From: Josh Poimboeuf jpoimboe@kernel.org
[ Upstream commit 18bae0dfec15b24ec14ca17dc18603372f5f254f ]
eIBRS protects against guest->host 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 Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com Reviewed-by: Amit Shah amit.shah@amd.com Reviewed-by: Nikolay Borisov nik.borisov@suse.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Vitaly Kuznetsov vkuznets@redhat.com Cc: Sean Christopherson seanjc@google.com Cc: David Woodhouse dwmw2@infradead.org Link: https://lore.kernel.org/r/84a1226e5c9e2698eae1b5ade861f1b8bf3677dc.174414825... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/cpu/bugs.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 725f827718a71..045ab6d0a98bb 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1543,20 +1543,20 @@ 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; }