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authorLinus Torvalds <torvalds@linux-foundation.org>2018-02-09 09:58:37 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-02-09 09:58:37 -0800
commitdff839f27dc8d70e191562c8e78b0a9a88028362 (patch)
tree58173c5913ee68e0d8acc8ef31808bbe416d3758 /Documentation/driver-api/s390-drivers.rst
parent54ce685cae30c106f062d714c11e644ab1b93b51 (diff)
parent48973df8c9c51612acc870ad1a885b0cf27c3356 (diff)
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Pull s390 updates from Heiko Carstens: "The main thing in this merge is the defense for the Spectre vulnerabilities. But there are other updates as well, the changes in more detail: - An s390 specific implementation of the array_index_mask_nospec function to the defense against spectre v1 - Two patches to utilize the new PPA-12/PPA-13 instructions to run the kernel and/or user space with reduced branch predicton. - The s390 variant of the 'retpoline' spectre v2 defense called 'expoline'. There is no return instruction for s390, instead an indirect branch is used for function return The s390 defense mechanism for indirect branches works by using an execute-type instruction with the indirect branch as the target of the execute. In effect that turns off the prediction for the indirect branch. - Scrub registers in entry.S that contain user controlled values to prevent the speculative use of these values. - Re-add the second parameter for the s390 specific runtime instrumentation system call and move the header file to uapi. The second parameter will continue to do nothing but older kernel versions only accepted valid real-time signal numbers. The details will be documented in the man-page for the system call. - Corrections and improvements for the s390 specific documentation - Add a line to /proc/sysinfo to display the CPU model dependent license-internal-code identifier - A header file include fix for eadm. - An error message fix in the kprobes code. - The removal of an outdated ARCH_xxx select statement" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: s390/kconfig: Remove ARCH_WANTS_PROT_NUMA_PROT_NONE select s390: introduce execute-trampolines for branches s390: run user space and KVM guests with modified branch prediction s390: add options to change branch prediction behaviour for the kernel s390/alternative: use a copy of the facility bit mask s390: add optimized array_index_mask_nospec s390: scrub registers on kernel entry and KVM exit s390/cio: fix kernel-doc usage s390/runtime_instrumentation: re-add signum system call parameter s390/cpum_cf: correct counter number of LAST_HOST_TRANSLATIONS s390/kprobes: Fix %p uses in error messages s390/runtime instrumentation: provide uapi header file s390/sysinfo: add and display licensed internal code identifier s390/docs: reword airq section s390/docs: mention subchannel types s390/cmf: fix kerneldoc s390/eadm: fix CONFIG_BLOCK include dependency
Diffstat (limited to 'Documentation/driver-api/s390-drivers.rst')
-rw-r--r--Documentation/driver-api/s390-drivers.rst32
1 files changed, 28 insertions, 4 deletions
diff --git a/Documentation/driver-api/s390-drivers.rst b/Documentation/driver-api/s390-drivers.rst
index ecf8851d3565..30e6aa7e160b 100644
--- a/Documentation/driver-api/s390-drivers.rst
+++ b/Documentation/driver-api/s390-drivers.rst
@@ -22,9 +22,28 @@ While most I/O devices on a s390 system are typically driven through the
channel I/O mechanism described here, there are various other methods
(like the diag interface). These are out of the scope of this document.
+The s390 common I/O layer also provides access to some devices that are
+not strictly considered I/O devices. They are considered here as well,
+although they are not the focus of this document.
+
Some additional information can also be found in the kernel source under
Documentation/s390/driver-model.txt.
+The css bus
+===========
+
+The css bus contains the subchannels available on the system. They fall
+into several categories:
+
+* Standard I/O subchannels, for use by the system. They have a child
+ device on the ccw bus and are described below.
+* I/O subchannels bound to the vfio-ccw driver. See
+ Documentation/s390/vfio-ccw.txt.
+* Message subchannels. No Linux driver currently exists.
+* CHSC subchannels (at most one). The chsc subchannel driver can be used
+ to send asynchronous chsc commands.
+* eADM subchannels. Used for talking to storage class memory.
+
The ccw bus
===========
@@ -102,10 +121,15 @@ ccw group devices
Generic interfaces
==================
-Some interfaces are available to other drivers that do not necessarily
-have anything to do with the busses described above, but still are
-indirectly using basic infrastructure in the common I/O layer. One
-example is the support for adapter interrupts.
+The following section contains interfaces in use not only by drivers
+dealing with ccw devices, but drivers for various other s390 hardware
+as well.
+
+Adapter interrupts
+------------------
+
+The common I/O layer provides helper functions for dealing with adapter
+interrupts and interrupt vectors.
.. kernel-doc:: drivers/s390/cio/airq.c
:export: