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, 132 insertions, 0 deletions

diff --git a/Documentation/PCI/tph.rst b/Documentation/PCI/tph.rst
new file mode 100644
index 000000000..b6cf22b9b
--- /dev/null
+++ b/Documentation/PCI/tph.rst
@@ -0,0 +1,132 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+
+===========
+TPH Support
+===========
+
+:Copyright: 2024 Advanced Micro Devices, Inc.
+:Authors: - Eric van Tassell <eric.vantassell@amd.com>
+          - Wei Huang <wei.huang2@amd.com>
+
+
+Overview
+========
+
+TPH (TLP Processing Hints) is a PCIe feature that allows endpoint devices
+to provide optimization hints for requests that target memory space.
+These hints, in a format called Steering Tags (STs), are embedded in the
+requester's TLP headers, enabling the system hardware, such as the Root
+Complex, to better manage platform resources for these requests.
+
+For example, on platforms with TPH-based direct data cache injection
+support, an endpoint device can include appropriate STs in its DMA
+traffic to specify which cache the data should be written to. This allows
+the CPU core to have a higher probability of getting data from cache,
+potentially improving performance and reducing latency in data
+processing.
+
+
+How to Use TPH
+==============
+
+TPH is presented as an optional extended capability in PCIe. The Linux
+kernel handles TPH discovery during boot, but it is up to the device
+driver to request TPH enablement if it is to be utilized. Once enabled,
+the driver uses the provided API to obtain the Steering Tag for the
+target memory and to program the ST into the device's ST table.
+
+Enable TPH support in Linux
+---------------------------
+
+To support TPH, the kernel must be built with the CONFIG_PCIE_TPH option
+enabled.
+
+Manage TPH
+----------
+
+To enable TPH for a device, use the following function::
+
+  int pcie_enable_tph(struct pci_dev *pdev, int mode);
+
+This function enables TPH support for device with a specific ST mode.
+Current supported modes include:
+
+  * PCI_TPH_ST_NS_MODE - NO ST Mode
+  * PCI_TPH_ST_IV_MODE - Interrupt Vector Mode
+  * PCI_TPH_ST_DS_MODE - Device Specific Mode
+
+`pcie_enable_tph()` checks whether the requested mode is actually
+supported by the device before enabling. The device driver can figure out
+which TPH mode is supported and can be properly enabled based on the
+return value of `pcie_enable_tph()`.
+
+To disable TPH, use the following function::
+
+  void pcie_disable_tph(struct pci_dev *pdev);
+
+Manage ST
+---------
+
+Steering Tags are platform specific. PCIe spec does not specify where STs
+are from. Instead PCI Firmware Specification defines an ACPI _DSM method
+(see the `Revised _DSM for Cache Locality TPH Features ECN
+<https://members.pcisig.com/wg/PCI-SIG/document/15470>`_) for retrieving
+STs for a target memory of various properties. This method is what is
+supported in this implementation.
+
+To retrieve a Steering Tag for a target memory associated with a specific
+CPU, use the following function::
+
+  int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type type,
+                          unsigned int cpu, u16 *tag);
+
+The `type` argument is used to specify the memory type, either volatile
+or persistent, of the target memory. The `cpu` argument specifies the
+CPU where the memory is associated to.
+
+After the ST value is retrieved, the device driver can use the following
+function to write the ST into the device::
+
+  int pcie_tph_set_st_entry(struct pci_dev *pdev, unsigned int index,
+                            u16 tag);
+
+The `index` argument is the ST table entry index the ST tag will be
+written into. `pcie_tph_set_st_entry()` will figure out the proper
+location of ST table, either in the MSI-X table or in the TPH Extended
+Capability space, and write the Steering Tag into the ST entry pointed by
+the `index` argument.
+
+It is completely up to the driver to decide how to use these TPH
+functions. For example a network device driver can use the TPH APIs above
+to update the Steering Tag when interrupt affinity of a RX/TX queue has
+been changed. Here is a sample code for IRQ affinity notifier:
+
+.. code-block:: c
+
+    static void irq_affinity_notified(struct irq_affinity_notify *notify,
+                                      const cpumask_t *mask)
+    {
+         struct drv_irq *irq;
+         unsigned int cpu_id;
+         u16 tag;
+
+         irq = container_of(notify, struct drv_irq, affinity_notify);
+         cpumask_copy(irq->cpu_mask, mask);
+
+         /* Pick a right CPU as the target - here is just an example */
+         cpu_id = cpumask_first(irq->cpu_mask);
+
+         if (pcie_tph_get_cpu_st(irq->pdev, TPH_MEM_TYPE_VM, cpu_id,
+                                 &tag))
+             return;
+
+         if (pcie_tph_set_st_entry(irq->pdev, irq->msix_nr, tag))
+             return;
+    }
+
+Disable TPH system-wide
+-----------------------
+
+There is a kernel command line option available to control TPH feature:
+    * "notph": TPH will be disabled for all endpoint devices.