1 files changed, 120 insertions, 0 deletions
diff --git a/Documentation/fault-injection/nvme-fault-injection.rst b/Documentation/fault-injection/nvme-fault-injection.rst
new file mode 100644
index 000000000000..bbb1bf3e8650
--- /dev/null
+++ b/Documentation/fault-injection/nvme-fault-injection.rst
@@ -0,0 +1,120 @@
+NVMe Fault Injection
+====================
+Linux's fault injection framework provides a systematic way to support
+error injection via debugfs in the /sys/kernel/debug directory. When
+enabled, the default NVME_SC_INVALID_OPCODE with no retry will be
+injected into the nvme_end_request. Users can change the default status
+code and no retry flag via the debugfs. The list of Generic Command
+Status can be found in include/linux/nvme.h
+
+Following examples show how to inject an error into the nvme.
+
+First, enable CONFIG_FAULT_INJECTION_DEBUG_FS kernel config,
+recompile the kernel. After booting up the kernel, do the
+following.
+
+Example 1: Inject default status code with no retry
+---------------------------------------------------
+
+::
+
+  mount /dev/nvme0n1 /mnt
+  echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/times
+  echo 100 > /sys/kernel/debug/nvme0n1/fault_inject/probability
+  cp a.file /mnt
+
+Expected Result::
+
+  cp: cannot stat ‘/mnt/a.file’: Input/output error
+
+Message from dmesg::
+
+  FAULT_INJECTION: forcing a failure.
+  name fault_inject, interval 1, probability 100, space 0, times 1
+  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc8+ #2
+  Hardware name: innotek GmbH VirtualBox/VirtualBox,
+  BIOS VirtualBox 12/01/2006
+  Call Trace:
+    <IRQ>
+    dump_stack+0x5c/0x7d
+    should_fail+0x148/0x170
+    nvme_should_fail+0x2f/0x50 [nvme_core]
+    nvme_process_cq+0xe7/0x1d0 [nvme]
+    nvme_irq+0x1e/0x40 [nvme]
+    __handle_irq_event_percpu+0x3a/0x190
+    handle_irq_event_percpu+0x30/0x70
+    handle_irq_event+0x36/0x60
+    handle_fasteoi_irq+0x78/0x120
+    handle_irq+0xa7/0x130
+    ? tick_irq_enter+0xa8/0xc0
+    do_IRQ+0x43/0xc0
+    common_interrupt+0xa2/0xa2
+    </IRQ>
+  RIP: 0010:native_safe_halt+0x2/0x10
+  RSP: 0018:ffffffff82003e90 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffdd
+  RAX: ffffffff817a10c0 RBX: ffffffff82012480 RCX: 0000000000000000
+  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
+  RBP: 0000000000000000 R08: 000000008e38ce64 R09: 0000000000000000
+  R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff82012480
+  R13: ffffffff82012480 R14: 0000000000000000 R15: 0000000000000000
+    ? __sched_text_end+0x4/0x4
+    default_idle+0x18/0xf0
+    do_idle+0x150/0x1d0
+    cpu_startup_entry+0x6f/0x80
+    start_kernel+0x4c4/0x4e4
+    ? set_init_arg+0x55/0x55
+    secondary_startup_64+0xa5/0xb0
+    print_req_error: I/O error, dev nvme0n1, sector 9240
+  EXT4-fs error (device nvme0n1): ext4_find_entry:1436:
+  inode #2: comm cp: reading directory lblock 0
+
+Example 2: Inject default status code with retry
+------------------------------------------------
+
+::
+
+  mount /dev/nvme0n1 /mnt
+  echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/times
+  echo 100 > /sys/kernel/debug/nvme0n1/fault_inject/probability
+  echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/status
+  echo 0 > /sys/kernel/debug/nvme0n1/fault_inject/dont_retry
+
+  cp a.file /mnt
+
+Expected Result::
+
+  command success without error
+
+Message from dmesg::
+
+  FAULT_INJECTION: forcing a failure.
+  name fault_inject, interval 1, probability 100, space 0, times 1
+  CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.15.0-rc8+ #4
+  Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
+  Call Trace:
+    <IRQ>
+    dump_stack+0x5c/0x7d
+    should_fail+0x148/0x170
+    nvme_should_fail+0x30/0x60 [nvme_core]
+    nvme_loop_queue_response+0x84/0x110 [nvme_loop]
+    nvmet_req_complete+0x11/0x40 [nvmet]
+    nvmet_bio_done+0x28/0x40 [nvmet]
+    blk_update_request+0xb0/0x310
+    blk_mq_end_request+0x18/0x60
+    flush_smp_call_function_queue+0x3d/0xf0
+    smp_call_function_single_interrupt+0x2c/0xc0
+    call_function_single_interrupt+0xa2/0xb0
+    </IRQ>
+  RIP: 0010:native_safe_halt+0x2/0x10
+  RSP: 0018:ffffc9000068bec0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff04
+  RAX: ffffffff817a10c0 RBX: ffff88011a3c9680 RCX: 0000000000000000
+  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
+  RBP: 0000000000000001 R08: 000000008e38c131 R09: 0000000000000000
+  R10: 0000000000000000 R11: 0000000000000000 R12: ffff88011a3c9680
+  R13: ffff88011a3c9680 R14: 0000000000000000 R15: 0000000000000000
+    ? __sched_text_end+0x4/0x4
+    default_idle+0x18/0xf0
+    do_idle+0x150/0x1d0
+    cpu_startup_entry+0x6f/0x80
+    start_secondary+0x187/0x1e0
+    secondary_startup_64+0xa5/0xb0