diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2019-04-02 09:59:33 -0500 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-04-02 20:02:36 +0200 |
| commit | d71eb0ce109a124b0fa714832823b9452f2762cf (patch) | |
| tree | e5efa2ea879a545d3eb552a83343c91f873e7ffb | |
| parent | 5999bbe7a6ea3c62029532ec84dc06003a1fa258 (diff) | |
x86/speculation/mds: Add mds=full,nosmt cmdline option
Add the mds=full,nosmt cmdline option. This is like mds=full, but with
SMT disabled if the CPU is vulnerable.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
| -rw-r--r-- | Documentation/admin-guide/hw-vuln/mds.rst | 3 | ||||
| -rw-r--r-- | Documentation/admin-guide/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/admin-guide/hw-vuln/mds.rst b/Documentation/admin-guide/hw-vuln/mds.rst index 1de29d28903d..244ab47d1fb3 100644 --- a/Documentation/admin-guide/hw-vuln/mds.rst +++ b/Documentation/admin-guide/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/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 7325319c2c23..8f04985d3122 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2372,8 +2372,10 @@ 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 373ae1dcd301..9f252082a83b 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -221,6 +221,7 @@ 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", @@ -238,8 +239,13 @@ 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]); } @@ -255,6 +261,10 @@ 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; } |