nvdimm/region: Move cache management to the region driver

Now that cpu_cache_invalidate_memregion() is generically available, use
it to centralize CPU cache management in the nvdimm region driver.

This trades off removing redundant per-dimm CPU cache flushing with an
opportunistic flush on every region disable event to cover the case of
sensitive dirty data in the cache being written back to media after a
secure erase / overwrite event.

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/166993221550.1995348.16843505129579060258.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

3 files changed, 66 insertions, 1 deletions

diff --git a/drivers/nvdimm/region.c b/drivers/nvdimm/region.c
index 390123d293ea..88dc062af5f8 100644
--- a/drivers/nvdimm/region.c
+++ b/drivers/nvdimm/region.c
@@ -2,6 +2,7 @@
 /*
  * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
  */
+#include <linux/memregion.h>
 #include <linux/cpumask.h>
 #include <linux/module.h>
 #include <linux/device.h>
@@ -100,6 +101,16 @@ static void nd_region_remove(struct device *dev)
 	 */
 	sysfs_put(nd_region->bb_state);
 	nd_region->bb_state = NULL;
+
+	/*
+	 * Try to flush caches here since a disabled region may be subject to
+	 * secure erase while disabled, and previous dirty data should not be
+	 * written back to a new instance of the region. This only matters on
+	 * bare metal where security commands are available, so silent failure
+	 * here is ok.
+	 */
+	if (cpu_cache_has_invalidate_memregion())
+		cpu_cache_invalidate_memregion(IORES_DESC_PERSISTENT_MEMORY);
 }
 
 static int child_notify(struct device *dev, void *data)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index e0875d369762..83dbf398ea84 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -59,9 +59,51 @@ static int nvdimm_map_flush(struct device *dev, struct nvdimm *nvdimm, int dimm,
 	return 0;
 }
 
+static int nd_region_invalidate_memregion(struct nd_region *nd_region)
+{
+	int i, incoherent = 0;
+
+	for (i = 0; i < nd_region->ndr_mappings; i++) {
+		struct nd_mapping *nd_mapping = &nd_region->mapping[i];
+		struct nvdimm *nvdimm = nd_mapping->nvdimm;
+
+		if (test_bit(NDD_INCOHERENT, &nvdimm->flags)) {
+			incoherent++;
+			break;
+		}
+	}
+
+	if (!incoherent)
+		return 0;
+
+	if (!cpu_cache_has_invalidate_memregion()) {
+		if (IS_ENABLED(CONFIG_NVDIMM_SECURITY_TEST)) {
+			dev_warn(
+				&nd_region->dev,
+				"Bypassing cpu_cache_invalidate_memergion() for testing!\n");
+			goto out;
+		} else {
+			dev_err(&nd_region->dev,
+				"Failed to synchronize CPU cache state\n");
+			return -ENXIO;
+		}
+	}
+
+	cpu_cache_invalidate_memregion(IORES_DESC_PERSISTENT_MEMORY);
+out:
+	for (i = 0; i < nd_region->ndr_mappings; i++) {
+		struct nd_mapping *nd_mapping = &nd_region->mapping[i];
+		struct nvdimm *nvdimm = nd_mapping->nvdimm;
+
+		clear_bit(NDD_INCOHERENT, &nvdimm->flags);
+	}
+
+	return 0;
+}
+
 int nd_region_activate(struct nd_region *nd_region)
 {
-	int i, j, num_flush = 0;
+	int i, j, rc, num_flush = 0;
 	struct nd_region_data *ndrd;
 	struct device *dev = &nd_region->dev;
 	size_t flush_data_size = sizeof(void *);
@@ -85,6 +127,10 @@ int nd_region_activate(struct nd_region *nd_region)
 	}
 	nvdimm_bus_unlock(&nd_region->dev);
 
+	rc = nd_region_invalidate_memregion(nd_region);
+	if (rc)
+		return rc;
+
 	ndrd = devm_kzalloc(dev, sizeof(*ndrd) + flush_data_size, GFP_KERNEL);
 	if (!ndrd)
 		return -ENOMEM;
@@ -1222,3 +1268,5 @@ int nd_region_conflict(struct nd_region *nd_region, resource_size_t start,
 
 	return device_for_each_child(&nvdimm_bus->dev, &ctx, region_conflict);
 }
+
+MODULE_IMPORT_NS(DEVMEM);
diff --git a/drivers/nvdimm/security.c b/drivers/nvdimm/security.c
index 6814339b3dab..a03e3c45f297 100644
--- a/drivers/nvdimm/security.c
+++ b/drivers/nvdimm/security.c
@@ -208,6 +208,8 @@ static int __nvdimm_security_unlock(struct nvdimm *nvdimm)
 	rc = nvdimm->sec.ops->unlock(nvdimm, data);
 	dev_dbg(dev, "key: %d unlock: %s\n", key_serial(key),
 			rc == 0 ? "success" : "fail");
+	if (rc == 0)
+		set_bit(NDD_INCOHERENT, &nvdimm->flags);
 
 	nvdimm_put_key(key);
 	nvdimm->sec.flags = nvdimm_security_flags(nvdimm, NVDIMM_USER);
@@ -374,6 +376,8 @@ static int security_erase(struct nvdimm *nvdimm, unsigned int keyid,
 		return -ENOKEY;
 
 	rc = nvdimm->sec.ops->erase(nvdimm, data, pass_type);
+	if (rc == 0)
+		set_bit(NDD_INCOHERENT, &nvdimm->flags);
 	dev_dbg(dev, "key: %d erase%s: %s\n", key_serial(key),
 			pass_type == NVDIMM_MASTER ? "(master)" : "(user)",
 			rc == 0 ? "success" : "fail");
@@ -408,6 +412,8 @@ static int security_overwrite(struct nvdimm *nvdimm, unsigned int keyid)
 		return -ENOKEY;
 
 	rc = nvdimm->sec.ops->overwrite(nvdimm, data);
+	if (rc == 0)
+		set_bit(NDD_INCOHERENT, &nvdimm->flags);
 	dev_dbg(dev, "key: %d overwrite submission: %s\n", key_serial(key),
 			rc == 0 ? "success" : "fail");