From: David Kaplan Date: Fri, 18 Apr 2025 16:17:19 +0000 (-0500) Subject: x86/bugs: Restructure SSB mitigation X-Git-Tag: v6.16-rc1~195^2~31^2~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5ece59a2fca6e1467558467a05cf742b7e52d1b7;p=thirdparty%2Fkernel%2Flinux.git x86/bugs: Restructure SSB mitigation Restructure SSB to use select/apply functions to create consistent vulnerability handling. Remove __ssb_select_mitigation() and split the functionality between the select/apply functions. Signed-off-by: David Kaplan Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Josh Poimboeuf Link: https://lore.kernel.org/20250418161721.1855190-15-david.kaplan@amd.com --- diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 93d07438eea78..fbb4f1378de1f 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -65,6 +65,7 @@ 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 mds_select_mitigation(void); static void __init mds_update_mitigation(void); @@ -243,6 +244,7 @@ void __init cpu_select_mitigations(void) spectre_v2_apply_mitigation(); retbleed_apply_mitigation(); spectre_v2_user_apply_mitigation(); + ssb_apply_mitigation(); mds_apply_mitigation(); taa_apply_mitigation(); mmio_apply_mitigation(); @@ -2219,19 +2221,18 @@ static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void) return cmd; } -static enum ssb_mitigation __init __ssb_select_mitigation(void) +static void __init ssb_select_mitigation(void) { - enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE; enum ssb_mitigation_cmd cmd; if (!boot_cpu_has(X86_FEATURE_SSBD)) - return mode; + goto out; cmd = ssb_parse_cmdline(); if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) && (cmd == SPEC_STORE_BYPASS_CMD_NONE || cmd == SPEC_STORE_BYPASS_CMD_AUTO)) - return mode; + return; switch (cmd) { case SPEC_STORE_BYPASS_CMD_SECCOMP: @@ -2240,28 +2241,35 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void) * enabled. */ if (IS_ENABLED(CONFIG_SECCOMP)) - mode = SPEC_STORE_BYPASS_SECCOMP; + ssb_mode = SPEC_STORE_BYPASS_SECCOMP; else - mode = SPEC_STORE_BYPASS_PRCTL; + ssb_mode = SPEC_STORE_BYPASS_PRCTL; break; case SPEC_STORE_BYPASS_CMD_ON: - mode = SPEC_STORE_BYPASS_DISABLE; + ssb_mode = SPEC_STORE_BYPASS_DISABLE; break; case SPEC_STORE_BYPASS_CMD_AUTO: case SPEC_STORE_BYPASS_CMD_PRCTL: - mode = SPEC_STORE_BYPASS_PRCTL; + ssb_mode = SPEC_STORE_BYPASS_PRCTL; break; case SPEC_STORE_BYPASS_CMD_NONE: break; } +out: + if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) + pr_info("%s\n", ssb_strings[ssb_mode]); +} + +static void __init ssb_apply_mitigation(void) +{ /* * We have three CPU feature flags that are in play here: * - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible. * - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass * - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation */ - if (mode == SPEC_STORE_BYPASS_DISABLE) { + if (ssb_mode == SPEC_STORE_BYPASS_DISABLE) { setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE); /* * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may @@ -2275,16 +2283,6 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void) update_spec_ctrl(x86_spec_ctrl_base); } } - - return mode; -} - -static void ssb_select_mitigation(void) -{ - ssb_mode = __ssb_select_mitigation(); - - if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) - pr_info("%s\n", ssb_strings[ssb_mode]); } #undef pr_fmt