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Subject[PATCH v9 3/8] x86/split_lock: Introduce flag X86_FEATURE_SLD_FATAL and drop sld_state
Date
Introduce a synthetic feature flag X86_FEATURE_SLD_FATAL, which means
kernel is in sld_fatal mode if set.

Now sld_state is not needed any more that the state of SLD can be
inferred from X86_FEATURE_SPLIT_LOCK_DETECT and X86_FEATURE_SLD_FATAL.

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kernel/cpu/intel.c | 16 ++++++----------
2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index db189945e9b0..260adfc6c61a 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -286,6 +286,7 @@
#define X86_FEATURE_FENCE_SWAPGS_USER (11*32+ 4) /* "" LFENCE in user entry SWAPGS path */
#define X86_FEATURE_FENCE_SWAPGS_KERNEL (11*32+ 5) /* "" LFENCE in kernel entry SWAPGS path */
#define X86_FEATURE_SPLIT_LOCK_DETECT (11*32+ 6) /* #AC for split lock */
+#define X86_FEATURE_SLD_FATAL (11*32+ 7) /* split lock detection in fatal mode */

/* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
#define X86_FEATURE_AVX512_BF16 (12*32+ 5) /* AVX512 BFLOAT16 instructions */
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 4602dac14dcb..93b8ccf2fa11 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -40,12 +40,6 @@ enum split_lock_detect_state {
sld_fatal,
};

-/*
- * Default to sld_off because most systems do not support split lock detection
- * split_lock_setup() will switch this to sld_warn on systems that support
- * split lock detect, unless there is a command line override.
- */
-static enum split_lock_detect_state sld_state __ro_after_init = sld_off;
static u64 msr_test_ctrl_cache __ro_after_init;

/*
@@ -1043,8 +1037,9 @@ static void __init split_lock_setup(void)
return;
}

- sld_state = state;
setup_force_cpu_cap(X86_FEATURE_SPLIT_LOCK_DETECT);
+ if (state == sld_fatal)
+ setup_force_cpu_cap(X86_FEATURE_SLD_FATAL);
}

/*
@@ -1064,7 +1059,7 @@ static void sld_update_msr(bool on)

static void split_lock_init(void)
{
- split_lock_verify_msr(sld_state != sld_off);
+ split_lock_verify_msr(boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT));
}

static void split_lock_warn(unsigned long ip)
@@ -1083,7 +1078,7 @@ static void split_lock_warn(unsigned long ip)

bool handle_guest_split_lock(unsigned long ip)
{
- if (sld_state == sld_warn) {
+ if (!boot_cpu_has(X86_FEATURE_SLD_FATAL)) {
split_lock_warn(ip);
return true;
}
@@ -1100,7 +1095,8 @@ EXPORT_SYMBOL_GPL(handle_guest_split_lock);

bool handle_user_split_lock(struct pt_regs *regs, long error_code)
{
- if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal)
+ if ((regs->flags & X86_EFLAGS_AC) ||
+ boot_cpu_has(X86_FEATURE_SLD_FATAL))
return false;
split_lock_warn(regs->ip);
return true;
--
2.18.2
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