Commit 5aa227b4 authored by Sophie Brun's avatar Sophie Brun

Import Upstream version 5.3.15

parent ec0c7b18
......@@ -486,6 +486,8 @@ What: /sys/devices/system/cpu/vulnerabilities
Date: January 2018
Contact: Linux kernel mailing list <[email protected]>
Description: Information about CPU vulnerabilities
......@@ -12,3 +12,5 @@ are configurable at compile, boot or run time.
......@@ -265,8 +265,11 @@ time with the option "mds=". The valid arguments for this option are:
============ =============================================================
Not specifying this option is equivalent to "mds=full".
Not specifying this option is equivalent to "mds=full". For processors
that are affected by both TAA (TSX Asynchronous Abort) and MDS,
specifying just "mds=off" without an accompanying "tsx_async_abort=off"
will have no effect as the same mitigation is used for both
Mitigation selection guide
iTLB multihit
iTLB multihit is an erratum where some processors may incur a machine check
error, possibly resulting in an unrecoverable CPU lockup, when an
instruction fetch hits multiple entries in the instruction TLB. This can
occur when the page size is changed along with either the physical address
or cache type. A malicious guest running on a virtualized system can
exploit this erratum to perform a denial of service attack.
Affected processors
Variations of this erratum are present on most Intel Core and Xeon processor
models. The erratum is not present on:
- non-Intel processors
- Some Atoms (Airmont, Bonnell, Goldmont, GoldmontPlus, Saltwell, Silvermont)
- Intel processors that have the PSCHANGE_MC_NO bit set in the
Related CVEs
The following CVE entry is related to this issue:
============== =================================================
CVE-2018-12207 Machine Check Error Avoidance on Page Size Change
============== =================================================
Privileged software, including OS and virtual machine managers (VMM), are in
charge of memory management. A key component in memory management is the control
of the page tables. Modern processors use virtual memory, a technique that creates
the illusion of a very large memory for processors. This virtual space is split
into pages of a given size. Page tables translate virtual addresses to physical
To reduce latency when performing a virtual to physical address translation,
processors include a structure, called TLB, that caches recent translations.
There are separate TLBs for instruction (iTLB) and data (dTLB).
Under this errata, instructions are fetched from a linear address translated
using a 4 KB translation cached in the iTLB. Privileged software modifies the
paging structure so that the same linear address using large page size (2 MB, 4
MB, 1 GB) with a different physical address or memory type. After the page
structure modification but before the software invalidates any iTLB entries for
the linear address, a code fetch that happens on the same linear address may
cause a machine-check error which can result in a system hang or shutdown.
Attack scenarios
Attacks against the iTLB multihit erratum can be mounted from malicious
guests in a virtualized system.
iTLB multihit system information
The Linux kernel provides a sysfs interface to enumerate the current iTLB
multihit status of the system:whether the system is vulnerable and which
mitigations are active. The relevant sysfs file is:
The possible values in this file are:
.. list-table::
* - Not affected
- The processor is not vulnerable.
* - KVM: Mitigation: Split huge pages
- Software changes mitigate this issue.
* - KVM: Vulnerable
- The processor is vulnerable, but no mitigation enabled
Enumeration of the erratum
A new bit has been allocated in the IA32_ARCH_CAPABILITIES (PSCHANGE_MC_NO) msr
and will be set on CPU's which are mitigated against this issue.
======================================= =========== ===============================
IA32_ARCH_CAPABILITIES MSR Not present Possibly vulnerable,check model
IA32_ARCH_CAPABILITIES[PSCHANGE_MC_NO] '0' Likely vulnerable,check model
======================================= =========== ===============================
Mitigation mechanism
This erratum can be mitigated by restricting the use of large page sizes to
non-executable pages. This forces all iTLB entries to be 4K, and removes
the possibility of multiple hits.
In order to mitigate the vulnerability, KVM initially marks all huge pages
as non-executable. If the guest attempts to execute in one of those pages,
the page is broken down into 4K pages, which are then marked executable.
If EPT is disabled or not available on the host, KVM is in control of TLB
flushes and the problematic situation cannot happen. However, the shadow
EPT paging mechanism used by nested virtualization is vulnerable, because
the nested guest can trigger multiple iTLB hits by modifying its own
(non-nested) page tables. For simplicity, KVM will make large pages
non-executable in all shadow paging modes.
Mitigation control on the kernel command line and KVM - module parameter
The KVM hypervisor mitigation mechanism for marking huge pages as
non-executable can be controlled with a module parameter "nx_huge_pages=".
The kernel command line allows to control the iTLB multihit mitigations at
boot time with the option "kvm.nx_huge_pages=".
The valid arguments for these options are:
========== ================================================================
force Mitigation is enabled. In this case, the mitigation implements
non-executable huge pages in Linux kernel KVM module. All huge
pages in the EPT are marked as non-executable.
If a guest attempts to execute in one of those pages, the page is
broken down into 4K pages, which are then marked executable.
off Mitigation is disabled.
auto Enable mitigation only if the platform is affected and the kernel
was not booted with the "mitigations=off" command line parameter.
This is the default option.
========== ================================================================
Mitigation selection guide
1. No virtualization in use
The system is protected by the kernel unconditionally and no further
action is required.
2. Virtualization with trusted guests
If the guest comes from a trusted source, you may assume that the guest will
not attempt to maliciously exploit these errata and no further action is
3. Virtualization with untrusted guests
If the guest comes from an untrusted source, the guest host kernel will need
to apply iTLB multihit mitigation via the kernel command line or kvm
module parameter.
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......@@ -2040,6 +2040,25 @@
KVM MMU at runtime.
Default is 0 (off)
[KVM] Controls the software workaround for the
force : Always deploy workaround.
off : Never deploy workaround.
auto : Deploy workaround based on the presence of
Default is 'auto'.
If the software workaround is enabled for the host,
guests do need not to enable it for nested guests.
[KVM] Controls how many 4KiB pages are periodically zapped
back to huge pages. 0 disables the recovery, otherwise if
the value is N KVM will zap 1/Nth of the 4KiB pages every
minute. The default is 60.
kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Default is 1 (enabled)
......@@ -2430,6 +2449,12 @@
SMT on vulnerable CPUs
off - Unconditionally disable MDS mitigation
On TAA-affected machines, mds=off can be prevented by
an active TAA mitigation as both vulnerabilities are
mitigated with the same mechanism so in order to disable
this mitigation, you need to specify tsx_async_abort=off
Not specifying this option is equivalent to
......@@ -2612,6 +2637,13 @@
ssbd=force-off [ARM64]
l1tf=off [X86]
mds=off [X86]
tsx_async_abort=off [X86]
kvm.nx_huge_pages=off [X86]
This does not have any effect on
kvm.nx_huge_pages when
auto (default)
Mitigate all CPU vulnerabilities, but leave SMT
......@@ -2627,6 +2659,7 @@
be fully mitigated, even if it means losing SMT.
Equivalent to: l1tf=flush,nosmt [X86]
mds=full,nosmt [X86]
tsx_async_abort=full,nosmt [X86]
......@@ -4813,6 +4846,76 @@
interruptions from clocksource watchdog are not
tsx= [X86] Control Transactional Synchronization
Extensions (TSX) feature in Intel processors that
support TSX control.
This parameter controls the TSX feature. The options are:
on - Enable TSX on the system. Although there are
mitigations for all known security vulnerabilities,
TSX has been known to be an accelerator for
several previous speculation-related CVEs, and
so there may be unknown security risks associated
with leaving it enabled.
off - Disable TSX on the system. (Note that this
option takes effect only on newer CPUs which are
not vulnerable to MDS, i.e., have
the new IA32_TSX_CTRL MSR through a microcode
update. This new MSR allows for the reliable
deactivation of the TSX functionality.)
auto - Disable TSX if X86_BUG_TAA is present,
otherwise enable TSX on the system.
Not specifying this option is equivalent to tsx=off.
See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
for more details.
tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
Abort (TAA) vulnerability.
Similar to Micro-architectural Data Sampling (MDS)
certain CPUs that support Transactional
Synchronization Extensions (TSX) are vulnerable to an
exploit against CPU internal buffers which can forward
information to a disclosure gadget under certain
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
This parameter controls the TAA mitigation. The
options are:
full - Enable TAA mitigation on vulnerable CPUs
if TSX is enabled.
full,nosmt - Enable TAA mitigation and disable SMT on
vulnerable CPUs. If TSX is disabled, SMT
is not disabled because CPU is not
vulnerable to cross-thread TAA attacks.
off - Unconditionally disable TAA mitigation
On MDS-affected machines, tsx_async_abort=off can be
prevented by an active MDS mitigation as both vulnerabilities
are mitigated with the same mechanism so in order to disable
this mitigation, you need to specify mds=off too.
Not specifying this option is equivalent to
tsx_async_abort=full. On CPUs which are MDS affected
and deploy MDS mitigation, TAA mitigation is not
required and doesn't provide any additional
For details see:
Documentation/admin-guide/hw-vuln/tsx_async_abort.rst[2|3]= [HW,JOY]
TurboGraFX parallel port interface
......@@ -91,6 +91,11 @@ stable kernels.
| ARM | MMU-500 | #841119,826419 | N/A |
| Broadcom | Brahma-B53 | N/A | ARM64_ERRATUM_845719 |
| Broadcom | Brahma-B53 | N/A | ARM64_ERRATUM_843419 |
| Cavium | ThunderX ITS | #22375,24313 | CAVIUM_ERRATUM_22375 |
| Cavium | ThunderX ITS | #23144 | CAVIUM_ERRATUM_23144 |
......@@ -124,7 +129,7 @@ stable kernels.
| Qualcomm Tech. | Kryo/Falkor v1 | E1003 | QCOM_FALKOR_ERRATUM_1003 |
| Qualcomm Tech. | Falkor v1 | E1009 | QCOM_FALKOR_ERRATUM_1009 |
| Qualcomm Tech. | Kryo/Falkor v1 | E1009 | QCOM_FALKOR_ERRATUM_1009 |
| Qualcomm Tech. | QDF2400 ITS | E0065 | QCOM_QDF2400_ERRATUM_0065 |
......@@ -81,6 +81,12 @@ Optional properties:
Definition: Name of external front end module used. Some valid FEM names
for example: "microsemi-lx5586", "sky85703-11"
and "sky85803" etc.
- qcom,snoc-host-cap-8bit-quirk:
Usage: Optional
Value type: <empty>
Definition: Quirk specifying that the firmware expects the 8bit version
of the host capability QMI request
Example (to supply PCI based wifi block details):
......@@ -27,6 +27,7 @@ x86-specific Documentation
.. SPDX-License-Identifier: GPL-2.0
TSX Async Abort (TAA) mitigation
.. _tsx_async_abort:
TSX Async Abort (TAA) is a side channel attack on internal buffers in some
Intel processors similar to Microachitectural Data Sampling (MDS). In this
case certain loads may speculatively pass invalid data to dependent operations
when an asynchronous abort condition is pending in a Transactional
Synchronization Extensions (TSX) transaction. This includes loads with no
fault or assist condition. Such loads may speculatively expose stale data from
the same uarch data structures as in MDS, with same scope of exposure i.e.
same-thread and cross-thread. This issue affects all current processors that
support TSX.
Mitigation strategy
a) TSX disable - one of the mitigations is to disable TSX. A new MSR
IA32_TSX_CTRL will be available in future and current processors after
microcode update which can be used to disable TSX. In addition, it
controls the enumeration of the TSX feature bits (RTM and HLE) in CPUID.
b) Clear CPU buffers - similar to MDS, clearing the CPU buffers mitigates this
vulnerability. More details on this approach can be found in