Add a kselftest for the dax/kmem whole-device "state" sysfs attribute
(/sys/bus/dax/devices/daxX.Y/state), which transitions a kmem-backed
dax device between "unplugged", "online" and "online_movable".
The kselftest also includes a test to demonstrate the force-unbind
does not deadlock - but this is a destructive test. The dax device
can never be rebound after doing this.
Provisioning a devdax device and binding it to kmem needs daxctl/ndctl
out of scope for an in-tree selftest, so the test discovers an already
kmem-bound dax device and SKIPs when none are present or the memory
cannot be freed to reach a known baseline.
When a device is available it validates the interface contract:
- online / online_movable actually add memory (MemTotal grows),
- online is idempotent,
- switching between online types without unplug is rejected,
- unplug removes memory and the reported state is "unplugged"
- invalid input is rejected.
One specific regression test:
online -> unplug -> online_movable -> unplug
Re-online must re-reserve per-range resources so subsequent unplug
actually offlines and removes instead of silently reporting success
while the memory stays online.
Signed-off-by: Gregory Price <[email protected]>
---
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/dax/Makefile | 6 +
tools/testing/selftests/dax/config | 4 +
.../testing/selftests/dax/dax-kmem-hotplug.sh | 207 ++++++++++++++++++
tools/testing/selftests/dax/settings | 1 +
5 files changed, 219 insertions(+)
create mode 100644 tools/testing/selftests/dax/Makefile
create mode 100644 tools/testing/selftests/dax/config
create mode 100755 tools/testing/selftests/dax/dax-kmem-hotplug.sh
create mode 100644 tools/testing/selftests/dax/settings
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 6e59b8f63e41..8c2b4f97619c 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -14,6 +14,7 @@ TARGETS += core
TARGETS += cpufreq
TARGETS += cpu-hotplug
TARGETS += damon
+TARGETS += dax
TARGETS += devices/error_logs
TARGETS += devices/probe
TARGETS += dmabuf-heaps
diff --git a/tools/testing/selftests/dax/Makefile
b/tools/testing/selftests/dax/Makefile
new file mode 100644
index 000000000000..25a4f3d73a5b
--- /dev/null
+++ b/tools/testing/selftests/dax/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+all:
+
+TEST_PROGS := dax-kmem-hotplug.sh
+
+include ../lib.mk
diff --git a/tools/testing/selftests/dax/config
b/tools/testing/selftests/dax/config
new file mode 100644
index 000000000000..4c9aaeb6ceb4
--- /dev/null
+++ b/tools/testing/selftests/dax/config
@@ -0,0 +1,4 @@
+CONFIG_DEV_DAX=m
+CONFIG_DEV_DAX_KMEM=m
+CONFIG_MEMORY_HOTPLUG=y
+CONFIG_MEMORY_HOTREMOVE=y
diff --git a/tools/testing/selftests/dax/dax-kmem-hotplug.sh
b/tools/testing/selftests/dax/dax-kmem-hotplug.sh
new file mode 100755
index 000000000000..803bbd5a6409
--- /dev/null
+++ b/tools/testing/selftests/dax/dax-kmem-hotplug.sh
@@ -0,0 +1,207 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Exercise the dax/kmem "state" sysfs attribute:
+# /sys/bus/dax/devices/daxX.Y/state -> unplugged | online | online_movable
+#
+# The test needs a dax device already bound to the kmem driver.
+# If no suitable device is found the tests SKIP.
+#
+# A dax device can be provisioned with the memmap= boot param, e.g.:
+# memmap=2G!4G
+#
+# then, in the booted system:
+#
+# ndctl create-namespace -m devdax -e namespace0.0 -f
+# daxctl reconfigure-device -N -m system-ram dax0.0 # bind kmem
+# ./dax-kmem-hotplug.sh
+
+# shellcheck disable=SC1091
+DIR="$(dirname "$(readlink -f "$0")")"
+. "$DIR"/../kselftest/ktap_helpers.sh
+
+DAX_BASE=/sys/bus/dax/devices
+
+memtotal_kb() { awk '/^MemTotal:/ {print $2}' /proc/meminfo; }
+get_state() { cat "$HP" 2>/dev/null; }
+# set_state STATE -- write a state to the state attribute; returns the
+# write's exit status (0 = accepted by the kernel)
+set_state() { echo "$1" > "$HP" 2>/dev/null; }
+
+find_kmem_dax() {
+ local d drv
+ for d in "$DAX_BASE"/dax*; do
+ [ -e "$d/state" ] || continue
+ drv=$(readlink "$d/driver" 2>/dev/null)
+ [ "$(basename "${drv:-}")" = kmem ] || continue
+ basename "$d"
+ return 0
+ done
+ return 1
+}
+
+ktap_print_header
+
+if [ "$UID" != 0 ]; then
+ ktap_skip_all "must be run as root"
+ exit "$KSFT_SKIP"
+fi
+
+DAX=$(find_kmem_dax)
+if [ -z "$DAX" ]; then
+ ktap_skip_all "no kmem-bound dax device with a state attribute"
+ exit "$KSFT_SKIP"
+fi
+HP=$DAX_BASE/$DAX/state
+ORIG=$(get_state)
+
+# A failure to reach the baseline is environmental (memory in use), not an
+# interface failure, so skip rather than fail.
+set_state unplugged; rc=$?
+if [ "$rc" != 0 ] || [ "$(get_state)" != unplugged ]; then
+ ktap_skip_all "$DAX: cannot reach 'unplugged' baseline (memory in use?)"
+ [ -n "$ORIG" ] && set_state "$ORIG"
+ exit "$KSFT_SKIP"
+fi
+mt_unplugged=$(memtotal_kb)
+
+DRV=/sys/bus/dax/drivers/kmem
+AOB=/sys/devices/system/memory/auto_online_blocks
+
+ktap_print_msg "using $DAX (initial state was: $ORIG)"
+ktap_set_plan 11
+
+set_state online; rc=$?
+mt_online=$(memtotal_kb)
+if [ "$rc" = 0 ] && [ "$(get_state)" = online ] && [ "$mt_online" -gt
"$mt_unplugged" ]; then
+ ktap_test_pass "online: state=online, MemTotal $mt_unplugged ->
$mt_online kB"
+else
+ ktap_test_fail "online: rc=$rc state=$(get_state) MemTotal
$mt_unplugged -> $mt_online"
+fi
+
+set_state online; rc=$?
+if [ "$rc" = 0 ] && [ "$(get_state)" = online ]; then
+ ktap_test_pass "online idempotent"
+else
+ ktap_test_fail "online idempotent: rc=$rc state=$(get_state)"
+fi
+
+set_state online_movable; rc=$?
+if [ "$rc" != 0 ] && [ "$(get_state)" = online ]; then
+ ktap_test_pass "reject online_movable without intervening unplug"
+else
+ ktap_test_fail "online->online_movable not rejected: rc=$rc
state=$(get_state)"
+fi
+
+set_state unplugged; rc=$?
+mt=$(memtotal_kb)
+if [ "$rc" = 0 ] && [ "$(get_state)" = unplugged ] && [ "$mt" -lt "$mt_online"
]; then
+ ktap_test_pass "unplug from online: MemTotal $mt_online -> $mt kB"
+else
+ ktap_test_fail "unplug from online: rc=$rc state=$(get_state) MemTotal
$mt_online -> $mt"
+fi
+
+set_state online_movable; rc=$?
+mt_movable=$(memtotal_kb)
+if [ "$rc" = 0 ] && [ "$(get_state)" = online_movable ] && [ "$mt_movable" -gt
"$mt_unplugged" ]; then
+ ktap_test_pass "online_movable after unplug: MemTotal $mt_unplugged ->
$mt_movable kB"
+else
+ ktap_test_fail "online_movable after unplug: rc=$rc state=$(get_state)
MemTotal=$mt_movable"
+fi
+
+# The online -> unplug -> online_movable -> unplug cycle once regressed:
+# a re-online failed to re-reserve the per-range resources, so the final unplug
+# reported success while leaving the memory online. Assert it is really freed.
+set_state unplugged; rc=$?
+mt=$(memtotal_kb)
+if [ "$rc" != 0 ]; then
+ ktap_test_skip "unplug from movable not accepted (memory in use?)
rc=$rc"
+elif [ "$(get_state)" = unplugged ] && [ "$mt" -lt "$mt_movable" ]; then
+ ktap_test_pass "unplug from online_movable removed memory: $mt_movable
-> $mt kB"
+else
+ ktap_test_fail "unplug from movable reported success but memory
remained: state=$(get_state) MemTotal $mt_movable -> $mt"
+fi
+
+set_state online_kernel; rc=$?
+mt=$(memtotal_kb)
+if [ "$rc" = 0 ] && [ "$(get_state)" = online_kernel ] && [ "$mt" -gt
"$mt_unplugged" ]; then
+ ktap_test_pass "online_kernel: MemTotal $mt_unplugged -> $mt kB"
+else
+ ktap_test_fail "online_kernel: rc=$rc state=$(get_state) MemTotal=$mt"
+fi
+set_state unplugged
+
+before=$(get_state)
+set_state bogus_state; rc=$?
+if [ "$rc" != 0 ] && [ "$(get_state)" = "$before" ]; then
+ ktap_test_pass "reject invalid state string"
+else
+ ktap_test_fail "invalid state not rejected: rc=$rc state=$(get_state)"
+fi
+
+# Run several online/unplug cycles and require that each one adds/removes
memory
+set_state unplugged
+cycle_ok=1; fail_i=0
+for i in 1 2 3; do
+ if ! set_state online; then cycle_ok=0; fail_i=$i; break; fi
+ on=$(memtotal_kb)
+ if ! set_state unplugged; then cycle_ok=0; fail_i=$i; break; fi
+ off=$(memtotal_kb)
+ if [ "$on" -le "$mt_unplugged" ] || [ "$off" -ge "$on" ]; then
+ cycle_ok=0; fail_i=$i; break
+ fi
+done
+if [ "$cycle_ok" = 1 ]; then
+ ktap_test_pass "online/unplug cycle re-acquires resources (3x: memory
added and freed each time)"
+else
+ ktap_test_fail "online/unplug cycle regressed at iteration $fail_i
(on=$on off=$off baseline=$mt_unplugged)"
+fi
+
+# change system default online policy while the device is unbound, and show
+# the new system default policy is utilized across bindings.
+set_state unplugged
+if [ -w "$AOB" ] && [ -w "$DRV/unbind" ] && [ -w "$DRV/bind" ]; then
+ orig_aob=$(cat "$AOB")
+ echo "$DAX" > "$DRV/unbind" 2>/dev/null
+ echo offline > "$AOB" 2>/dev/null
+ echo "$DAX" > "$DRV/bind" 2>/dev/null
+ sleep 1
+ st=$(get_state)
+ echo "$orig_aob" > "$AOB" 2>/dev/null # restore system policy
+ if [ "$st" = offline ]; then
+ ktap_test_pass "online policy resolved at bind:
auto_online_blocks=offline -> state=offline"
+ else
+ ktap_test_fail "bind-time policy not honored: state=$st
(expected offline)"
+ fi
+ set_state unplugged 2>/dev/null
+else
+ ktap_test_skip "auto_online_blocks or driver bind/unbind not writable"
+fi
+
+[ -n "$ORIG" ] && set_state "$ORIG"
+
+# DESTRUCTIVE: unbinding the driver while memory is online causes the resources
+# to leak - but the unbind should not deadlock. Instead the driver leaks it
+# with a single "suck online" warning. This leaves the memory online and the
+# device unbound until reboot, so it runs last.
+set_state unplugged; set_state online
+if [ "$(get_state)" = online ] && [ -w "$DRV/unbind" ]; then
+ mt_on=$(memtotal_kb)
+ dmesg -C 2>/dev/null
+ echo "$DAX" > "$DRV/unbind" 2>/dev/null
+ mt_after=$(memtotal_kb)
+ # The leaked "System RAM (kmem)" regions stay in the iomem tree; reading
+ # their names dereferences res_name, which a buggy unbind already freed.
+ # Walk /proc/iomem to provoke that use-after-free (caught by KASAN).
+ cat /proc/iomem > /dev/null 2>&1
+ splat=$(dmesg 2>/dev/null | grep -ciE
"KASAN|BUG:|use-after-free|general protection|Oops|refcount_t")
+ if [ "$splat" = 0 ] && [ "$mt_after" -ge "$mt_on" ]; then
+ ktap_test_pass "unbind while online: memory left online, no
UAF/oops (MemTotal $mt_on -> $mt_after kB)"
+ else
+ ktap_test_fail "unbind while online regressed: splat=$splat
MemTotal $mt_on -> $mt_after kB"
+ fi
+else
+ ktap_test_skip "could not online device for unbind-while-online test"
+fi
+
+ktap_finished
diff --git a/tools/testing/selftests/dax/settings
b/tools/testing/selftests/dax/settings
new file mode 100644
index 000000000000..ba4d85f74cd6
--- /dev/null
+++ b/tools/testing/selftests/dax/settings
@@ -0,0 +1 @@
+timeout=90
--
2.54.0
