diff options
| author | Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2024-11-18 09:53:12 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-05-18 08:21:26 +0200 |
| commit | 139c0b8318c2ea8afd2f12b6401466c6010286da (patch) | |
| tree | 9e035ba3e8a79e3e1be625b8dbd02bcfa326912d /arch/x86/kernel/cpu/bugs.c | |
| parent | b1701fee52d1d68d1e12ad140b3551435a8e9fe7 (diff) | |
x86/its: Add "vmexit" option to skip mitigation on some CPUs
commit 2665281a07e19550944e8354a2024635a7b2714a upstream.
Ice Lake generation CPUs are not affected by guest/host isolation part of
ITS. If a user is only concerned about KVM guests, they can now choose a
new cmdline option "vmexit" that will not deploy the ITS mitigation when
CPU is not affected by guest/host isolation. This saves the performance
overhead of ITS mitigation on Ice Lake gen CPUs.
When "vmexit" option selected, if the CPU is affected by ITS guest/host
isolation, the default ITS mitigation 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>
Diffstat (limited to 'arch/x86/kernel/cpu/bugs.c')
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 30fbe241da42..766cee7fa905 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1158,15 +1158,18 @@ do_cmd_auto: enum its_mitigation_cmd { ITS_CMD_OFF, ITS_CMD_ON, + ITS_CMD_VMEXIT, }; enum its_mitigation { ITS_MITIGATION_OFF, + ITS_MITIGATION_VMEXIT_ONLY, ITS_MITIGATION_ALIGNED_THUNKS, }; static const char * const its_strings[] = { [ITS_MITIGATION_OFF] = "Vulnerable", + [ITS_MITIGATION_VMEXIT_ONLY] = "Mitigation: Vulnerable, KVM: Not affected", [ITS_MITIGATION_ALIGNED_THUNKS] = "Mitigation: Aligned branch/return thunks", }; @@ -1192,6 +1195,8 @@ static int __init its_parse_cmdline(char *str) } else if (!strcmp(str, "force")) { its_cmd = ITS_CMD_ON; setup_force_cpu_bug(X86_BUG_ITS); + } else if (!strcmp(str, "vmexit")) { + its_cmd = ITS_CMD_VMEXIT; } else { pr_err("Ignoring unknown indirect_target_selection option (%s).", str); } @@ -1239,6 +1244,12 @@ static void __init its_select_mitigation(void) case ITS_CMD_OFF: its_mitigation = ITS_MITIGATION_OFF; break; + case ITS_CMD_VMEXIT: + if (boot_cpu_has_bug(X86_BUG_ITS_NATIVE_ONLY)) { + its_mitigation = ITS_MITIGATION_VMEXIT_ONLY; + goto out; + } + fallthrough; case ITS_CMD_ON: its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS; if (!boot_cpu_has(X86_FEATURE_RETPOLINE)) |