Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 227 insertions, 0 deletions

diff --git a/Documentation/misc-devices/ibmvmc.rst b/Documentation/misc-devices/ibmvmc.rst
new file mode 100644
index 000000000..b46df4ea2
--- /dev/null
+++ b/Documentation/misc-devices/ibmvmc.rst
@@ -0,0 +1,227 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+======================================================
+IBM Virtual Management Channel Kernel Driver (IBMVMC)
+======================================================
+
+:Authors:
+	Dave Engebretsen <engebret@us.ibm.com>,
+	Adam Reznechek <adreznec@linux.vnet.ibm.com>,
+	Steven Royer <seroyer@linux.vnet.ibm.com>,
+	Bryant G. Ly <bryantly@linux.vnet.ibm.com>,
+
+Introduction
+============
+
+Note: Knowledge of virtualization technology is required to understand
+this document.
+
+A good reference document would be:
+
+https://openpowerfoundation.org/wp-content/uploads/2016/05/LoPAPR_DRAFT_v11_24March2016_cmt1.pdf
+
+The Virtual Management Channel (VMC) is a logical device which provides an
+interface between the hypervisor and a management partition. This interface
+is like a message passing interface. This management partition is intended
+to provide an alternative to systems that use a Hardware Management
+Console (HMC) - based system management.
+
+The primary hardware management solution that is developed by IBM relies
+on an appliance server named the Hardware Management Console (HMC),
+packaged as an external tower or rack-mounted personal computer. In a
+Power Systems environment, a single HMC can manage multiple POWER
+processor-based systems.
+
+Management Application
+----------------------
+
+In the management partition, a management application exists which enables
+a system administrator to configure the system’s partitioning
+characteristics via a command line interface (CLI) or Representational
+State Transfer Application (REST API's).
+
+The management application runs on a Linux logical partition on a
+POWER8 or newer processor-based server that is virtualized by PowerVM.
+System configuration, maintenance, and control functions which
+traditionally require an HMC can be implemented in the management
+application using a combination of HMC to hypervisor interfaces and
+existing operating system methods. This tool provides a subset of the
+functions implemented by the HMC and enables basic partition configuration.
+The set of HMC to hypervisor messages supported by the management
+application component are passed to the hypervisor over a VMC interface,
+which is defined below.
+
+The VMC enables the management partition to provide basic partitioning
+functions:
+
+- Logical Partitioning Configuration
+- Start, and stop actions for individual partitions
+- Display of partition status
+- Management of virtual Ethernet
+- Management of virtual Storage
+- Basic system management
+
+Virtual Management Channel (VMC)
+--------------------------------
+
+A logical device, called the Virtual Management Channel (VMC), is defined
+for communicating between the management application and the hypervisor. It
+basically creates the pipes that enable virtualization management
+software. This device is presented to a designated management partition as
+a virtual device.
+
+This communication device uses Command/Response Queue (CRQ) and the
+Remote Direct Memory Access (RDMA) interfaces. A three-way handshake is
+defined that must take place to establish that both the hypervisor and
+management partition sides of the channel are running prior to
+sending/receiving any of the protocol messages.
+
+This driver also utilizes Transport Event CRQs. CRQ messages are sent
+when the hypervisor detects one of the peer partitions has abnormally
+terminated, or one side has called H_FREE_CRQ to close their CRQ.
+Two new classes of CRQ messages are introduced for the VMC device. VMC
+Administrative messages are used for each partition using the VMC to
+communicate capabilities to their partner. HMC Interface messages are used
+for the actual flow of HMC messages between the management partition and
+the hypervisor. As most HMC messages far exceed the size of a CRQ buffer,
+a virtual DMA (RMDA) of the HMC message data is done prior to each HMC
+Interface CRQ message. Only the management partition drives RDMA
+operations; hypervisors never directly cause the movement of message data.
+
+
+Terminology
+-----------
+RDMA
+        Remote Direct Memory Access is DMA transfer from the server to its
+        client or from the server to its partner partition. DMA refers
+        to both physical I/O to and from memory operations and to memory
+        to memory move operations.
+CRQ
+        Command/Response Queue a facility which is used to communicate
+        between partner partitions. Transport events which are signaled
+        from the hypervisor to partition are also reported in this queue.
+
+Example Management Partition VMC Driver Interface
+=================================================
+
+This section provides an example for the management application
+implementation where a device driver is used to interface to the VMC
+device. This driver consists of a new device, for example /dev/ibmvmc,
+which provides interfaces to open, close, read, write, and perform
+ioctl’s against the VMC device.
+
+VMC Interface Initialization
+----------------------------
+
+The device driver is responsible for initializing the VMC when the driver
+is loaded. It first creates and initializes the CRQ. Next, an exchange of
+VMC capabilities is performed to indicate the code version and number of
+resources available in both the management partition and the hypervisor.
+Finally, the hypervisor requests that the management partition create an
+initial pool of VMC buffers, one buffer for each possible HMC connection,
+which will be used for management application  session initialization.
+Prior to completion of this initialization sequence, the device returns
+EBUSY to open() calls. EIO is returned for all open() failures.
+
+::
+
+        Management Partition		Hypervisor
+                        CRQ INIT
+        ---------------------------------------->
+        	   CRQ INIT COMPLETE
+        <----------------------------------------
+        	      CAPABILITIES
+        ---------------------------------------->
+        	 CAPABILITIES RESPONSE
+        <----------------------------------------
+              ADD BUFFER (HMC IDX=0,1,..)         _
+        <----------------------------------------  |
+        	  ADD BUFFER RESPONSE              | - Perform # HMCs Iterations
+        ----------------------------------------> -
+
+VMC Interface Open
+------------------
+
+After the basic VMC channel has been initialized, an HMC session level
+connection can be established. The application layer performs an open() to
+the VMC device and executes an ioctl() against it, indicating the HMC ID
+(32 bytes of data) for this session. If the VMC device is in an invalid
+state, EIO will be returned for the ioctl(). The device driver creates a
+new HMC session value (ranging from 1 to 255) and HMC index value (starting
+at index 0 and ranging to 254) for this HMC ID. The driver then does an
+RDMA of the HMC ID to the hypervisor, and then sends an Interface Open
+message to the hypervisor to establish the session over the VMC. After the
+hypervisor receives this information, it sends Add Buffer messages to the
+management partition to seed an initial pool of buffers for the new HMC
+connection. Finally, the hypervisor sends an Interface Open Response
+message, to indicate that it is ready for normal runtime messaging. The
+following illustrates this VMC flow:
+
+::
+
+        Management Partition             Hypervisor
+        	      RDMA HMC ID
+        ---------------------------------------->
+        	    Interface Open
+        ---------------------------------------->
+        	      Add Buffer                  _
+        <----------------------------------------  |
+        	  Add Buffer Response              | - Perform N Iterations
+        ----------------------------------------> -
+        	Interface Open Response
+        <----------------------------------------
+
+VMC Interface Runtime
+---------------------
+
+During normal runtime, the management application and the hypervisor
+exchange HMC messages via the Signal VMC message and RDMA operations. When
+sending data to the hypervisor, the management application performs a
+write() to the VMC device, and the driver RDMA’s the data to the hypervisor
+and then sends a Signal Message. If a write() is attempted before VMC
+device buffers have been made available by the hypervisor, or no buffers
+are currently available, EBUSY is returned in response to the write(). A
+write() will return EIO for all other errors, such as an invalid device
+state. When the hypervisor sends a message to the management, the data is
+put into a VMC buffer and an Signal Message is sent to the VMC driver in
+the management partition. The driver RDMA’s the buffer into the partition
+and passes the data up to the appropriate management application via a
+read() to the VMC device. The read() request blocks if there is no buffer
+available to read. The management application may use select() to wait for
+the VMC device to become ready with data to read.
+
+::
+
+        Management Partition             Hypervisor
+        		MSG RDMA
+        ---------------------------------------->
+        		SIGNAL MSG
+        ---------------------------------------->
+        		SIGNAL MSG
+        <----------------------------------------
+        		MSG RDMA
+        <----------------------------------------
+
+VMC Interface Close
+-------------------
+
+HMC session level connections are closed by the management partition when
+the application layer performs a close() against the device. This action
+results in an Interface Close message flowing to the hypervisor, which
+causes the session to be terminated. The device driver must free any
+storage allocated for buffers for this HMC connection.
+
+::
+
+        Management Partition             Hypervisor
+        	     INTERFACE CLOSE
+        ---------------------------------------->
+                INTERFACE CLOSE RESPONSE
+        <----------------------------------------
+
+Additional Information
+======================
+
+For more information on the documentation for CRQ Messages, VMC Messages,
+HMC interface Buffers, and signal messages please refer to the Linux on
+Power Architecture Platform Reference. Section F.