diff options
| -rw-r--r-- | Documentation/hw-vuln/mds.rst | 3 | ||||
| -rw-r--r-- | Documentation/kernel-parameters.txt | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 10 |
3 files changed, 17 insertions, 2 deletions
diff --git a/Documentation/hw-vuln/mds.rst b/Documentation/hw-vuln/mds.rst index ff6bfdb97eee..aec9e49256b5 100644 --- a/Documentation/hw-vuln/mds.rst +++ b/Documentation/hw-vuln/mds.rst @@ -260,6 +260,9 @@ time with the option "mds=". The valid arguments for this option are: 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. ============ ============================================================= diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 7164790b82c0..4c134700c120 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2341,8 +2341,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. This parameter controls the MDS mitigation. The options are: - full - Enable MDS mitigation on vulnerable CPUs - off - Unconditionally disable MDS mitigation + 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. diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index e0c77a46c55a..a8bef0a24390 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -218,6 +218,7 @@ static void x86_amd_ssb_disable(void) /* Default mitigation for L1TF-affected CPUs */ static enum mds_mitigations mds_mitigation __ro_after_init = MDS_MITIGATION_FULL; +static bool mds_nosmt __ro_after_init = false; static const char * const mds_strings[] = { [MDS_MITIGATION_OFF] = "Vulnerable", @@ -235,8 +236,13 @@ static void __init mds_select_mitigation(void) if (mds_mitigation == MDS_MITIGATION_FULL) { if (!boot_cpu_has(X86_FEATURE_MD_CLEAR)) mds_mitigation = MDS_MITIGATION_VMWERV; + static_branch_enable(&mds_user_clear); + + if (mds_nosmt && !boot_cpu_has(X86_BUG_MSBDS_ONLY)) + cpu_smt_disable(false); } + pr_info("%s\n", mds_strings[mds_mitigation]); } @@ -252,6 +258,10 @@ static int __init mds_cmdline(char *str) mds_mitigation = MDS_MITIGATION_OFF; else if (!strcmp(str, "full")) mds_mitigation = MDS_MITIGATION_FULL; + else if (!strcmp(str, "full,nosmt")) { + mds_mitigation = MDS_MITIGATION_FULL; + mds_nosmt = true; + } return 0; } |