From 782694f9aeff6e146cfd00b31822995790546175 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Sun, 23 Jan 2022 16:54:22 -0800
Subject: [PATCH 115/217] cxl/memdev: Enable / disable support

Introduce the 'cxl {enable,disable}-memdev' commands. When a memdev is
disabled the ports in the topology may be unregistered. CXL memory regions
require each endpoint in the interleave to attach to the cxl_mem driver
before regions are activated.

Note that this starts out with the deliberate bug that it has false
positive detection of active memdevs. The fix for that bug requires kernel
support to detect the device's active participation in a region, until then
require all disable attempts to specify the --force override. This way
there are never any releases of cxl-cli that lack disable-memdev safety.

Link: https://lore.kernel.org/r/164298566245.3021641.12696907310209056878.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 Documentation/cxl/cxl-disable-memdev.txt | 37 +++++++++++++++
 Documentation/cxl/cxl-enable-memdev.txt  | 34 ++++++++++++++
 Documentation/cxl/lib/libcxl.txt         | 23 +++++++++
 Documentation/cxl/meson.build            |  2 +
 cxl/builtin.h                            |  2 +
 cxl/cxl.c                                |  2 +
 cxl/lib/libcxl.c                         | 58 +++++++++++++++++++++++
 cxl/lib/libcxl.sym                       |  2 +
 cxl/libcxl.h                             |  2 +
 cxl/memdev.c                             | 60 +++++++++++++++++++++++-
 10 files changed, 221 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/cxl/cxl-disable-memdev.txt
 create mode 100644 Documentation/cxl/cxl-enable-memdev.txt

diff --git a/Documentation/cxl/cxl-disable-memdev.txt b/Documentation/cxl/cxl-disable-memdev.txt
new file mode 100644
index 0000000..edd5385
--- /dev/null
+++ b/Documentation/cxl/cxl-disable-memdev.txt
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+
+cxl-disable-memdev(1)
+=====================
+
+NAME
+----
+cxl-disable-memdev - deactivate / hot-remove a given CXL memdev
+
+SYNOPSIS
+--------
+[verse]
+'cxl disable-memdev' <mem0> [<mem1>..<memN>] [<options>]
+
+
+OPTIONS
+-------
+<memory device(s)>::
+include::memdev-option.txt[]
+
+-f::
+--force::
+	DANGEROUS: Override the safety measure that blocks attempts to disable
+	a device if the tool determines the memdev is in active usage. Recall
+	that CXL memory ranges might have been established by platform
+	firmware and disabling an active device is akin to force removing
+	memory from a running system.
+
+-v::
+	Turn on verbose debug messages in the library (if libcxl was built with
+	logging and debug enabled).
+
+include::../copyright.txt[]
+
+SEE ALSO
+--------
+linkcxl:cxl-enable-memdev[1]
diff --git a/Documentation/cxl/cxl-enable-memdev.txt b/Documentation/cxl/cxl-enable-memdev.txt
new file mode 100644
index 0000000..088d5e0
--- /dev/null
+++ b/Documentation/cxl/cxl-enable-memdev.txt
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+
+cxl-enable-memdev(1)
+====================
+
+NAME
+----
+cxl-enable-memdev - activate / hot-add a given CXL memdev
+
+SYNOPSIS
+--------
+[verse]
+'cxl enable-memdev' <mem0> [<mem1>..<memN>] [<options>]
+
+A memdev typically autoenables at initial device discovery. However, if
+it was manually disabled this command can trigger the kernel to activate
+it again. This involves detecting the state of the HDM (Host Managed
+Device Memory) Decoders and validating that CXL.mem is enabled for each
+port in the device's hierarchy.
+
+OPTIONS
+-------
+<memory device(s)>::
+include::memdev-option.txt[]
+
+-v::
+	Turn on verbose debug messages in the library (if libcxl was built with
+	logging and debug enabled).
+
+include::../copyright.txt[]
+
+SEE ALSO
+--------
+linkcxl:cxl-disable-memdev[1]
diff --git a/Documentation/cxl/lib/libcxl.txt b/Documentation/cxl/lib/libcxl.txt
index de88d19..49edb71 100644
--- a/Documentation/cxl/lib/libcxl.txt
+++ b/Documentation/cxl/lib/libcxl.txt
@@ -93,6 +93,29 @@ device.
 cxl_memdev_get_numa_node() returns the affinitized CPU node number if
 available or -1 otherwise.
 
+=== MEMDEV: Control
+----
+int cxl_memdev_disable_invalidate(struct cxl_memdev *memdev);
+int cxl_memdev_enable(struct cxl_memdev *memdev);
+----
+When a memory device is disabled it unregisters its associated endpoints
+and potentially intervening switch ports if there are no other memdevs
+pinning that port active. That means that any existing port objects that
+the library has previously returned are in valid and need to be re-read.
+Callers must be careful to re-retrieve port objects after
+cxl_memdev_disable_invalidate(). Any usage of a previously obtained port
+object after a cxl_memdev_disable_invalidate() call is a use-after-free
+programming error. It follows that after cxl_memdev_enable() new ports
+may appear in the topology that were not previously enumerable.
+
+NOTE: cxl_memdev_disable_invalidate() will force disable the memdev
+regardless of whether the memory provided by the device is in active use
+by the operating system. Callers take responisbility for assuring that
+it is safe to disable the memory device. Otherwise, this call can be as
+destructive as ripping a DIMM out of a running system. Like all other
+libcxl calls that mutate the system state or divulge security sensitive
+information this call requires root / CAP_SYS_ADMIN.
+
 === MEMDEV: Commands
 ----
 struct cxl_cmd *cxl_cmd_new_raw(struct cxl_memdev *memdev, int opcode);
diff --git a/Documentation/cxl/meson.build b/Documentation/cxl/meson.build
index 0a6346b..7618c97 100644
--- a/Documentation/cxl/meson.build
+++ b/Documentation/cxl/meson.build
@@ -30,6 +30,8 @@ cxl_manpages = [
   'cxl-read-labels.txt',
   'cxl-write-labels.txt',
   'cxl-zero-labels.txt',
+  'cxl-enable-memdev.txt',
+  'cxl-disable-memdev.txt',
 ]
 
 foreach man : cxl_manpages
diff --git a/cxl/builtin.h b/cxl/builtin.h
index 78eca6e..621c85c 100644
--- a/cxl/builtin.h
+++ b/cxl/builtin.h
@@ -10,4 +10,6 @@ int cmd_read_labels(int argc, const char **argv, struct cxl_ctx *ctx);
 int cmd_zero_labels(int argc, const char **argv, struct cxl_ctx *ctx);
 int cmd_init_labels(int argc, const char **argv, struct cxl_ctx *ctx);
 int cmd_check_labels(int argc, const char **argv, struct cxl_ctx *ctx);
+int cmd_disable_memdev(int argc, const char **argv, struct cxl_ctx *ctx);
+int cmd_enable_memdev(int argc, const char **argv, struct cxl_ctx *ctx);
 #endif /* _CXL_BUILTIN_H_ */
diff --git a/cxl/cxl.c b/cxl/cxl.c
index 4b1661d..78d2e9a 100644
--- a/cxl/cxl.c
+++ b/cxl/cxl.c
@@ -64,6 +64,8 @@ static struct cmd_struct commands[] = {
 	{ "zero-labels", .c_fn = cmd_zero_labels },
 	{ "read-labels", .c_fn = cmd_read_labels },
 	{ "write-labels", .c_fn = cmd_write_labels },
+	{ "disable-memdev", .c_fn = cmd_disable_memdev },
+	{ "enable-memdev", .c_fn = cmd_enable_memdev },
 };
 
 int main(int argc, const char **argv)
diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
index 14c7db8..2fdaf71 100644
--- a/cxl/lib/libcxl.c
+++ b/cxl/lib/libcxl.c
@@ -500,6 +500,64 @@ CXL_EXPORT const char *cxl_memdev_get_firmware_verison(struct cxl_memdev *memdev
 	return memdev->firmware_version;
 }
 
+CXL_EXPORT int cxl_memdev_disable_invalidate(struct cxl_memdev *memdev)
+{
+	struct cxl_ctx *ctx = cxl_memdev_get_ctx(memdev);
+	const char *devname = cxl_memdev_get_devname(memdev);
+	struct cxl_port *port, *_p, *bus_port;
+	struct cxl_bus *bus;
+
+	if (!cxl_memdev_is_enabled(memdev))
+		return 0;
+
+	bus = cxl_memdev_get_bus(memdev);
+	if (!bus) {
+		err(ctx, "%s: failed to invalidate\n", devname);
+		return -ENXIO;
+	}
+
+	util_unbind(memdev->dev_path, ctx);
+
+	if (cxl_memdev_is_enabled(memdev)) {
+		err(ctx, "%s: failed to disable\n", devname);
+		return -EBUSY;
+	}
+
+	/*
+	 * The state of all ports is now indeterminate, delete them all
+	 * and start over.
+	 */
+	bus_port = cxl_bus_get_port(bus);
+	list_for_each_safe(&bus_port->child_ports, port, _p, list)
+		free_port(port, &bus_port->child_ports);
+	bus_port->ports_init = 0;
+	memdev->endpoint = NULL;
+
+	dbg(ctx, "%s: disabled\n", devname);
+
+	return 0;
+}
+
+CXL_EXPORT int cxl_memdev_enable(struct cxl_memdev *memdev)
+{
+	struct cxl_ctx *ctx = cxl_memdev_get_ctx(memdev);
+	const char *devname = cxl_memdev_get_devname(memdev);
+
+	if (cxl_memdev_is_enabled(memdev))
+		return 0;
+
+	util_bind(devname, memdev->module, "cxl", ctx);
+
+	if (!cxl_memdev_is_enabled(memdev)) {
+		err(ctx, "%s: failed to enable\n", devname);
+		return -ENXIO;
+	}
+
+	dbg(ctx, "%s: enabled\n", devname);
+
+	return 0;
+}
+
 static struct cxl_endpoint *cxl_port_find_endpoint(struct cxl_port *parent_port,
 						   struct cxl_memdev *memdev)
 {
diff --git a/cxl/lib/libcxl.sym b/cxl/lib/libcxl.sym
index b13a2d6..f235e99 100644
--- a/cxl/lib/libcxl.sym
+++ b/cxl/lib/libcxl.sym
@@ -115,4 +115,6 @@ global:
 	cxl_memdev_get_endpoint;
 	cxl_memdev_is_enabled;
 	cxl_memdev_get_bus;
+	cxl_memdev_disable_invalidate;
+	cxl_memdev_enable;
 } LIBCXL_1;
diff --git a/cxl/libcxl.h b/cxl/libcxl.h
index be656ed..53f68dd 100644
--- a/cxl/libcxl.h
+++ b/cxl/libcxl.h
@@ -48,6 +48,8 @@ unsigned long long cxl_memdev_get_pmem_size(struct cxl_memdev *memdev);
 unsigned long long cxl_memdev_get_ram_size(struct cxl_memdev *memdev);
 const char *cxl_memdev_get_firmware_verison(struct cxl_memdev *memdev);
 size_t cxl_memdev_get_label_size(struct cxl_memdev *memdev);
+int cxl_memdev_disable_invalidate(struct cxl_memdev *memdev);
+int cxl_memdev_enable(struct cxl_memdev *memdev);
 struct cxl_endpoint;
 struct cxl_endpoint *cxl_memdev_get_endpoint(struct cxl_memdev *memdev);
 int cxl_memdev_nvdimm_bridge_active(struct cxl_memdev *memdev);
diff --git a/cxl/memdev.c b/cxl/memdev.c
index ef5343a..90b33e1 100644
--- a/cxl/memdev.c
+++ b/cxl/memdev.c
@@ -25,13 +25,14 @@ static struct parameters {
 	unsigned offset;
 	bool verbose;
 	bool serial;
+	bool force;
 } param;
 
 static struct log_ctx ml;
 
 #define BASE_OPTIONS() \
 OPT_BOOLEAN('v',"verbose", &param.verbose, "turn on debug"), \
-OPT_BOOLEAN('S', "serial", &param.serial, "user serials numbers to id memdevs")
+OPT_BOOLEAN('S', "serial", &param.serial, "use serial numbers to id memdevs")
 
 #define READ_OPTIONS() \
 OPT_STRING('o', "output", &param.outfile, "output-file", \
@@ -46,6 +47,10 @@ OPT_UINTEGER('s', "size", &param.len, "number of label bytes to operate"), \
 OPT_UINTEGER('O', "offset", &param.offset, \
 	"offset into the label area to start operation")
 
+#define DISABLE_OPTIONS()                                              \
+OPT_BOOLEAN('f', "force", &param.force,                                \
+	    "DANGEROUS: override active memdev safety checks")
+
 static const struct option read_options[] = {
 	BASE_OPTIONS(),
 	LABEL_OPTIONS(),
@@ -66,6 +71,37 @@ static const struct option zero_options[] = {
 	OPT_END(),
 };
 
+static const struct option disable_options[] = {
+	BASE_OPTIONS(),
+	DISABLE_OPTIONS(),
+	OPT_END(),
+};
+
+static const struct option enable_options[] = {
+	BASE_OPTIONS(),
+	OPT_END(),
+};
+
+static int action_disable(struct cxl_memdev *memdev, struct action_context *actx)
+{
+	if (!cxl_memdev_is_enabled(memdev))
+		return 0;
+
+	if (!param.force) {
+		/* TODO: actually detect rather than assume active */
+		log_err(&ml, "%s is part of an active region\n",
+			cxl_memdev_get_devname(memdev));
+		return -EBUSY;
+	}
+
+	return cxl_memdev_disable_invalidate(memdev);
+}
+
+static int action_enable(struct cxl_memdev *memdev, struct action_context *actx)
+{
+	return cxl_memdev_enable(memdev);
+}
+
 static int action_zero(struct cxl_memdev *memdev, struct action_context *actx)
 {
 	size_t size;
@@ -340,3 +376,25 @@ int cmd_zero_labels(int argc, const char **argv, struct cxl_ctx *ctx)
 		 count > 1 ? "s" : "");
 	return count >= 0 ? 0 : EXIT_FAILURE;
 }
+
+int cmd_disable_memdev(int argc, const char **argv, struct cxl_ctx *ctx)
+{
+	int count = memdev_action(
+		argc, argv, ctx, action_disable, disable_options,
+		"cxl disable-memdev <mem0> [<mem1>..<memN>] [<options>]");
+
+	log_info(&ml, "disabled %d mem%s\n", count >= 0 ? count : 0,
+		 count > 1 ? "s" : "");
+	return count >= 0 ? 0 : EXIT_FAILURE;
+}
+
+int cmd_enable_memdev(int argc, const char **argv, struct cxl_ctx *ctx)
+{
+	int count = memdev_action(
+		argc, argv, ctx, action_enable, enable_options,
+		"cxl enable-memdev <mem0> [<mem1>..<memN>] [<options>]");
+
+	log_info(&ml, "enabled %d mem%s\n", count >= 0 ? count : 0,
+		 count > 1 ? "s" : "");
+	return count >= 0 ? 0 : EXIT_FAILURE;
+}
-- 
2.27.0