[patch V4 part 1 14/36] x86/entry: Get rid of ist_begin/end_non_atomic()

Thomas Gleixner
2020-05-05T14:23:18Z

This is completely overengineered and definitely not an interface which
should be made available to anything else than this particular MCE case.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/traps.h | 2 --
arch/x86/kernel/cpu/mce/core.c | 6 ++++--
arch/x86/kernel/traps.c | 37 -------------------------------------
3 files changed, 4 insertions(+), 41 deletions(-)

--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -120,8 +120,6 @@ asmlinkage void smp_irq_move_cleanup_int

extern void ist_enter(struct pt_regs *regs);
extern void ist_exit(struct pt_regs *regs);
-extern void ist_begin_non_atomic(struct pt_regs *regs);
-extern void ist_end_non_atomic(void);

#ifdef CONFIG_VMAP_STACK
void __noreturn handle_stack_overflow(const char *message,
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1352,13 +1352,15 @@ void notrace do_machine_check(struct pt_

/* Fault was in user mode and we need to take some action */
if ((m.cs & 3) == 3) {
- ist_begin_non_atomic(regs);
+ /* If this triggers there is no way to recover. Die hard. */
+ BUG_ON(!on_thread_stack() || !user_mode(regs));
local_irq_enable();
+ preempt_enable();

if (kill_it || do_memory_failure(&m))
force_sig(SIGBUS);
+ preempt_disable();
local_irq_disable();
- ist_end_non_atomic();
} else {
if (!fixup_exception(regs, X86_TRAP_MC, error_code, 0))
mce_panic("Failed kernel mode recovery", &m, msg);
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -117,43 +117,6 @@ void ist_exit(struct pt_regs *regs)
rcu_nmi_exit();
}

-/**
- * ist_begin_non_atomic() - begin a non-atomic section in an IST exception
- * @regs: regs passed to the IST exception handler
- *
- * IST exception handlers normally cannot schedule. As a special
- * exception, if the exception interrupted userspace code (i.e.
- * user_mode(regs) would return true) and the exception was not
- * a double fault, it can be safe to schedule. ist_begin_non_atomic()
- * begins a non-atomic section within an ist_enter()/ist_exit() region.
- * Callers are responsible for enabling interrupts themselves inside
- * the non-atomic section, and callers must call ist_end_non_atomic()
- * before ist_exit().
- */
-void ist_begin_non_atomic(struct pt_regs *regs)
-{
- BUG_ON(!user_mode(regs));
-
- /*
- * Sanity check: we need to be on the normal thread stack. This
- * will catch asm bugs and any attempt to use ist_preempt_enable
- * from double_fault.
- */
- BUG_ON(!on_thread_stack());
-
- preempt_enable_no_resched();
-}
-
-/**
- * ist_end_non_atomic() - begin a non-atomic section in an IST exception
- *
- * Ends a non-atomic section started with ist_begin_non_atomic().
- */
-void ist_end_non_atomic(void)
-{
- preempt_disable();
-}
-
int is_valid_bugaddr(unsigned long addr)
{
unsigned short ud;