mm/pagezero: Add stub driver to test registration API

Add the init/exit stubs to register a page clearing driver that
actually does nothing when called to allocate/clear memory.

Signed-off-by: Tony Luck <tony.luck@intel.com>

3 files changed, 90 insertions, 0 deletions

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 3be8f744ce2fc..d5b44d82eaca9 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -345,6 +345,16 @@ config INTEL_IDXD_KTEST
 
 	  If unsure, say N
 
+config INTEL_IDXD_PAGE_CLEAR
+	tristate "Intel DSA page clearing engine"
+	depends on INTEL_IDXD_SVM
+	help
+	  Driver to use DSA to allocate and clear kernel memory
+	  to build a pool of pre-zeroed 4KB pages on each node
+	  to speed up __GFP_ZERO allocations. User must manually
+	  configure a DSA work queue on each NUMA node before
+	  loading this driver.
+
 config INTEL_IOATDMA
 	tristate "Intel I/OAT DMA support"
 	depends on PCI && X86_64 && !UML
diff --git a/drivers/dma/idxd/Makefile b/drivers/dma/idxd/Makefile
index e761de91328a5..7ef558af17229 100644
--- a/drivers/dma/idxd/Makefile
+++ b/drivers/dma/idxd/Makefile
@@ -13,3 +13,5 @@ idxd_compat-y := compat.o
 
 obj-$(CONFIG_INTEL_IDXD_KTEST) += idxd_ktest.o
 idxd_ktest-y := ktest.o
+
+obj-$(CONFIG_INTEL_IDXD_PAGE_CLEAR) += dsa_page_clear_engine.o
diff --git a/drivers/dma/idxd/dsa_page_clear_engine.c b/drivers/dma/idxd/dsa_page_clear_engine.c
new file mode 100644
index 0000000000000..be6ed86ad4ee2
--- /dev/null
+++ b/drivers/dma/idxd/dsa_page_clear_engine.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2021 Intel Corporation */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/highmem.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+
+struct perzone {
+	void			*portal;
+	struct list_head	pages;
+};
+
+static void *alloc_engine_descriptor(int node)
+{
+	struct perzone *pz;
+
+	pz = kzalloc_node(sizeof(*pz),  GFP_KERNEL, node);
+	if (!pz)
+		return NULL;
+
+	INIT_LIST_HEAD(&pz->pages);
+
+	return pz;
+}
+
+/* Called with zone->lock held */
+int get_clear_pages(void *v, int migratetype, int want, struct list_head *l, int *countp)
+{
+	return 0;
+}
+
+/* Called with zone->lock held */
+void add_new_page(void *v, struct page *page)
+{
+}
+
+static int engine_cleanup(int node, void **v)
+{
+	struct perzone *pz;
+
+	if (!*v)
+		return 0;
+	pz = *v;
+
+	kfree(pz);
+	*v = NULL;
+
+	return 0;
+}
+
+static const struct page_clear_engine_ops dsa_page_engine_ops = {
+	.create = alloc_engine_descriptor,
+	.getpages = get_clear_pages,
+	.provide = add_new_page,
+	.clean = engine_cleanup,
+};
+
+static int __init init_page_clear_engine(void)
+{
+	int ret;
+
+	ret = register_page_clear_engine(&dsa_page_engine_ops);
+
+	return ret;
+}
+module_init(init_page_clear_engine);
+
+static void __exit exit_page_clear_driver(void)
+{
+	unregister_page_clear_engine(&dsa_page_engine_ops);
+}
+module_exit(exit_page_clear_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Jing Lin + Tony Luck");
+MODULE_DESCRIPTION("DSA page clear engine to zero pages");