linux-kernel - [PATCH v3 1/8] x86/split_lock: Export handle_user_split

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Date:   Thu,  6 Feb 2020 15:04:05 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        hpa@...or.com, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...nel.org>, tony.luck@...el.com
Cc:     peterz@...radead.org, fenghua.yu@...el.com, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: [PATCH v3 1/8] x86/split_lock: Export handle_user_split_lock()

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@...el.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.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