diff options
| author |   Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2025-05-05 14:35:12 -0700 |
|---|---|---|
| committer |   Dave Hansen <dave.hansen@linux.intel.com> | 2025-05-06 08:18:59 -0700 |
| commit | 073fdbe02c69c43fb7c0d547ec265c7747d4a646 (patch) | |
| tree | 453bb3e1a7c95014cea041fd2f1779594171db80 | |
| parent | x86/bpf: Add IBHF call at end of classic BPF (diff) | |
| download | wireguard-linux-073fdbe02c69c43fb7c0d547ec265c7747d4a646.tar.xz wireguard-linux-073fdbe02c69c43fb7c0d547ec265c7747d4a646.zip | |
x86/bhi: Do not set BHI_DIS_S in 32-bit mode
With the possibility of intra-mode BHI via cBPF, complete mitigation for
BHI is to use IBHF (history fence) instruction with BHI_DIS_S set. Since
this new instruction is only available in 64-bit mode, setting BHI_DIS_S in
32-bit mode is only a partial mitigation.
Do not set BHI_DIS_S in 32-bit mode so as to avoid reporting misleading
mitigated status. With this change IBHF won't be used in 32-bit mode, also
remove the CONFIG_X86_64 check from emit_spectre_bhb_barrier().
Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org>
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>
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 6 | ||||
| -rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 5 |
2 files changed, 6 insertions, 5 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 362602b705cc..f219f0f4f2d1 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1697,11 +1697,11 @@ static void __init bhi_select_mitigation(void) return; } - /* Mitigate in hardware if supported */ - if (spec_ctrl_bhi_dis()) + if (!IS_ENABLED(CONFIG_X86_64)) return; - if (!IS_ENABLED(CONFIG_X86_64)) + /* Mitigate in hardware if supported */ + if (spec_ctrl_bhi_dis()) return; if (bhi_mitigation == BHI_MITIGATION_VMEXIT_ONLY) { diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index e472572392ef..8a0fabb850b7 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1527,8 +1527,7 @@ static int emit_spectre_bhb_barrier(u8 **pprog, u8 *ip, /* Insert IBHF instruction */ if ((cpu_feature_enabled(X86_FEATURE_CLEAR_BHB_LOOP) && cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) || - (cpu_feature_enabled(X86_FEATURE_CLEAR_BHB_HW) && - IS_ENABLED(CONFIG_X86_64))) { + cpu_feature_enabled(X86_FEATURE_CLEAR_BHB_HW)) { /* * Add an Indirect Branch History Fence (IBHF). IBHF acts as a * fence preventing branch history from before the fence from @@ -1538,6 +1537,8 @@ static int emit_spectre_bhb_barrier(u8 **pprog, u8 *ip, * hardware that doesn't need or support it. The REP and REX.W * prefixes are required by the microcode, and they also ensure * that the NOP is unlikely to be used in existing code. + * + * IBHF is not a valid instruction in 32-bit mode. */ EMIT5(0xF3, 0x48, 0x0F, 0x1E, 0xF8); /* ibhf */ } |