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Subject[tip: x86/entry] x86/mce: Move nmi_enter/exit() into the entry point
The following commit has been merged into the x86/entry branch of tip:

Commit-ID: 46dbb1443cd5c4e1c892b820d7a578995a1708cf
Gitweb: https://git.kernel.org/tip/46dbb1443cd5c4e1c892b820d7a578995a1708cf
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Fri, 03 Apr 2020 22:37:31 +02:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 19 May 2020 16:04:08 +02:00

x86/mce: Move nmi_enter/exit() into the entry point

There is no reason to have nmi_enter/exit() in the actual MCE
handlers. Move it to the entry point. This also covers the until now
uncovered initial handler which only prints.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135314.243936614@linutronix.de


---
arch/x86/kernel/cpu/mce/core.c | 26 +++++++++++++-------------
arch/x86/kernel/cpu/mce/p5.c | 4 ----
arch/x86/kernel/cpu/mce/winchip.c | 4 ----
3 files changed, 13 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index e9265e2..f5993ed 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1100,8 +1100,10 @@ static void mce_clear_state(unsigned long *toclear)
* kdump kernel establishing a new #MC handler where a broadcasted MCE
* might not get handled properly.
*/
-static bool __mc_check_crashing_cpu(int cpu)
+static noinstr bool mce_check_crashing_cpu(void)
{
+ unsigned int cpu = smp_processor_id();
+
if (cpu_is_offline(cpu) ||
(crashing_cpu != -1 && crashing_cpu != cpu)) {
u64 mcgstatus;
@@ -1235,7 +1237,6 @@ void noinstr do_machine_check(struct pt_regs *regs, long error_code)
DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
DECLARE_BITMAP(toclear, MAX_NR_BANKS);
struct mca_config *cfg = &mca_cfg;
- int cpu = smp_processor_id();
struct mce m, *final;
char *msg = NULL;
int worst = 0;
@@ -1264,11 +1265,6 @@ void noinstr do_machine_check(struct pt_regs *regs, long error_code)
*/
int lmce = 1;

- if (__mc_check_crashing_cpu(cpu))
- return;
-
- nmi_enter();
-
this_cpu_inc(mce_exception_count);

mce_gather_info(&m, regs);
@@ -1356,7 +1352,7 @@ void noinstr do_machine_check(struct pt_regs *regs, long error_code)
sync_core();

if (worst != MCE_AR_SEVERITY && !kill_it)
- goto out_ist;
+ return;

/* Fault was in user mode and we need to take some action */
if ((m.cs & 3) == 3) {
@@ -1373,9 +1369,6 @@ void noinstr do_machine_check(struct pt_regs *regs, long error_code)
if (!fixup_exception(regs, X86_TRAP_MC, error_code, 0))
mce_panic("Failed kernel mode recovery", &m, msg);
}
-
-out_ist:
- nmi_exit();
}
EXPORT_SYMBOL_GPL(do_machine_check);

@@ -1912,11 +1905,18 @@ static void unexpected_machine_check(struct pt_regs *regs, long error_code)
void (*machine_check_vector)(struct pt_regs *, long error_code) =
unexpected_machine_check;

-dotraplinkage notrace void do_mce(struct pt_regs *regs, long error_code)
+dotraplinkage noinstr void do_mce(struct pt_regs *regs, long error_code)
{
+ if (machine_check_vector == do_machine_check &&
+ mce_check_crashing_cpu())
+ return;
+
+ nmi_enter();
+
machine_check_vector(regs, error_code);
+
+ nmi_exit();
}
-NOKPROBE_SYMBOL(do_mce);

/*
* Called for each booted CPU to set up machine checks.
diff --git a/arch/x86/kernel/cpu/mce/p5.c b/arch/x86/kernel/cpu/mce/p5.c
index 5ee94aa..dc29f0f 100644
--- a/arch/x86/kernel/cpu/mce/p5.c
+++ b/arch/x86/kernel/cpu/mce/p5.c
@@ -25,8 +25,6 @@ static void pentium_machine_check(struct pt_regs *regs, long error_code)
{
u32 loaddr, hi, lotype;

- nmi_enter();
-
rdmsr(MSR_IA32_P5_MC_ADDR, loaddr, hi);
rdmsr(MSR_IA32_P5_MC_TYPE, lotype, hi);

@@ -39,8 +37,6 @@ static void pentium_machine_check(struct pt_regs *regs, long error_code)
}

add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
-
- nmi_exit();
}

/* Set up machine check reporting for processors with Intel style MCE: */
diff --git a/arch/x86/kernel/cpu/mce/winchip.c b/arch/x86/kernel/cpu/mce/winchip.c
index b3938c1..3f8f84b 100644
--- a/arch/x86/kernel/cpu/mce/winchip.c
+++ b/arch/x86/kernel/cpu/mce/winchip.c
@@ -19,12 +19,8 @@
/* Machine check handler for WinChip C6: */
static void winchip_machine_check(struct pt_regs *regs, long error_code)
{
- nmi_enter();
-
pr_emerg("CPU0: Machine Check Exception.\n");
add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
-
- nmi_exit();
}

/* Set up machine check reporting on the Winchip C6 series */
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