6.14-stable review patch. If anyone has any objections, please let me know.
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From: Pawan Gupta pawan.kumar.gupta@linux.intel.com
commit facd226f7e0c8ca936ac114aba43cb3e8b94e41e upstream.
When retpoline mitigation is enabled for spectre-v2, enabling call-depth-tracking and RSB stuffing also mitigates ITS. Add cmdline option indirect_target_selection=stuff to allow enabling RSB stuffing mitigation.
When retpoline mitigation is not enabled, =stuff option is ignored, and default mitigation for ITS is deployed.
Signed-off-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Reviewed-by: Josh Poimboeuf jpoimboe@kernel.org Reviewed-by: Alexandre Chartre alexandre.chartre@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- Documentation/admin-guide/kernel-parameters.txt | 3 +++ arch/x86/kernel/cpu/bugs.c | 19 +++++++++++++++++++ 2 files changed, 22 insertions(+)
--- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2188,6 +2188,9 @@ mitigation. vmexit: Only deploy mitigation if CPU is affected by guest/host isolation part of ITS. + stuff: Deploy RSB-fill mitigation when retpoline is + also deployed. Otherwise, deploy the default + mitigation.
For details see: Documentation/admin-guide/hw-vuln/indirect-target-selection.rst --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1190,6 +1190,7 @@ enum its_mitigation_cmd { ITS_CMD_OFF, ITS_CMD_ON, ITS_CMD_VMEXIT, + ITS_CMD_RSB_STUFF, };
enum its_mitigation { @@ -1230,6 +1231,8 @@ static int __init its_parse_cmdline(char setup_force_cpu_bug(X86_BUG_ITS); } else if (!strcmp(str, "vmexit")) { its_cmd = ITS_CMD_VMEXIT; + } else if (!strcmp(str, "stuff")) { + its_cmd = ITS_CMD_RSB_STUFF; } else { pr_err("Ignoring unknown indirect_target_selection option (%s).", str); } @@ -1281,6 +1284,12 @@ static void __init its_select_mitigation goto out; }
+ if (cmd == ITS_CMD_RSB_STUFF && + (!boot_cpu_has(X86_FEATURE_RETPOLINE) || !IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING))) { + pr_err("RSB stuff mitigation not supported, using default\n"); + cmd = ITS_CMD_ON; + } + switch (cmd) { case ITS_CMD_OFF: its_mitigation = ITS_MITIGATION_OFF; @@ -1298,6 +1307,16 @@ static void __init its_select_mitigation setup_force_cpu_cap(X86_FEATURE_RETHUNK); set_return_thunk(its_return_thunk); break; + case ITS_CMD_RSB_STUFF: + its_mitigation = ITS_MITIGATION_RETPOLINE_STUFF; + setup_force_cpu_cap(X86_FEATURE_RETHUNK); + setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH); + set_return_thunk(call_depth_return_thunk); + if (retbleed_mitigation == RETBLEED_MITIGATION_NONE) { + retbleed_mitigation = RETBLEED_MITIGATION_STUFF; + pr_info("Retbleed mitigation updated to stuffing\n"); + } + break; } out: pr_info("%s\n", its_strings[its_mitigation]);