ACPI / APEI: Switch estatus pool to use vmalloc memory

The ghes code is careful to parse and round firmware's advertised
memory requirements for CPER records, up to a maximum of 64K.
However when ghes_estatus_pool_expand() does its work, it splits
the requested size into PAGE_SIZE granules.

This means if firmware generates 5K of CPER records, and correctly
describes this in the table, __process_error() will silently fail as it
is unable to allocate more than PAGE_SIZE.

Switch the estatus pool to vmalloc() memory. On x86 vmalloc() memory
may fault and be fixed up by vmalloc_fault(). To prevent this call
vmalloc_sync_all() before an NMI handler could discover the memory.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/apei/ghes.c

@@ -170,40 +170,40 @@ static int ghes_estatus_pool_init(void)
 	return 0;
 }
 
-static void ghes_estatus_pool_free_chunk_page(struct gen_pool *pool,
+static void ghes_estatus_pool_free_chunk(struct gen_pool *pool,
 					      struct gen_pool_chunk *chunk,
 					      void *data)
 {
-	free_page(chunk->start_addr);
+	vfree((void *)chunk->start_addr);
 }
 
 static void ghes_estatus_pool_exit(void)
 {
 	gen_pool_for_each_chunk(ghes_estatus_pool,
-				ghes_estatus_pool_free_chunk_page, NULL);
+				ghes_estatus_pool_free_chunk, NULL);
 	gen_pool_destroy(ghes_estatus_pool);
 }
 
 static int ghes_estatus_pool_expand(unsigned long len)
 {
-	unsigned long i, pages, size, addr;
-	int ret;
+	unsigned long size, addr;
 
 	ghes_estatus_pool_size_request += PAGE_ALIGN(len);
 	size = gen_pool_size(ghes_estatus_pool);
 	if (size >= ghes_estatus_pool_size_request)
 		return 0;
-	pages = (ghes_estatus_pool_size_request - size) / PAGE_SIZE;
-	for (i = 0; i < pages; i++) {
-		addr = __get_free_page(GFP_KERNEL);
-		if (!addr)
-			return -ENOMEM;
-		ret = gen_pool_add(ghes_estatus_pool, addr, PAGE_SIZE, -1);
-		if (ret)
-			return ret;
-	}
 
-	return 0;
+	addr = (unsigned long)vmalloc(PAGE_ALIGN(len));
+	if (!addr)
+		return -ENOMEM;
+
+	/*
+	 * New allocation must be visible in all pgd before it can be found by
+	 * an NMI allocating from the pool.
+	 */
+	vmalloc_sync_all();
+
+	return gen_pool_add(ghes_estatus_pool, addr, PAGE_ALIGN(len), -1);
 }
 
 static int map_gen_v2(struct ghes *ghes)