nobypass [PPC/POWERNV]
Disable IOMMU bypass, using IOMMU for PCI devices.
+ iommu.strict= [ARM64] Configure TLB invalidation behaviour
+ Format: { "0" | "1" }
+ 0 - Lazy mode.
+ Request that DMA unmap operations use deferred
+ invalidation of hardware TLBs, for increased
+ throughput at the cost of reduced device isolation.
+ Will fall back to strict mode if not supported by
+ the relevant IOMMU driver.
+ 1 - Strict mode (default).
+ DMA unmap operations invalidate IOMMU hardware TLBs
+ synchronously.
+
iommu.passthrough=
[ARM64] Configure DMA to bypass the IOMMU by default.
Format: { "0" | "1" }
(virtualized real and unpaged mode) on capable
Intel chips. Default is 1 (enabled)
+ kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
+ CVE-2018-3620.
+
+ Valid arguments: never, cond, always
+
+ always: L1D cache flush on every VMENTER.
+ cond: Flush L1D on VMENTER only when the code between
+ VMEXIT and VMENTER can leak host memory.
+ never: Disables the mitigation
+
+ Default is cond (do L1 cache flush in specific instances)
+
kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
feature (tagged TLBs) on capable Intel chips.
Default is 1 (enabled)
+ l1tf= [X86] Control mitigation of the L1TF vulnerability on
+ affected CPUs
+
+ The kernel PTE inversion protection is unconditionally
+ enabled and cannot be disabled.
+
+ full
+ Provides all available mitigations for the
+ L1TF vulnerability. Disables SMT and
+ enables all mitigations in the
+ hypervisors, i.e. unconditional L1D flush.
+
+ SMT control and L1D flush control via the
+ sysfs interface is still possible after
+ boot. Hypervisors will issue a warning
+ when the first VM is started in a
+ potentially insecure configuration,
+ i.e. SMT enabled or L1D flush disabled.
+
+ full,force
+ Same as 'full', but disables SMT and L1D
+ flush runtime control. Implies the
+ 'nosmt=force' command line option.
+ (i.e. sysfs control of SMT is disabled.)
+
+ flush
+ Leaves SMT enabled and enables the default
+ hypervisor mitigation, i.e. conditional
+ L1D flush.
+
+ SMT control and L1D flush control via the
+ sysfs interface is still possible after
+ boot. Hypervisors will issue a warning
+ when the first VM is started in a
+ potentially insecure configuration,
+ i.e. SMT enabled or L1D flush disabled.
+
+ flush,nosmt
+
+ Disables SMT and enables the default
+ hypervisor mitigation.
+
+ SMT control and L1D flush control via the
+ sysfs interface is still possible after
+ boot. Hypervisors will issue a warning
+ when the first VM is started in a
+ potentially insecure configuration,
+ i.e. SMT enabled or L1D flush disabled.
+
+ flush,nowarn
+ Same as 'flush', but hypervisors will not
+ warn when a VM is started in a potentially
+ insecure configuration.
+
+ off
+ Disables hypervisor mitigations and doesn't
+ emit any warnings.
+
+ Default is 'flush'.
+
+ For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
+
l2cr= [PPC]
l3cr= [PPC]
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.
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
Equivalent to smt=1.
[KNL,x86] Disable symmetric multithreading (SMT).
- nosmt=force: Force disable SMT, similar to disabling
- it in the BIOS except that some of the
- resource partitioning effects which are
- caused by having SMT enabled in the BIOS
- cannot be undone. Depending on the CPU
- type this might have a performance impact.
+ nosmt=force: Force disable SMT, cannot be undone
+ via the sysfs control file.
nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2
(indirect branch prediction) vulnerability. System may
nomsi [MSI] If the PCI_MSI kernel config parameter is
enabled, this kernel boot option can be used to
disable the use of MSI interrupts system-wide.
+ clearmsi [X86] Clears MSI/MSI-X enable bits early in boot
+ time in order to avoid issues like adapters
+ screaming irqs and preventing boot progress.
+ Also, it enforces the PCI Local Bus spec
+ rule that those bits should be 0 in system reset
+ events (useful for kexec/kdump cases).
noioapicquirk [APIC] Disable all boot interrupt quirks.
Safety option to keep boot IRQs enabled. This
should never be necessary.
spectre_v2= [X86] Control mitigation of Spectre variant 2
(indirect branch speculation) vulnerability.
+ The default operation protects the kernel from
+ user space attacks.
- on - unconditionally enable
- off - unconditionally disable
+ on - unconditionally enable, implies
+ spectre_v2_user=on
+ off - unconditionally disable, implies
+ spectre_v2_user=off
auto - kernel detects whether your CPU model is
vulnerable
CONFIG_RETPOLINE configuration option, and the
compiler with which the kernel was built.
+ Selecting 'on' will also enable the mitigation
+ against user space to user space task attacks.
+
+ Selecting 'off' will disable both the kernel and
+ the user space protections.
+
Specific mitigations can also be selected manually:
retpoline - replace indirect branches
Not specifying this option is equivalent to
spectre_v2=auto.
+ spectre_v2_user=
+ [X86] Control mitigation of Spectre variant 2
+ (indirect branch speculation) vulnerability between
+ user space tasks
+
+ on - Unconditionally enable mitigations. Is
+ enforced by spectre_v2=on
+
+ off - Unconditionally disable mitigations. Is
+ enforced by spectre_v2=off
+
+ prctl - Indirect branch speculation is enabled,
+ but mitigation can be enabled via prctl
+ per thread. The mitigation control state
+ is inherited on fork.
+
+ prctl,ibpb
+ - Like "prctl" above, but only STIBP is
+ controlled per thread. IBPB is issued
+ always when switching between different user
+ space processes.
+
+ seccomp
+ - Same as "prctl" above, but all seccomp
+ threads will enable the mitigation unless
+ they explicitly opt out.
+
+ seccomp,ibpb
+ - Like "seccomp" above, but only STIBP is
+ controlled per thread. IBPB is issued
+ always when switching between different
+ user space processes.
+
+ auto - Kernel selects the mitigation depending on
+ the available CPU features and vulnerability.
+
+ Default mitigation:
+ If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
+
+ Not specifying this option is equivalent to
+ spectre_v2_user=auto.
+
spec_store_bypass_disable=
[HW] Control Speculative Store Bypass (SSB) Disable mitigation
(Speculative Store Bypass vulnerability)
expediting. Set to zero to disable automatic
expediting.
+ ssbd= [ARM64,HW]
+ Speculative Store Bypass Disable control
+
+ On CPUs that are vulnerable to the Speculative
+ Store Bypass vulnerability and offer a
+ firmware based mitigation, this parameter
+ indicates how the mitigation should be used:
+
+ force-on: Unconditionally enable mitigation for
+ for both kernel and userspace
+ force-off: Unconditionally disable mitigation for
+ for both kernel and userspace
+ kernel: Always enable mitigation in the
+ kernel, and offer a prctl interface
+ to allow userspace to register its
+ interest in being mitigated too.
+
stack_guard_gap= [MM]
override the default stack gap protection. The value
is in page units and it defines how many pages prior
prevent spurious wakeup);
n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
pause after every control message);
+ o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
+ delay after resetting its port);
Example: quirks=0781:5580:bk,0a5c:5834:gij
usbhid.mousepoll=
projects / mirror_ubuntu-bionic-kernel.git / blobdiff