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Subject[PATCH v6 12/13] x86/bugs: spectre_v2_user default mode depends on Kconfig
Date
Change the default value of spectre v2 in user mode to respect the
CONFIG_MITIGATION_SPECTRE_V2 config option.

Currently, user mode spectre v2 is set to auto
(SPECTRE_V2_USER_CMD_AUTO) by default, even if
CONFIG_MITIGATION_SPECTRE_V2 is disabled.

Set the Spectre_v2 value to auto (SPECTRE_V2_USER_CMD_AUTO) if the
Spectre v2 config (CONFIG_MITIGATION_SPECTRE_V2) is enabled, otherwise
set the value to none (SPECTRE_V2_USER_CMD_NONE).

Important to say the command line argument "spectre_v2_user" overwrites
the default value in both cases.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
arch/x86/kernel/cpu/bugs.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 0172bb0f61fe..a99f8c064682 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1216,8 +1216,11 @@ static __ro_after_init enum spectre_v2_mitigation_cmd spectre_v2_cmd;
static enum spectre_v2_user_cmd __init
spectre_v2_parse_user_cmdline(void)
{
+ int ret, i, mode;
char arg[20];
- int ret, i;
+
+ mode = IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ?
+ SPECTRE_V2_USER_CMD_AUTO : SPECTRE_V2_USER_CMD_NONE;

switch (spectre_v2_cmd) {
case SPECTRE_V2_CMD_NONE:
@@ -1231,7 +1234,7 @@ spectre_v2_parse_user_cmdline(void)
ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
arg, sizeof(arg));
if (ret < 0)
- return SPECTRE_V2_USER_CMD_AUTO;
+ return mode;

for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
if (match_option(arg, ret, v2_user_options[i].option)) {
@@ -1241,8 +1244,8 @@ spectre_v2_parse_user_cmdline(void)
}
}

- pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg);
- return SPECTRE_V2_USER_CMD_AUTO;
+ pr_err("Unknown user space protection option (%s). Switching to default\n", arg);
+ return mode;
}

static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)
--
2.34.1
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