From: Peter Zijlstra <peterz@infradead.org>

Date: Tue, 14 Jun 2022 23:15:56 +0200

Subject: x86/bugs: Split spectre_v2_select_mitigation() and

 spectre_v2_user_select_mitigation()

Git-commit: 166115c08a9b0b846b783088808a27d739be6e8d

Patch-mainline: v5.19-rc4

References: bsc#1199657 CVE-2022-29900 CVE-2022-29901

retbleed will depend on spectre_v2, while spectre_v2_user depends on

retbleed. Break this cycle.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Signed-off-by: Borislav Petkov <bp@suse.de>

Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>

Signed-off-by: Borislav Petkov <bp@suse.de>

---

 arch/x86/kernel/cpu/bugs.c | 25 +++++++++++++++++--------

 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c

index 2d7896493220..c546a9e4ed17 100644

--- a/arch/x86/kernel/cpu/bugs.c

+++ b/arch/x86/kernel/cpu/bugs.c

@@ -37,8 +37,9 @@

 #include "cpu.h"

 static void __init spectre_v1_select_mitigation(void);

-static void __init retbleed_select_mitigation(void);

 static void __init spectre_v2_select_mitigation(void);

+static void __init retbleed_select_mitigation(void);

+static void __init spectre_v2_user_select_mitigation(void);

 static void __init ssb_select_mitigation(void);

 static void __init l1tf_select_mitigation(void);

 static void __init mds_select_mitigation(void);

@@ -145,13 +146,19 @@ void __init check_bugs(void)

 	/* Select the proper CPU mitigations before patching alternatives: */

 	spectre_v1_select_mitigation();

+	spectre_v2_select_mitigation();

+	/*

+	 * retbleed_select_mitigation() relies on the state set by

+	 * spectre_v2_select_mitigation(); specifically it wants to know about

+	 * spectre_v2=ibrs.

+	 */

 	retbleed_select_mitigation();

 	/*

-	 * spectre_v2_select_mitigation() relies on the state set by

+	 * spectre_v2_user_select_mitigation() relies on the state set by

 	 * retbleed_select_mitigation(); specifically the STIBP selection is

 	 * forced for UNRET.

 	 */

-	spectre_v2_select_mitigation();

+	spectre_v2_user_select_mitigation();

 	ssb_select_mitigation();

 	l1tf_select_mitigation();

 	md_clear_select_mitigation();

@@ -1013,13 +1020,15 @@ static void __init spec_v2_user_print_cond(const char *reason, bool secure)

 		pr_info("spectre_v2_user=%s forced on command line.\n", reason);

 }

+static __ro_after_init enum spectre_v2_mitigation_cmd spectre_v2_cmd;

+

 static enum spectre_v2_user_cmd __init

-spectre_v2_parse_user_cmdline(enum spectre_v2_mitigation_cmd v2_cmd)

+spectre_v2_parse_user_cmdline(void)

 {

 	char arg[20];

 	int ret, i;

-	switch (v2_cmd) {

+	switch (spectre_v2_cmd) {

 	case SPECTRE_V2_CMD_NONE:

 		return SPECTRE_V2_USER_CMD_NONE;

 	case SPECTRE_V2_CMD_FORCE:

@@ -1054,7 +1063,7 @@ static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)

 }

 static void __init

-spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)

+spectre_v2_user_select_mitigation(void)

 {

 	enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE;

 	bool smt_possible = IS_ENABLED(CONFIG_SMP);

@@ -1067,7 +1076,7 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)

 	    cpu_smt_control == CPU_SMT_NOT_SUPPORTED)

 		smt_possible = false;

-	cmd = spectre_v2_parse_user_cmdline(v2_cmd);

+	cmd = spectre_v2_parse_user_cmdline();

 	switch (cmd) {

 	case SPECTRE_V2_USER_CMD_NONE:

 		goto set_mode;

@@ -1391,7 +1400,7 @@ static void __init spectre_v2_select_mitigation(void)

 	}

 	/* Set up IBPB and STIBP depending on the general spectre V2 command */

-	spectre_v2_user_select_mitigation(cmd);

+	spectre_v2_cmd = cmd;

 }

 static void update_stibp_msr(void * __unused)