[PATCH v3 1/8] x86/split_lock: Export handle_user_split_lock()

Xiaoyao Li
2020-02-06T07:09:25Z

Move the EFLAGS.AC check to do_alignment_check() so that
handle_user_split_lock() can be used by KVM in the future to handle #AC
caused by split lock in guest.

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
arch/x86/include/asm/cpu.h | 4 ++--
arch/x86/kernel/cpu/intel.c | 7 ++++---
arch/x86/kernel/traps.c | 2 +-
3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index ff6f3ca649b3..ff567afa6ee1 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -43,11 +43,11 @@ unsigned int x86_stepping(unsigned int sig);
#ifdef CONFIG_CPU_SUP_INTEL
extern void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c);
extern void switch_to_sld(unsigned long tifn);
-extern bool handle_user_split_lock(struct pt_regs *regs, long error_code);
+extern bool handle_user_split_lock(unsigned long ip);
#else
static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {}
static inline void switch_to_sld(unsigned long tifn) {}
-static inline bool handle_user_split_lock(struct pt_regs *regs, long error_code)
+static inline bool handle_user_split_lock(unsigned long ip)
{
return false;
}
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index db3e745e5d47..2b3874a96bd4 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -1058,13 +1058,13 @@ static void split_lock_init(void)
sld_state = sld_off;
}

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

pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n",
- current->comm, current->pid, regs->ip);
+ current->comm, current->pid, ip);

/*
* Disable the split lock detection for this task so it can make
@@ -1075,6 +1075,7 @@ bool handle_user_split_lock(struct pt_regs *regs, long error_code)
set_tsk_thread_flag(current, TIF_SLD);
return true;
}
+EXPORT_SYMBOL_GPL(handle_user_split_lock);

/*
* This function is called only when switching between tasks with
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 0ef5befaed7d..407ff9be610f 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -304,7 +304,7 @@ dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code)

local_irq_enable();

- if (handle_user_split_lock(regs, error_code))
+ if (!(regs->flags & X86_EFLAGS_AC) && handle_user_split_lock(regs->ip))
return;

do_trap(X86_TRAP_AC, SIGBUS, "alignment check", regs,
--
2.23.0