The following commit has been merged into the x86/alternatives branch of tip:
Commit-ID: 4175b45dec4cd8ae4563bf724d591ab5cc0ad9ce
Gitweb: https://git.kernel.org/tip/4175b45dec4cd8ae4563bf724d591ab5cc0ad9ce
Author: Borislav Petkov (AMD) <bp@xxxxxxxxx>
AuthorDate: Wed, 27 Mar 2024 16:43:14 +01:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Thu, 04 Apr 2024 12:09:17 +02:00
x86/alternatives: Catch late X86_FEATURE modifiers
After alternatives have been patched, changes to the X86_FEATURE flags
won't take effect and could potentially even be wrong.
Warn about it.
This is something which has been long overdue.
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Tested-by: Srikanth Aithal <sraithal@xxxxxxx>
Link: https://lore.kernel.org/r/20240327154317.29909-3-bp@xxxxxxxxx
---
arch/x86/include/asm/cpufeature.h | 8 ++++++--
arch/x86/kernel/cpu/cpuid-deps.c | 3 +++
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 17fd7be..f8d7a06 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -148,8 +148,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
extern void setup_clear_cpu_cap(unsigned int bit);
extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
-#define setup_force_cpu_cap(bit) do { \
- set_cpu_cap(&boot_cpu_data, bit); \
+#define setup_force_cpu_cap(bit) do { \
+ \
+ if (!boot_cpu_has(bit)) \
+ WARN_ON(alternatives_patched); \
+ \
+ set_cpu_cap(&boot_cpu_data, bit); \
set_bit(bit, (unsigned long *)cpu_caps_set); \
} while (0)
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index b717420..5dd427c 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -114,6 +114,9 @@ static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
if (WARN_ON(feature >= MAX_FEATURE_BITS))
return;
+ if (boot_cpu_has(feature))
+ WARN_ON(alternatives_patched);
+
clear_feature(c, feature);
/* Collect all features to disable, handling dependencies */
|