6 +36,9 @@
 /* Allocate one page for the pdp and the second for the code */
 #define KEXEC_CONTROL_PAGE_SIZE 4096
 
+/* Alignment of crashkernel memory */
+#define KEXEC_CRASH_MEM_ALIGN HPAGE_SIZE
+
 /* The native architecture */
 #define KEXEC_ARCH KEXEC_ARCH_S390
 

arch/s390/kernel/machine_kexec.c

@@ -132,6 +132,37 @@ static int kdump_csum_valid(struct kimage *image)
 #endif
 }
 
+/*
+ * Map or unmap crashkernel memory
+ */
+static void crash_map_pages(int enable)
+{
+	unsigned long size = resource_size(&crashk_res);
+
+	BUG_ON(crashk_res.start % KEXEC_CRASH_MEM_ALIGN ||
+	       size % KEXEC_CRASH_MEM_ALIGN);
+	if (enable)
+		vmem_add_mapping(crashk_res.start, size);
+	else
+		vmem_remove_mapping(crashk_res.start, size);
+}
+
+/*
+ * Map crashkernel memory
+ */
+void crash_map_reserved_pages(void)
+{
+	crash_map_pages(1);
+}
+
+/*
+ * Unmap crashkernel memory
+ */
+void crash_unmap_reserved_pages(void)
+{
+	crash_map_pages(0);
+}
+
 /*
  * Give back memory to hypervisor before new kdump is loaded
  */

arch/s390/kernel/setup.c

@@ -446,6 +446,7 @@ static void __init setup_resources(void)
 		res->flags = IORESOURCE_BUSY | IORESOURCE_MEM;
 		switch (memory_chunk[i].type) {
 		case CHUNK_READ_WRITE:
+		case CHUNK_CRASHK:
 			res->name = "System RAM";
 			break;
 		case CHUNK_READ_ONLY:
@@ -720,8 +721,8 @@ static void __init reserve_crashkernel(void)
 			       &crash_base);
 	if (rc || crash_size == 0)
 		return;
-	crash_base = PAGE_ALIGN(crash_base);
-	crash_size = PAGE_ALIGN(crash_size);
+	crash_base = ALIGN(crash_base, KEXEC_CRASH_MEM_ALIGN);
+	crash_size = ALIGN(crash_size, KEXEC_CRASH_MEM_ALIGN);
 	if (register_memory_notifier(&kdump_mem_nb))
 		return;
 	if (!crash_base)
@@ -741,7 +742,7 @@ static void __init reserve_crashkernel(void)
 	crashk_res.start = crash_base;
 	crashk_res.end = crash_base + crash_size - 1;
 	insert_resource(&iomem_resource, &crashk_res);
-	reserve_kdump_bootmem(crash_base, crash_size, CHUNK_READ_WRITE);
+	reserve_kdump_bootmem(crash_base, crash_size, CHUNK_CRASHK);
 	pr_info("Reserving %lluMB of memory at %lluMB "
 		"for crashkernel (System RAM: %luMB)\n",
 		crash_size >> 20, crash_base >> 20, memory_end >> 20);
@@ -816,7 +817,8 @@ setup_memory(void)
 	for (i = 0; i < MEMORY_CHUNKS && memory_chunk[i].size > 0; i++) {
 		unsigned long start_chunk, end_chunk, pfn;
 
-		if (memory_chunk[i].type != CHUNK_READ_WRITE)
+		if (memory_chunk[i].type != CHUNK_READ_WRITE &&
+		    memory_chunk[i].type != CHUNK_CRASHK)
 			continue;
 		start_chunk = PFN_DOWN(memory_chunk[i].addr);
 		end_chunk = start_chunk + PFN_DOWN(memory_chunk[i].size);