diff options
Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
-rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 67 |
1 files changed, 65 insertions, 2 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0c404cda531a..a29301d6e6c6 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2073,10 +2073,13 @@ off Disables hypervisor mitigations and doesn't emit any warnings. + It also drops the swap size and available + RAM limit restriction on both hypervisor and + bare metal. Default is 'flush'. - For details see: Documentation/admin-guide/l1tf.rst + For details see: Documentation/admin-guide/hw-vuln/l1tf.rst l2cr= [PPC] @@ -2316,6 +2319,32 @@ 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. @@ -2473,6 +2502,40 @@ 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 @@ -2802,7 +2865,7 @@ check bypass). With this option data leaks are possible in the system. - nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2 + nospectre_v2 [X86,PPC_FSL_BOOK3E] Disable all mitigations for the Spectre variant 2 (indirect branch prediction) vulnerability. System may allow data leaks with this option, which is equivalent to spectre_v2=off. |