The following commit has been merged into the x86/bugs branch of tip:
Commit-ID: efe313827c98c81156dea9b004877db4ca728b1a
Gitweb: https://git.kernel.org/tip/efe313827c98c81156dea9b004877db4ca728b1a
Author: David Kaplan <david.kaplan@amd.com>
AuthorDate: Fri, 18 Apr 2025 11:17:17 -05:00
Committer: Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 29 Apr 2025 18:51:29 +02:00
x86/bugs: Restructure BHI mitigation
Restructure BHI mitigation to use select/update/apply functions to create
consistent vulnerability handling. BHI mitigation was previously selected
from within spectre_v2_select_mitigation() and now is selected from
cpu_select_mitigation() like with all others.
Define new AUTO mitigation for BHI.
Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/20250418161721.1855190-13-david.kaplan@amd.com
---
arch/x86/kernel/cpu/bugs.c | 31 +++++++++++++++++++++++++++----
1 file changed, 27 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index dc75195..100a320 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -82,6 +82,9 @@ static void __init l1d_flush_select_mitigation(void);
static void __init srso_select_mitigation(void);
static void __init gds_select_mitigation(void);
static void __init gds_apply_mitigation(void);
+static void __init bhi_select_mitigation(void);
+static void __init bhi_update_mitigation(void);
+static void __init bhi_apply_mitigation(void);
/* The base value of the SPEC_CTRL MSR without task-specific bits set */
u64 x86_spec_ctrl_base;
@@ -208,6 +211,7 @@ void __init cpu_select_mitigations(void)
*/
srso_select_mitigation();
gds_select_mitigation();
+ bhi_select_mitigation();
/*
* After mitigations are selected, some may need to update their
@@ -225,6 +229,7 @@ void __init cpu_select_mitigations(void)
taa_update_mitigation();
mmio_update_mitigation();
rfds_update_mitigation();
+ bhi_update_mitigation();
spectre_v1_apply_mitigation();
retbleed_apply_mitigation();
@@ -235,6 +240,7 @@ void __init cpu_select_mitigations(void)
rfds_apply_mitigation();
srbds_apply_mitigation();
gds_apply_mitigation();
+ bhi_apply_mitigation();
}
/*
@@ -1794,12 +1800,13 @@ static bool __init spec_ctrl_bhi_dis(void)
enum bhi_mitigations {
BHI_MITIGATION_OFF,
+ BHI_MITIGATION_AUTO,
BHI_MITIGATION_ON,
BHI_MITIGATION_VMEXIT_ONLY,
};
static enum bhi_mitigations bhi_mitigation __ro_after_init =
- IS_ENABLED(CONFIG_MITIGATION_SPECTRE_BHI) ? BHI_MITIGATION_ON : BHI_MITIGATION_OFF;
+ IS_ENABLED(CONFIG_MITIGATION_SPECTRE_BHI) ? BHI_MITIGATION_AUTO : BHI_MITIGATION_OFF;
static int __init spectre_bhi_parse_cmdline(char *str)
{
@@ -1821,6 +1828,25 @@ early_param("spectre_bhi", spectre_bhi_parse_cmdline);
static void __init bhi_select_mitigation(void)
{
+ if (!boot_cpu_has(X86_BUG_BHI) || cpu_mitigations_off())
+ bhi_mitigation = BHI_MITIGATION_OFF;
+
+ if (bhi_mitigation == BHI_MITIGATION_AUTO)
+ bhi_mitigation = BHI_MITIGATION_ON;
+}
+
+static void __init bhi_update_mitigation(void)
+{
+ if (spectre_v2_cmd == SPECTRE_V2_CMD_NONE)
+ bhi_mitigation = BHI_MITIGATION_OFF;
+
+ if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
+ spectre_v2_cmd == SPECTRE_V2_CMD_AUTO)
+ bhi_mitigation = BHI_MITIGATION_OFF;
+}
+
+static void __init bhi_apply_mitigation(void)
+{
if (bhi_mitigation == BHI_MITIGATION_OFF)
return;
@@ -1961,9 +1987,6 @@ static void __init spectre_v2_select_mitigation(void)
mode == SPECTRE_V2_RETPOLINE)
spec_ctrl_disable_kernel_rrsba();
- if (boot_cpu_has(X86_BUG_BHI))
- bhi_select_mitigation();
-
spectre_v2_enabled = mode;
pr_info("%s\n", spectre_v2_strings[mode]);