| Message ID | 2e062b6c142bb3770a0829e2cf21e11e8fb6ae5c.1732087270.git.jpoimboe@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | x86/bugs: RSB tweaks | expand |
On Tue, Nov 19, 2024 at 11:27:50PM -0800, Josh Poimboeuf wrote: > eIBRS protects against RSB underflow/poisoning attacks. Adding > retpoline to the mix doesn't change that. Retpoline has a balanced > CALL/RET anyway. > > So the current full RSB filling on VMEXIT with eIBRS+retpoline is > overkill. Disable it (or do the VMEXIT_LITE mitigation if needed). > > Suggested-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Reviewed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 47a01d4028f6..68bed17f0980 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1605,20 +1605,20 @@ static void __init spectre_v2_determine_rsb_fill_type_at_vmexit(enum spectre_v2_ case SPECTRE_V2_NONE: return; - case SPECTRE_V2_EIBRS_LFENCE: case SPECTRE_V2_EIBRS: + case SPECTRE_V2_EIBRS_LFENCE: + case SPECTRE_V2_EIBRS_RETPOLINE: if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) { - setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE); pr_info("Spectre v2 / PBRSB-eIBRS: Retire a single CALL on VMEXIT\n"); + setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE); } return; - case SPECTRE_V2_EIBRS_RETPOLINE: case SPECTRE_V2_RETPOLINE: case SPECTRE_V2_LFENCE: case SPECTRE_V2_IBRS: - setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT); pr_info("Spectre v2 / SpectreRSB : Filling RSB on VMEXIT\n"); + setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT); return; }
eIBRS protects against RSB underflow/poisoning attacks. Adding retpoline to the mix doesn't change that. Retpoline has a balanced CALL/RET anyway. So the current full RSB filling on VMEXIT with eIBRS+retpoline is overkill. Disable it (or do the VMEXIT_LITE mitigation if needed). Suggested-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> --- arch/x86/kernel/cpu/bugs.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)