[PATCH] x86/bugs: Get rid of the forward declarations

Borislav Petkov
2025-11-14T17:14:41Z

On Wed, Nov 05, 2025 at 09:04:47PM +0100, Borislav Petkov wrote:
> > We should put cpu_select_mitigations() at the bottom too, then all those
> > existing forward declarations can go away.
>
> That's a good idea. We should, if it doesn't get too hairy.

That was easier than I expected. Only build-tested.

---
From: "Borislav Petkov (AMD)" <bp@alien8.de>
Date: Fri, 14 Nov 2025 18:10:04 +0100

Get rid of the forward declarations of the mitigation functions by
moving their single caller below them.

No functional changes.

Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
arch/x86/kernel/cpu/bugs.c | 233 +++++++++++++++----------------------
1 file changed, 93 insertions(+), 140 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d7fa03bf51b4..4fa8284c53a1 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -53,53 +53,6 @@
* mitigation option.
*/

-static void __init spectre_v1_select_mitigation(void);
-static void __init spectre_v1_apply_mitigation(void);
-static void __init spectre_v2_select_mitigation(void);
-static void __init spectre_v2_update_mitigation(void);
-static void __init spectre_v2_apply_mitigation(void);
-static void __init retbleed_select_mitigation(void);
-static void __init retbleed_update_mitigation(void);
-static void __init retbleed_apply_mitigation(void);
-static void __init spectre_v2_user_select_mitigation(void);
-static void __init spectre_v2_user_update_mitigation(void);
-static void __init spectre_v2_user_apply_mitigation(void);
-static void __init ssb_select_mitigation(void);
-static void __init ssb_apply_mitigation(void);
-static void __init l1tf_select_mitigation(void);
-static void __init l1tf_apply_mitigation(void);
-static void __init mds_select_mitigation(void);
-static void __init mds_update_mitigation(void);
-static void __init mds_apply_mitigation(void);
-static void __init taa_select_mitigation(void);
-static void __init taa_update_mitigation(void);
-static void __init taa_apply_mitigation(void);
-static void __init mmio_select_mitigation(void);
-static void __init mmio_update_mitigation(void);
-static void __init mmio_apply_mitigation(void);
-static void __init rfds_select_mitigation(void);
-static void __init rfds_update_mitigation(void);
-static void __init rfds_apply_mitigation(void);
-static void __init srbds_select_mitigation(void);
-static void __init srbds_apply_mitigation(void);
-static void __init l1d_flush_select_mitigation(void);
-static void __init srso_select_mitigation(void);
-static void __init srso_update_mitigation(void);
-static void __init srso_apply_mitigation(void);
-static void __init gds_select_mitigation(void);
-static void __init gds_apply_mitigation(void);
-static void __init bhi_select_mitigation(void);
-static void __init bhi_update_mitigation(void);
-static void __init bhi_apply_mitigation(void);
-static void __init its_select_mitigation(void);
-static void __init its_update_mitigation(void);
-static void __init its_apply_mitigation(void);
-static void __init tsa_select_mitigation(void);
-static void __init tsa_apply_mitigation(void);
-static void __init vmscape_select_mitigation(void);
-static void __init vmscape_update_mitigation(void);
-static void __init vmscape_apply_mitigation(void);
-
/* The base value of the SPEC_CTRL MSR without task-specific bits set */
u64 x86_spec_ctrl_base;
EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);
@@ -233,99 +186,6 @@ static void __init cpu_print_attack_vectors(void)
}
}

-void __init cpu_select_mitigations(void)
-{
- /*
- * Read the SPEC_CTRL MSR to account for reserved bits which may
- * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
- * init code as it is not enumerated and depends on the family.
- */
- if (cpu_feature_enabled(X86_FEATURE_MSR_SPEC_CTRL)) {
- rdmsrq(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
-
- /*
- * Previously running kernel (kexec), may have some controls
- * turned ON. Clear them and let the mitigations setup below
- * rediscover them based on configuration.
- */
- x86_spec_ctrl_base &= ~SPEC_CTRL_MITIGATIONS_MASK;
- }
-
- x86_arch_cap_msr = x86_read_arch_cap_msr();
-
- cpu_print_attack_vectors();
-
- /* Select the proper CPU mitigations before patching alternatives: */
- spectre_v1_select_mitigation();
- spectre_v2_select_mitigation();
- retbleed_select_mitigation();
- spectre_v2_user_select_mitigation();
- ssb_select_mitigation();
- l1tf_select_mitigation();
- mds_select_mitigation();
- taa_select_mitigation();
- mmio_select_mitigation();
- rfds_select_mitigation();
- srbds_select_mitigation();
- l1d_flush_select_mitigation();
- srso_select_mitigation();
- gds_select_mitigation();
- its_select_mitigation();
- bhi_select_mitigation();
- tsa_select_mitigation();
- vmscape_select_mitigation();
-
- /*
- * After mitigations are selected, some may need to update their
- * choices.
- */
- spectre_v2_update_mitigation();
- /*
- * retbleed_update_mitigation() relies on the state set by
- * spectre_v2_update_mitigation(); specifically it wants to know about
- * spectre_v2=ibrs.
- */
- retbleed_update_mitigation();
- /*
- * its_update_mitigation() depends on spectre_v2_update_mitigation()
- * and retbleed_update_mitigation().
- */
- its_update_mitigation();
-
- /*
- * spectre_v2_user_update_mitigation() depends on
- * retbleed_update_mitigation(), specifically the STIBP
- * selection is forced for UNRET or IBPB.
- */
- spectre_v2_user_update_mitigation();
- mds_update_mitigation();
- taa_update_mitigation();
- mmio_update_mitigation();
- rfds_update_mitigation();
- bhi_update_mitigation();
- /* srso_update_mitigation() depends on retbleed_update_mitigation(). */
- srso_update_mitigation();
- vmscape_update_mitigation();
-
- spectre_v1_apply_mitigation();
- spectre_v2_apply_mitigation();
- retbleed_apply_mitigation();
- spectre_v2_user_apply_mitigation();
- ssb_apply_mitigation();
- l1tf_apply_mitigation();
- mds_apply_mitigation();
- taa_apply_mitigation();
- mmio_apply_mitigation();
- rfds_apply_mitigation();
- srbds_apply_mitigation();
- srso_apply_mitigation();
- gds_apply_mitigation();
- its_apply_mitigation();
- bhi_apply_mitigation();
- tsa_apply_mitigation();
- vmscape_apply_mitigation();
-}
-
/*
* NOTE: This function is *only* called for SVM, since Intel uses
* MSR_IA32_SPEC_CTRL for SSBD.
@@ -3371,6 +3231,99 @@ void cpu_bugs_smt_update(void)
mutex_unlock(&spec_ctrl_mutex);
}

+void __init cpu_select_mitigations(void)
+{
+ /*
+ * Read the SPEC_CTRL MSR to account for reserved bits which may
+ * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
+ * init code as it is not enumerated and depends on the family.
+ */
+ if (cpu_feature_enabled(X86_FEATURE_MSR_SPEC_CTRL)) {
+ rdmsrq(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
+
+ /*
+ * Previously running kernel (kexec), may have some controls
+ * turned ON. Clear them and let the mitigations setup below
+ * rediscover them based on configuration.
+ */
+ x86_spec_ctrl_base &= ~SPEC_CTRL_MITIGATIONS_MASK;
+ }
+
+ x86_arch_cap_msr = x86_read_arch_cap_msr();
+
+ cpu_print_attack_vectors();
+
+ /* Select the proper CPU mitigations before patching alternatives: */
+ spectre_v1_select_mitigation();
+ spectre_v2_select_mitigation();
+ retbleed_select_mitigation();
+ spectre_v2_user_select_mitigation();
+ ssb_select_mitigation();
+ l1tf_select_mitigation();
+ mds_select_mitigation();
+ taa_select_mitigation();
+ mmio_select_mitigation();
+ rfds_select_mitigation();
+ srbds_select_mitigation();
+ l1d_flush_select_mitigation();
+ srso_select_mitigation();
+ gds_select_mitigation();
+ its_select_mitigation();
+ bhi_select_mitigation();
+ tsa_select_mitigation();
+ vmscape_select_mitigation();
+
+ /*
+ * After mitigations are selected, some may need to update their
+ * choices.
+ */
+ spectre_v2_update_mitigation();
+ /*
+ * retbleed_update_mitigation() relies on the state set by
+ * spectre_v2_update_mitigation(); specifically it wants to know about
+ * spectre_v2=ibrs.
+ */
+ retbleed_update_mitigation();
+ /*
+ * its_update_mitigation() depends on spectre_v2_update_mitigation()
+ * and retbleed_update_mitigation().
+ */
+ its_update_mitigation();
+
+ /*
+ * spectre_v2_user_update_mitigation() depends on
+ * retbleed_update_mitigation(), specifically the STIBP
+ * selection is forced for UNRET or IBPB.
+ */
+ spectre_v2_user_update_mitigation();
+ mds_update_mitigation();
+ taa_update_mitigation();
+ mmio_update_mitigation();
+ rfds_update_mitigation();
+ bhi_update_mitigation();
+ /* srso_update_mitigation() depends on retbleed_update_mitigation(). */
+ srso_update_mitigation();
+ vmscape_update_mitigation();
+
+ spectre_v1_apply_mitigation();
+ spectre_v2_apply_mitigation();
+ retbleed_apply_mitigation();
+ spectre_v2_user_apply_mitigation();
+ ssb_apply_mitigation();
+ l1tf_apply_mitigation();
+ mds_apply_mitigation();
+ taa_apply_mitigation();
+ mmio_apply_mitigation();
+ rfds_apply_mitigation();
+ srbds_apply_mitigation();
+ srso_apply_mitigation();
+ gds_apply_mitigation();
+ its_apply_mitigation();
+ bhi_apply_mitigation();
+ tsa_apply_mitigation();
+ vmscape_apply_mitigation();
+}
+
#ifdef CONFIG_SYSFS

#define L1TF_DEFAULT_MSG "Mitigation: PTE Inversion"
--
2.51.0

--
Regards/Gruss,
Boris.