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x86/its: Add support for RSB stuffing mitigation

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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>
This commit is contained in:
Pawan Gupta
2024-12-02 12:07:08 -08:00
committed by Dave Hansen
parent 2665281a07
commit facd226f7e
2 changed files with 22 additions and 0 deletions
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3
Documentation/admin-guide/kernel-parameters.txt
View File

@@ -2212,6 +2212,9 @@
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

19
arch/x86/kernel/cpu/bugs.c
View File

@@ -1204,6 +1204,7 @@ enum its_mitigation_cmd {
ITS_CMD_OFF,
ITS_CMD_ON,
ITS_CMD_VMEXIT,
ITS_CMD_RSB_STUFF,
};
enum its_mitigation {
@@ -1244,6 +1245,8 @@ static int __init its_parse_cmdline(char *str)
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);
}
@@ -1295,6 +1298,12 @@ static void __init its_select_mitigation(void)
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;
@@ -1312,6 +1321,16 @@ static void __init its_select_mitigation(void)
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]);