The following commit has been merged into the x86/bugs branch of tip:
Commit-ID: 98fdaeb296f51ef08e727a7cc72e5b5c864c4f4d
Gitweb: https://git.kernel.org/tip/98fdaeb296f51ef08e727a7cc72e5b5c864c4f4d
Author: Breno Leitao <leitao@xxxxxxxxxx>
AuthorDate: Thu, 31 Oct 2024 04:06:17 -07:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Mon, 03 Mar 2025 12:48:41 +01:00
x86/bugs: Make spectre user default depend on MITIGATION_SPECTRE_V2
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.
When CONFIG_MITIGATION_SPECTRE_V2 is not set, users have the flexibility
to opt-in for specific mitigations independently. In this scenario,
setting spectre_v2= will not enable spectre_v2_user=, and command line
options spectre_v2_user and spectre_v2 are independent when
CONFIG_MITIGATION_SPECTRE_V2=n.
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: David Kaplan <David.Kaplan@xxxxxxx>
Link: https://lore.kernel.org/r/20241031-x86_bugs_last_v2-v2-2-b7ff1dab840e@xxxxxxxxxx
---
Documentation/admin-guide/kernel-parameters.txt | 2 ++
arch/x86/kernel/cpu/bugs.c | 10 +++++++---
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index fb8752b..274b71a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6582,6 +6582,8 @@
Selecting 'on' will also enable the mitigation
against user space to user space task attacks.
+ Selecting specific mitigation does not force enable
+ user mitigations.
Selecting 'off' will disable both the kernel and
the user space protections.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 346bebf..4386aa6 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1308,9 +1308,13 @@ 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)
{
+ enum spectre_v2_user_cmd 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:
return SPECTRE_V2_USER_CMD_NONE;
@@ -1323,7 +1327,7 @@ 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)) {
@@ -1333,8 +1337,8 @@ 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)
|