Merge remote-tracking branch 'fslc/4.14-2.0.x-imx' into toradex_4.14-2.0.x-imx-next

14 files changed, 685 insertions, 37 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 6cae60929cb6..645687b1870d 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -380,6 +380,7 @@ What:		/sys/devices/system/cpu/vulnerabilities
 		/sys/devices/system/cpu/vulnerabilities/spectre_v2
 		/sys/devices/system/cpu/vulnerabilities/spec_store_bypass
 		/sys/devices/system/cpu/vulnerabilities/l1tf
+		/sys/devices/system/cpu/vulnerabilities/mds
 Date:		January 2018
 Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
 Description:	Information about CPU vulnerabilities
@@ -392,8 +393,7 @@ Description:	Information about CPU vulnerabilities
 		"Vulnerable"	  CPU is affected and no mitigation in effect
 		"Mitigation: $M"  CPU is affected and mitigation $M is in effect
 
-		Details about the l1tf file can be found in
-		Documentation/admin-guide/l1tf.rst
+		See also: Documentation/admin-guide/hw-vuln/index.rst
 
 What:		/sys/devices/system/cpu/smt
 		/sys/devices/system/cpu/smt/active
diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst
new file mode 100644
index 000000000000..ffc064c1ec68
--- /dev/null
+++ b/Documentation/admin-guide/hw-vuln/index.rst
@@ -0,0 +1,13 @@
+========================
+Hardware vulnerabilities
+========================
+
+This section describes CPU vulnerabilities and provides an overview of the
+possible mitigations along with guidance for selecting mitigations if they
+are configurable at compile, boot or run time.
+
+.. toctree::
+   :maxdepth: 1
+
+   l1tf
+   mds
diff --git a/Documentation/admin-guide/l1tf.rst b/Documentation/admin-guide/hw-vuln/l1tf.rst
index 9f5924f81f89..31653a9f0e1b 100644
--- a/Documentation/admin-guide/l1tf.rst
+++ b/Documentation/admin-guide/hw-vuln/l1tf.rst
@@ -445,6 +445,7 @@ The default is 'cond'. If 'l1tf=full,force' is given on the kernel command
 line, then 'always' is enforced and the kvm-intel.vmentry_l1d_flush
 module parameter is ignored and writes to the sysfs file are rejected.
 
+.. _mitigation_selection:
 
 Mitigation selection guide
 --------------------------
@@ -556,7 +557,7 @@ When nested virtualization is in use, three operating systems are involved:
 the bare metal hypervisor, the nested hypervisor and the nested virtual
 machine.  VMENTER operations from the nested hypervisor into the nested
 guest will always be processed by the bare metal hypervisor. If KVM is the
-bare metal hypervisor it wiil:
+bare metal hypervisor it will:
 
  - Flush the L1D cache on every switch from the nested hypervisor to the
    nested virtual machine, so that the nested hypervisor's secrets are not
diff --git a/Documentation/admin-guide/hw-vuln/mds.rst b/Documentation/admin-guide/hw-vuln/mds.rst
new file mode 100644
index 000000000000..e3a796c0d3a2
--- /dev/null
+++ b/Documentation/admin-guide/hw-vuln/mds.rst
@@ -0,0 +1,308 @@
+MDS - Microarchitectural Data Sampling
+======================================
+
+Microarchitectural Data Sampling is a hardware vulnerability which allows
+unprivileged speculative access to data which is available in various CPU
+internal buffers.
+
+Affected processors
+-------------------
+
+This vulnerability affects a wide range of Intel processors. The
+vulnerability is not present on:
+
+   - Processors from AMD, Centaur and other non Intel vendors
+
+   - Older processor models, where the CPU family is < 6
+
+   - Some Atoms (Bonnell, Saltwell, Goldmont, GoldmontPlus)
+
+   - Intel processors which have the ARCH_CAP_MDS_NO bit set in the
+     IA32_ARCH_CAPABILITIES MSR.
+
+Whether a processor is affected or not can be read out from the MDS
+vulnerability file in sysfs. See :ref:`mds_sys_info`.
+
+Not all processors are affected by all variants of MDS, but the mitigation
+is identical for all of them so the kernel treats them as a single
+vulnerability.
+
+Related CVEs
+------------
+
+The following CVE entries are related to the MDS vulnerability:
+
+   ==============  =====  ===================================================
+   CVE-2018-12126  MSBDS  Microarchitectural Store Buffer Data Sampling
+   CVE-2018-12130  MFBDS  Microarchitectural Fill Buffer Data Sampling
+   CVE-2018-12127  MLPDS  Microarchitectural Load Port Data Sampling
+   CVE-2019-11091  MDSUM  Microarchitectural Data Sampling Uncacheable Memory
+   ==============  =====  ===================================================
+
+Problem
+-------
+
+When performing store, load, L1 refill operations, processors write data
+into temporary microarchitectural structures (buffers). The data in the
+buffer can be forwarded to load operations as an optimization.
+
+Under certain conditions, usually a fault/assist caused by a load
+operation, data unrelated to the load memory address can be speculatively
+forwarded from the buffers. Because the load operation causes a fault or
+assist and its result will be discarded, the forwarded data will not cause
+incorrect program execution or state changes. But a malicious operation
+may be able to forward this speculative data to a disclosure gadget which
+allows in turn to infer the value via a cache side channel attack.
+
+Because the buffers are potentially shared between Hyper-Threads cross
+Hyper-Thread attacks are possible.
+
+Deeper technical information is available in the MDS specific x86
+architecture section: :ref:`Documentation/x86/mds.rst <mds>`.
+
+
+Attack scenarios
+----------------
+
+Attacks against the MDS vulnerabilities can be mounted from malicious non
+priviledged user space applications running on hosts or guest. Malicious
+guest OSes can obviously mount attacks as well.
+
+Contrary to other speculation based vulnerabilities the MDS vulnerability
+does not allow the attacker to control the memory target address. As a
+consequence the attacks are purely sampling based, but as demonstrated with
+the TLBleed attack samples can be postprocessed successfully.
+
+Web-Browsers
+^^^^^^^^^^^^
+
+  It's unclear whether attacks through Web-Browsers are possible at
+  all. The exploitation through Java-Script is considered very unlikely,
+  but other widely used web technologies like Webassembly could possibly be
+  abused.
+
+
+.. _mds_sys_info:
+
+MDS system information
+-----------------------
+
+The Linux kernel provides a sysfs interface to enumerate the current MDS
+status of the system: whether the system is vulnerable, and which
+mitigations are active. The relevant sysfs file is:
+
+/sys/devices/system/cpu/vulnerabilities/mds
+
+The possible values in this file are:
+
+  .. list-table::
+
+     * - 'Not affected'
+       - The processor is not vulnerable
+     * - 'Vulnerable'
+       - The processor is vulnerable, but no mitigation enabled
+     * - 'Vulnerable: Clear CPU buffers attempted, no microcode'
+       - The processor is vulnerable but microcode is not updated.
+
+         The mitigation is enabled on a best effort basis. See :ref:`vmwerv`
+     * - 'Mitigation: Clear CPU buffers'
+       - The processor is vulnerable and the CPU buffer clearing mitigation is
+         enabled.
+
+If the processor is vulnerable then the following information is appended
+to the above information:
+
+    ========================  ============================================
+    'SMT vulnerable'          SMT is enabled
+    'SMT mitigated'           SMT is enabled and mitigated
+    'SMT disabled'            SMT is disabled
+    'SMT Host state unknown'  Kernel runs in a VM, Host SMT state unknown
+    ========================  ============================================
+
+.. _vmwerv:
+
+Best effort mitigation mode
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+  If the processor is vulnerable, but the availability of the microcode based
+  mitigation mechanism is not advertised via CPUID the kernel selects a best
+  effort mitigation mode.  This mode invokes the mitigation instructions
+  without a guarantee that they clear the CPU buffers.
+
+  This is done to address virtualization scenarios where the host has the
+  microcode update applied, but the hypervisor is not yet updated to expose
+  the CPUID to the guest. If the host has updated microcode the protection
+  takes effect otherwise a few cpu cycles are wasted pointlessly.
+
+  The state in the mds sysfs file reflects this situation accordingly.
+
+
+Mitigation mechanism
+-------------------------
+
+The kernel detects the affected CPUs and the presence of the microcode
+which is required.
+
+If a CPU is affected and the microcode is available, then the kernel
+enables the mitigation by default. The mitigation can be controlled at boot
+time via a kernel command line option. See
+:ref:`mds_mitigation_control_command_line`.
+
+.. _cpu_buffer_clear:
+
+CPU buffer clearing
+^^^^^^^^^^^^^^^^^^^
+
+  The mitigation for MDS clears the affected CPU buffers on return to user
+  space and when entering a guest.
+
+  If SMT is enabled it also clears the buffers on idle entry when the CPU
+  is only affected by MSBDS and not any other MDS variant, because the
+  other variants cannot be protected against cross Hyper-Thread attacks.
+
+  For CPUs which are only affected by MSBDS the user space, guest and idle
+  transition mitigations are sufficient and SMT is not affected.
+
+.. _virt_mechanism:
+
+Virtualization mitigation
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+  The protection for host to guest transition depends on the L1TF
+  vulnerability of the CPU:
+
+  - CPU is affected by L1TF:
+
+    If the L1D flush mitigation is enabled and up to date microcode is
+    available, the L1D flush mitigation is automatically protecting the
+    guest transition.
+
+    If the L1D flush mitigation is disabled then the MDS mitigation is
+    invoked explicit when the host MDS mitigation is enabled.
+
+    For details on L1TF and virtualization see:
+    :ref:`Documentation/admin-guide/hw-vuln//l1tf.rst <mitigation_control_kvm>`.
+
+  - CPU is not affected by L1TF:
+
+    CPU buffers are flushed before entering the guest when the host MDS
+    mitigation is enabled.
+
+  The resulting MDS protection matrix for the host to guest transition:
+
+  ============ ===== ============= ============ =================
+   L1TF         MDS   VMX-L1FLUSH   Host MDS     MDS-State
+
+   Don't care   No    Don't care    N/A          Not affected
+
+   Yes          Yes   Disabled      Off          Vulnerable
+
+   Yes          Yes   Disabled      Full         Mitigated
+
+   Yes          Yes   Enabled       Don't care   Mitigated
+
+   No           Yes   N/A           Off          Vulnerable
+
+   No           Yes   N/A           Full         Mitigated
+  ============ ===== ============= ============ =================
+
+  This only covers the host to guest transition, i.e. prevents leakage from
+  host to guest, but does not protect the guest internally. Guests need to
+  have their own protections.
+
+.. _xeon_phi:
+
+XEON PHI specific considerations
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+  The XEON PHI processor family is affected by MSBDS which can be exploited
+  cross Hyper-Threads when entering idle states. Some XEON PHI variants allow
+  to use MWAIT in user space (Ring 3) which opens an potential attack vector
+  for malicious user space. The exposure can be disabled on the kernel
+  command line with the 'ring3mwait=disable' command line option.
+
+  XEON PHI is not affected by the other MDS variants and MSBDS is mitigated
+  before the CPU enters a idle state. As XEON PHI is not affected by L1TF
+  either disabling SMT is not required for full protection.
+
+.. _mds_smt_control:
+
+SMT control
+^^^^^^^^^^^
+
+  All MDS variants except MSBDS can be attacked cross Hyper-Threads. That
+  means on CPUs which are affected by MFBDS or MLPDS it is necessary to
+  disable SMT for full protection. These are most of the affected CPUs; the
+  exception is XEON PHI, see :ref:`xeon_phi`.
+
+  Disabling SMT can have a significant performance impact, but the impact
+  depends on the type of workloads.
+
+  See the relevant chapter in the L1TF mitigation documentation for details:
+  :ref:`Documentation/admin-guide/hw-vuln/l1tf.rst <smt_control>`.
+
+
+.. _mds_mitigation_control_command_line:
+
+Mitigation control on the kernel command line
+---------------------------------------------
+
+The kernel command line allows to control the MDS mitigations at boot
+time with the option "mds=". The valid arguments for this option are:
+
+  ============  =============================================================
+  full		If the CPU is vulnerable, enable all available mitigations
+		for the MDS vulnerability, CPU buffer clearing on exit to
+		userspace and when entering a VM. Idle transitions are
+		protected as well if SMT is enabled.
+
+		It does not automatically disable SMT.
+
+  full,nosmt	The same as mds=full, with SMT disabled on vulnerable
+		CPUs.  This is the complete mitigation.
+
+  off		Disables MDS mitigations completely.
+
+  ============  =============================================================
+
+Not specifying this option is equivalent to "mds=full".
+
+
+Mitigation selection guide
+--------------------------
+
+1. Trusted userspace
+^^^^^^^^^^^^^^^^^^^^
+
+   If all userspace applications are from a trusted source and do not
+   execute untrusted code which is supplied externally, then the mitigation
+   can be disabled.
+
+
+2. Virtualization with trusted guests
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+   The same considerations as above versus trusted user space apply.
+
+3. Virtualization with untrusted guests
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+   The protection depends on the state of the L1TF mitigations.
+   See :ref:`virt_mechanism`.
+
+   If the MDS mitigation is enabled and SMT is disabled, guest to host and
+   guest to guest attacks are prevented.
+
+.. _mds_default_mitigations:
+
+Default mitigations
+-------------------
+
+  The kernel default mitigations for vulnerable processors are:
+
+  - Enable CPU buffer clearing
+
+  The kernel does not by default enforce the disabling of SMT, which leaves
+  SMT systems vulnerable when running untrusted code. The same rationale as
+  for L1TF applies.
+  See :ref:`Documentation/admin-guide/hw-vuln//l1tf.rst <default_mitigations>`.
diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst
index 78f8f00c369f..f8d4e9af01dc 100644
--- a/Documentation/admin-guide/index.rst
+++ b/Documentation/admin-guide/index.rst
@@ -17,14 +17,12 @@ etc.
    kernel-parameters
    devices
 
-This section describes CPU vulnerabilities and provides an overview of the
-possible mitigations along with guidance for selecting mitigations if they
-are configurable at compile, boot or run time.
+This section describes CPU vulnerabilities and their mitigations.
 
 .. toctree::
    :maxdepth: 1
 
-   l1tf
+   hw-vuln/index
 
 Here is a set of documents aimed at users who are trying to track down
 problems and bugs in particular.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 94fa46d2d805..9240b2caa0b1 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1971,7 +1971,7 @@
 
 			Default is 'flush'.
 
-			For details see: Documentation/admin-guide/l1tf.rst
+			For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
 
 	l2cr=		[PPC]
 
@@ -2214,6 +2214,32 @@
 			Format: <first>,<last>
 			Specifies range of consoles to be captured by the MDA.
 
+	mds=		[X86,INTEL]
+			Control mitigation for the Micro-architectural Data
+			Sampling (MDS) vulnerability.
+
+			Certain CPUs are vulnerable to an exploit against CPU
+			internal buffers which can forward information to a
+			disclosure gadget under certain conditions.
+
+			In vulnerable processors, the speculatively
+			forwarded data can be used in a cache side channel
+			attack, to access data to which the attacker does
+			not have direct access.
+
+			This parameter controls the MDS mitigation. The
+			options are:
+
+			full       - Enable MDS mitigation on vulnerable CPUs
+			full,nosmt - Enable MDS mitigation and disable
+				     SMT on vulnerable CPUs
+			off        - Unconditionally disable MDS mitigation
+
+			Not specifying this option is equivalent to
+			mds=full.
+
+			For details see: Documentation/admin-guide/hw-vuln/mds.rst
+
 	mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
 			Amount of memory to be used when the kernel is not able
 			to see the whole system memory or for test.
@@ -2362,6 +2388,40 @@
 			in the "bleeding edge" mini2440 support kernel at
 			http://repo.or.cz/w/linux-2.6/mini2440.git
 
+	mitigations=
+			[X86,PPC,S390] Control optional mitigations for CPU
+			vulnerabilities.  This is a set of curated,
+			arch-independent options, each of which is an
+			aggregation of existing arch-specific options.
+
+			off
+				Disable all optional CPU mitigations.  This
+				improves system performance, but it may also
+				expose users to several CPU vulnerabilities.
+				Equivalent to: nopti [X86,PPC]
+					       nospectre_v1 [PPC]
+					       nobp=0 [S390]
+					       nospectre_v2 [X86,PPC,S390]
+					       spectre_v2_user=off [X86]
+					       spec_store_bypass_disable=off [X86,PPC]
+					       l1tf=off [X86]
+					       mds=off [X86]
+
+			auto (default)
+				Mitigate all CPU vulnerabilities, but leave SMT
+				enabled, even if it's vulnerable.  This is for
+				users who don't want to be surprised by SMT
+				getting disabled across kernel upgrades, or who
+				have other ways of avoiding SMT-based attacks.
+				Equivalent to: (default behavior)
+
+			auto,nosmt
+				Mitigate all CPU vulnerabilities, disabling SMT
+				if needed.  This is for users who always want to
+				be fully mitigated, even if it means losing SMT.
+				Equivalent to: l1tf=flush,nosmt [X86]
+					       mds=full,nosmt [X86]
+
 	mminit_loglevel=
 			[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
 			parameter allows control of the logging verbosity for
diff --git a/Documentation/conf.py b/Documentation/conf.py
index 63857d33778c..329c519158b6 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py
@@ -37,7 +37,7 @@ needs_sphinx = '1.3'
 extensions = ['kerneldoc', 'rstFlatTable', 'kernel_include', 'cdomain', 'kfigure']
 
 # The name of the math extension changed on Sphinx 1.4
-if major == 1 and minor > 3:
+if (major == 1 and minor > 3) or (major > 1):
     extensions.append("sphinx.ext.imgmath")
 else:
     extensions.append("sphinx.ext.pngmath")
diff --git a/Documentation/index.rst b/Documentation/index.rst
index cb7f1ba5b3b1..ccfebc260e04 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -86,6 +86,7 @@ implementation.
    :maxdepth: 2
 
    sh/index
+   x86/index
 
 Korean translations
 -------------------
diff --git a/Documentation/sphinx/kerneldoc.py b/Documentation/sphinx/kerneldoc.py
index fbedcc39460b..0bae1193fc05 100644
--- a/Documentation/sphinx/kerneldoc.py
+++ b/Documentation/sphinx/kerneldoc.py
@@ -37,7 +37,19 @@ import glob
 from docutils import nodes, statemachine
 from docutils.statemachine import ViewList
 from docutils.parsers.rst import directives, Directive
-from sphinx.ext.autodoc import AutodocReporter
+
+#
+# AutodocReporter is only good up to Sphinx 1.7
+#
+import sphinx
+
+Use_SSI = sphinx.__version__[:3] >= '1.7'
+if Use_SSI:
+    from sphinx.util.docutils import switch_source_input
+else:
+    from sphinx.ext.autodoc import AutodocReporter
+
+import kernellog
 
 __version__  = '1.0'
 
@@ -86,7 +98,8 @@ class KernelDocDirective(Directive):
         cmd += [filename]
 
         try:
-            env.app.verbose('calling kernel-doc \'%s\'' % (" ".join(cmd)))
+            kernellog.verbose(env.app,
+                              'calling kernel-doc \'%s\'' % (" ".join(cmd)))
 
             p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             out, err = p.communicate()
@@ -96,7 +109,8 @@ class KernelDocDirective(Directive):
             if p.returncode != 0:
                 sys.stderr.write(err)
 
-                env.app.warn('kernel-doc \'%s\' failed with return code %d' % (" ".join(cmd), p.returncode))
+                kernellog.warn(env.app,
+                               'kernel-doc \'%s\' failed with return code %d' % (" ".join(cmd), p.returncode))
                 return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
             elif env.config.kerneldoc_verbosity > 0:
                 sys.stderr.write(err)
@@ -117,20 +131,28 @@ class KernelDocDirective(Directive):
                     lineoffset += 1
 
             node = nodes.section()
-            buf = self.state.memo.title_styles, self.state.memo.section_level, self.state.memo.reporter
+            self.do_parse(result, node)
+
+            return node.children
+
+        except Exception as e:  # pylint: disable=W0703
+            kernellog.warn(env.app, 'kernel-doc \'%s\' processing failed with: %s' %
+                           (" ".join(cmd), str(e)))
+            return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
+
+    def do_parse(self, result, node):
+        if Use_SSI:
+            with switch_source_input(self.state, result):
+                self.state.nested_parse(result, 0, node, match_titles=1)
+        else:
+            save = self.state.memo.title_styles, self.state.memo.section_level, self.state.memo.reporter
             self.state.memo.reporter = AutodocReporter(result, self.state.memo.reporter)
             self.state.memo.title_styles, self.state.memo.section_level = [], 0
             try:
                 self.state.nested_parse(result, 0, node, match_titles=1)
             finally:
-                self.state.memo.title_styles, self.state.memo.section_level, self.state.memo.reporter = buf
+                self.state.memo.title_styles, self.state.memo.section_level, self.state.memo.reporter = save
 
-            return node.children
-
-        except Exception as e:  # pylint: disable=W0703
-            env.app.warn('kernel-doc \'%s\' processing failed with: %s' %
-                         (" ".join(cmd), str(e)))
-            return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
 
 def setup(app):
     app.add_config_value('kerneldoc_bin', None, 'env')
diff --git a/Documentation/sphinx/kernellog.py b/Documentation/sphinx/kernellog.py
new file mode 100644
index 000000000000..af924f51a7dc
--- /dev/null
+++ b/Documentation/sphinx/kernellog.py
@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Sphinx has deprecated its older logging interface, but the replacement
+# only goes back to 1.6.  So here's a wrapper layer to keep around for
+# as long as we support 1.4.
+#
+import sphinx
+
+if sphinx.__version__[:3] >= '1.6':
+    UseLogging = True
+    from sphinx.util import logging
+    logger = logging.getLogger('kerneldoc')
+else:
+    UseLogging = False
+
+def warn(app, message):
+    if UseLogging:
+        logger.warning(message)
+    else:
+        app.warn(message)
+
+def verbose(app, message):
+    if UseLogging:
+        logger.verbose(message)
+    else:
+        app.verbose(message)
+
+
diff --git a/Documentation/sphinx/kfigure.py b/Documentation/sphinx/kfigure.py
index cef4ad19624c..4770cadbee0a 100644
--- a/Documentation/sphinx/kfigure.py
+++ b/Documentation/sphinx/kfigure.py
@@ -60,6 +60,8 @@ import sphinx
 from sphinx.util.nodes import clean_astext
 from six import iteritems
 
+import kernellog
+
 PY3 = sys.version_info[0] == 3
 
 if PY3:
@@ -171,20 +173,20 @@ def setupTools(app):
     This function is called once, when the builder is initiated.
     """
     global dot_cmd, convert_cmd   # pylint: disable=W0603
-    app.verbose("kfigure: check installed tools ...")
+    kernellog.verbose(app, "kfigure: check installed tools ...")
 
     dot_cmd = which('dot')
     convert_cmd = which('convert')
 
     if dot_cmd:
-        app.verbose("use dot(1) from: " + dot_cmd)
+        kernellog.verbose(app, "use dot(1) from: " + dot_cmd)
     else:
-        app.warn("dot(1) not found, for better output quality install "
-                 "graphviz from http://www.graphviz.org")
+        kernellog.warn(app, "dot(1) not found, for better output quality install "
+                       "graphviz from http://www.graphviz.org")
     if convert_cmd:
-        app.verbose("use convert(1) from: " + convert_cmd)
+        kernellog.verbose(app, "use convert(1) from: " + convert_cmd)
     else:
-        app.warn(
+        kernellog.warn(app,
             "convert(1) not found, for SVG to PDF conversion install "
             "ImageMagick (https://www.imagemagick.org)")
 
@@ -220,12 +222,13 @@ def convert_image(img_node, translator, src_fname=None):
 
     # in kernel builds, use 'make SPHINXOPTS=-v' to see verbose messages
 
-    app.verbose('assert best format for: ' + img_node['uri'])
+    kernellog.verbose(app, 'assert best format for: ' + img_node['uri'])
 
     if in_ext == '.dot':
 
         if not dot_cmd:
-            app.verbose("dot from graphviz not available / include DOT raw.")
+            kernellog.verbose(app,
+                              "dot from graphviz not available / include DOT raw.")
             img_node.replace_self(file2literal(src_fname))
 
         elif translator.builder.format == 'latex':
@@ -252,7 +255,8 @@ def convert_image(img_node, translator, src_fname=None):
 
         if translator.builder.format == 'latex':
             if convert_cmd is None:
-                app.verbose("no SVG to PDF conversion available / include SVG raw.")
+                kernellog.verbose(app,
+                                  "no SVG to PDF conversion available / include SVG raw.")
                 img_node.replace_self(file2literal(src_fname))
             else:
                 dst_fname = path.join(translator.builder.outdir, fname + '.pdf')
@@ -265,18 +269,19 @@ def convert_image(img_node, translator, src_fname=None):
         _name = dst_fname[len(translator.builder.outdir) + 1:]
 
         if isNewer(dst_fname, src_fname):
-            app.verbose("convert: {out}/%s already exists and is newer" % _name)
+            kernellog.verbose(app,
+                              "convert: {out}/%s already exists and is newer" % _name)
 
         else:
             ok = False
             mkdir(path.dirname(dst_fname))
 
             if in_ext == '.dot':
-                app.verbose('convert DOT to: {out}/' + _name)
+                kernellog.verbose(app, 'convert DOT to: {out}/' + _name)
                 ok = dot2format(app, src_fname, dst_fname)
 
             elif in_ext == '.svg':
-                app.verbose('convert SVG to: {out}/' + _name)
+                kernellog.verbose(app, 'convert SVG to: {out}/' + _name)
                 ok = svg2pdf(app, src_fname, dst_fname)
 
             if not ok:
@@ -305,7 +310,8 @@ def dot2format(app, dot_fname, out_fname):
     with open(out_fname, "w") as out:
         exit_code = subprocess.call(cmd, stdout = out)
         if exit_code != 0:
-            app.warn("Error #%d when calling: %s" % (exit_code, " ".join(cmd)))
+            kernellog.warn(app,
+                          "Error #%d when calling: %s" % (exit_code, " ".join(cmd)))
     return bool(exit_code == 0)
 
 def svg2pdf(app, svg_fname, pdf_fname):
@@ -322,7 +328,7 @@ def svg2pdf(app, svg_fname, pdf_fname):
     # use stdout and stderr from parent
     exit_code = subprocess.call(cmd)
     if exit_code != 0:
-        app.warn("Error #%d when calling: %s" % (exit_code, " ".join(cmd)))
+        kernellog.warn(app, "Error #%d when calling: %s" % (exit_code, " ".join(cmd)))
     return bool(exit_code == 0)
 
 
@@ -415,15 +421,15 @@ def visit_kernel_render(self, node):
     app = self.builder.app
     srclang = node.get('srclang')
 
-    app.verbose('visit kernel-render node lang: "%s"' % (srclang))
+    kernellog.verbose('visit kernel-render node lang: "%s"' % (srclang))
 
     tmp_ext = RENDER_MARKUP_EXT.get(srclang, None)
     if tmp_ext is None:
-        app.warn('kernel-render: "%s" unknow / include raw.' % (srclang))
+        kernellog.warn('kernel-render: "%s" unknow / include raw.' % (srclang))
         return
 
     if not dot_cmd and tmp_ext == '.dot':
-        app.verbose("dot from graphviz not available / include raw.")
+        kernellog.verbose("dot from graphviz not available / include raw.")
         return
 
     literal_block = node[0]
diff --git a/Documentation/x86/conf.py b/Documentation/x86/conf.py
new file mode 100644
index 000000000000..33c5c3142e20
--- /dev/null
+++ b/Documentation/x86/conf.py
@@ -0,0 +1,10 @@
+# -*- coding: utf-8; mode: python -*-
+
+project = "X86 architecture specific documentation"
+
+tags.add("subproject")
+
+latex_documents = [
+    ('index', 'x86.tex', project,
+     'The kernel development community', 'manual'),
+]
diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
new file mode 100644
index 000000000000..ef389dcf1b1d
--- /dev/null
+++ b/Documentation/x86/index.rst
@@ -0,0 +1,8 @@
+==========================
+x86 architecture specifics
+==========================
+
+.. toctree::
+   :maxdepth: 1
+
+   mds
diff --git a/Documentation/x86/mds.rst b/Documentation/x86/mds.rst
new file mode 100644
index 000000000000..5d4330be200f
--- /dev/null
+++ b/Documentation/x86/mds.rst
@@ -0,0 +1,193 @@
+Microarchitectural Data Sampling (MDS) mitigation
+=================================================
+
+.. _mds:
+
+Overview
+--------
+
+Microarchitectural Data Sampling (MDS) is a family of side channel attacks
+on internal buffers in Intel CPUs. The variants are:
+
+ - Microarchitectural Store Buffer Data Sampling (MSBDS) (CVE-2018-12126)
+ - Microarchitectural Fill Buffer Data Sampling (MFBDS) (CVE-2018-12130)
+ - Microarchitectural Load Port Data Sampling (MLPDS) (CVE-2018-12127)
+ - Microarchitectural Data Sampling Uncacheable Memory (MDSUM) (CVE-2019-11091)
+
+MSBDS leaks Store Buffer Entries which can be speculatively forwarded to a
+dependent load (store-to-load forwarding) as an optimization. The forward
+can also happen to a faulting or assisting load operation for a different
+memory address, which can be exploited under certain conditions. Store
+buffers are partitioned between Hyper-Threads so cross thread forwarding is
+not possible. But if a thread enters or exits a sleep state the store
+buffer is repartitioned which can expose data from one thread to the other.
+
+MFBDS leaks Fill Buffer Entries. Fill buffers are used internally to manage
+L1 miss situations and to hold data which is returned or sent in response
+to a memory or I/O operation. Fill buffers can forward data to a load
+operation and also write data to the cache. When the fill buffer is
+deallocated it can retain the stale data of the preceding operations which
+can then be forwarded to a faulting or assisting load operation, which can
+be exploited under certain conditions. Fill buffers are shared between
+Hyper-Threads so cross thread leakage is possible.
+
+MLPDS leaks Load Port Data. Load ports are used to perform load operations
+from memory or I/O. The received data is then forwarded to the register
+file or a subsequent operation. In some implementations the Load Port can
+contain stale data from a previous operation which can be forwarded to
+faulting or assisting loads under certain conditions, which again can be
+exploited eventually. Load ports are shared between Hyper-Threads so cross
+thread leakage is possible.
+
+MDSUM is a special case of MSBDS, MFBDS and MLPDS. An uncacheable load from
+memory that takes a fault or assist can leave data in a microarchitectural
+structure that may later be observed using one of the same methods used by
+MSBDS, MFBDS or MLPDS.
+
+Exposure assumptions
+--------------------
+
+It is assumed that attack code resides in user space or in a guest with one
+exception. The rationale behind this assumption is that the code construct
+needed for exploiting MDS requires:
+
+ - to control the load to trigger a fault or assist
+
+ - to have a disclosure gadget which exposes the speculatively accessed
+   data for consumption through a side channel.
+
+ - to control the pointer through which the disclosure gadget exposes the
+   data
+
+The existence of such a construct in the kernel cannot be excluded with
+100% certainty, but the complexity involved makes it extremly unlikely.
+
+There is one exception, which is untrusted BPF. The functionality of
+untrusted BPF is limited, but it needs to be thoroughly investigated
+whether it can be used to create such a construct.
+
+
+Mitigation strategy
+-------------------
+
+All variants have the same mitigation strategy at least for the single CPU
+thread case (SMT off): Force the CPU to clear the affected buffers.
+
+This is achieved by using the otherwise unused and obsolete VERW
+instruction in combination with a microcode update. The microcode clears
+the affected CPU buffers when the VERW instruction is executed.
+
+For virtualization there are two ways to achieve CPU buffer
+clearing. Either the modified VERW instruction or via the L1D Flush
+command. The latter is issued when L1TF mitigation is enabled so the extra
+VERW can be avoided. If the CPU is not affected by L1TF then VERW needs to
+be issued.
+
+If the VERW instruction with the supplied segment selector argument is
+executed on a CPU without the microcode update there is no side effect
+other than a small number of pointlessly wasted CPU cycles.
+
+This does not protect against cross Hyper-Thread attacks except for MSBDS
+which is only exploitable cross Hyper-thread when one of the Hyper-Threads
+enters a C-state.
+
+The kernel provides a function to invoke the buffer clearing:
+
+    mds_clear_cpu_buffers()
+
+The mitigation is invoked on kernel/userspace, hypervisor/guest and C-state
+(idle) transitions.
+
+As a special quirk to address virtualization scenarios where the host has
+the microcode updated, but the hypervisor does not (yet) expose the
+MD_CLEAR CPUID bit to guests, the kernel issues the VERW instruction in the
+hope that it might actually clear the buffers. The state is reflected
+accordingly.
+
+According to current knowledge additional mitigations inside the kernel
+itself are not required because the necessary gadgets to expose the leaked
+data cannot be controlled in a way which allows exploitation from malicious
+user space or VM guests.
+
+Kernel internal mitigation modes
+--------------------------------
+
+ ======= ============================================================
+ off      Mitigation is disabled. Either the CPU is not affected or
+          mds=off is supplied on the kernel command line
+
+ full     Mitigation is enabled. CPU is affected and MD_CLEAR is
+          advertised in CPUID.
+
+ vmwerv	  Mitigation is enabled. CPU is affected and MD_CLEAR is not
+	  advertised in CPUID. That is mainly for virtualization
+	  scenarios where the host has the updated microcode but the
+	  hypervisor does not expose MD_CLEAR in CPUID. It's a best
+	  effort approach without guarantee.
+ ======= ============================================================
+
+If the CPU is affected and mds=off is not supplied on the kernel command
+line then the kernel selects the appropriate mitigation mode depending on
+the availability of the MD_CLEAR CPUID bit.
+
+Mitigation points
+-----------------
+
+1. Return to user space
+^^^^^^^^^^^^^^^^^^^^^^^
+
+   When transitioning from kernel to user space the CPU buffers are flushed
+   on affected CPUs when the mitigation is not disabled on the kernel
+   command line. The migitation is enabled through the static key
+   mds_user_clear.
+
+   The mitigation is invoked in prepare_exit_to_usermode() which covers
+   all but one of the kernel to user space transitions.  The exception
+   is when we return from a Non Maskable Interrupt (NMI), which is
+   handled directly in do_nmi().
+
+   (The reason that NMI is special is that prepare_exit_to_usermode() can
+    enable IRQs.  In NMI context, NMIs are blocked, and we don't want to
+    enable IRQs with NMIs blocked.)
+
+
+2. C-State transition
+^^^^^^^^^^^^^^^^^^^^^
+
+   When a CPU goes idle and enters a C-State the CPU buffers need to be
+   cleared on affected CPUs when SMT is active. This addresses the
+   repartitioning of the store buffer when one of the Hyper-Threads enters
+   a C-State.
+
+   When SMT is inactive, i.e. either the CPU does not support it or all
+   sibling threads are offline CPU buffer clearing is not required.
+
+   The idle clearing is enabled on CPUs which are only affected by MSBDS
+   and not by any other MDS variant. The other MDS variants cannot be
+   protected against cross Hyper-Thread attacks because the Fill Buffer and
+   the Load Ports are shared. So on CPUs affected by other variants, the
+   idle clearing would be a window dressing exercise and is therefore not
+   activated.
+
+   The invocation is controlled by the static key mds_idle_clear which is
+   switched depending on the chosen mitigation mode and the SMT state of
+   the system.
+
+   The buffer clear is only invoked before entering the C-State to prevent
+   that stale data from the idling CPU from spilling to the Hyper-Thread
+   sibling after the store buffer got repartitioned and all entries are
+   available to the non idle sibling.
+
+   When coming out of idle the store buffer is partitioned again so each
+   sibling has half of it available. The back from idle CPU could be then
+   speculatively exposed to contents of the sibling. The buffers are
+   flushed either on exit to user space or on VMENTER so malicious code
+   in user space or the guest cannot speculatively access them.
+
+   The mitigation is hooked into all variants of halt()/mwait(), but does
+   not cover the legacy ACPI IO-Port mechanism because the ACPI idle driver
+   has been superseded by the intel_idle driver around 2010 and is
+   preferred on all affected CPUs which are expected to gain the MD_CLEAR
+   functionality in microcode. Aside of that the IO-Port mechanism is a
+   legacy interface which is only used on older systems which are either
+   not affected or do not receive microcode updates anymore.