libnvdimm: Introduce CONFIG_NVDIMM_SECURITY_TEST flag

nfit_test overrode the security_show() sysfs attribute function in nvdimm
dimm_devs in order to allow testing of security unlock. With the
introduction of CXL security commands, the trick to override
security_show() becomes significantly more complicated. By introdcing a
security flag CONFIG_NVDIMM_SECURITY_TEST, libnvdimm can just toggle the
check via a compile option. In addition the original override can can be
removed from tools/testing/nvdimm/.

The flag will also be used to bypass cpu_cache_invalidate_memregion() when
set in a different commit. This allows testing on QEMU with nfit_test or
cxl_test since cpu_cache_has_invalidate_memregion() checks whether
X86_FEATURE_HYPERVISOR cpu feature flag is set on x86.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/166983618758.2734609.18031639517065867138.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/Kconfig

@@ -114,4 +114,16 @@ config NVDIMM_TEST_BUILD
 	  core devm_memremap_pages() implementation and other
 	  infrastructure.
 
+config NVDIMM_SECURITY_TEST
+	bool "Enable NVDIMM security unit tests"
+	depends on NVDIMM_KEYS
+	help
+	  The NVDIMM and CXL subsystems support unit testing of their device
+	  security state machines. The NVDIMM_SECURITY_TEST option disables CPU
+	  cache maintenance operations around events like secure erase and
+	  overwrite.  Also, when enabled, the NVDIMM subsystem core helps the unit
+	  test implement a mock state machine.
+
+	  Select N if unsure.
+
 endif

drivers/nvdimm/dimm_devs.c

@@ -349,11 +349,18 @@ static ssize_t available_slots_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(available_slots);
 
-__weak ssize_t security_show(struct device *dev,
+ssize_t security_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
 	struct nvdimm *nvdimm = to_nvdimm(dev);
 
+	/*
+	 * For the test version we need to poll the "hardware" in order
+	 * to get the updated status for unlock testing.
+	 */
+	if (IS_ENABLED(CONFIG_NVDIMM_SECURITY_TEST))
+		nvdimm->sec.flags = nvdimm_security_flags(nvdimm, NVDIMM_USER);
+
 	if (test_bit(NVDIMM_SECURITY_OVERWRITE, &nvdimm->sec.flags))
 		return sprintf(buf, "overwrite\n");
 	if (test_bit(NVDIMM_SECURITY_DISABLED, &nvdimm->sec.flags))

drivers/nvdimm/security.c

@@ -177,6 +177,10 @@ static int __nvdimm_security_unlock(struct nvdimm *nvdimm)
 			|| !nvdimm->sec.flags)
 		return -EIO;
 
+	/* cxl_test needs this to pre-populate the security state */
+	if (IS_ENABLED(CONFIG_NVDIMM_SECURITY_TEST))
+		nvdimm->sec.flags = nvdimm_security_flags(nvdimm, NVDIMM_USER);
+
 	/* No need to go further if security is disabled */
 	if (test_bit(NVDIMM_SECURITY_DISABLED, &nvdimm->sec.flags))
 		return 0;

tools/testing/nvdimm/Kbuild

@@ -79,7 +79,6 @@ libnvdimm-$(CONFIG_BTT) += $(NVDIMM_SRC)/btt_devs.o
 libnvdimm-$(CONFIG_NVDIMM_PFN) += $(NVDIMM_SRC)/pfn_devs.o
 libnvdimm-$(CONFIG_NVDIMM_DAX) += $(NVDIMM_SRC)/dax_devs.o
 libnvdimm-$(CONFIG_NVDIMM_KEYS) += $(NVDIMM_SRC)/security.o
-libnvdimm-y += dimm_devs.o
 libnvdimm-y += libnvdimm_test.o
 libnvdimm-y += config_check.o