[PATCH 5.10 103/148] x86/bugs: Split spectre_v2_select_mitigation() and spectre_v2_user_select_mitigation()

Greg Kroah-Hartman
2022-07-23T10:08:05Z

From: Peter Zijlstra <peterz@infradead.org>

commit 166115c08a9b0b846b783088808a27d739be6e8d upstream.

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>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/cpu/bugs.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

--- 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);
@@ -137,13 +138,19 @@ 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();
@@ -969,13 +976,15 @@ static void __init spec_v2_user_print_co
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:
@@ -1010,7 +1019,7 @@ static inline bool spectre_v2_in_ibrs_mo
}

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);
@@ -1023,7 +1032,7 @@ spectre_v2_user_select_mitigation(enum s
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;
@@ -1347,7 +1356,7 @@ static void __init spectre_v2_select_mit
}

/* 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)