[linux-safety] [PATCH 2/4] x86/mce: move the mce_panic() call and kill_it assignments at the right places

Paoloni, Gabriele
2020-11-18T15:16:09Z

Right now for local MCEs we panic(),if needed, right after lmce is
set. For global MCEs mce_reign() takes care of calling mce_panic().
Hence this patch:
- improves readibility by moving the conditional evaluation of
tolerant up to when kill_it is set first
- moves the mce_panic() call up into the statement where mce_end()
fails

Signed-off-by: Gabriele Paoloni <gabriele.paoloni@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/mce/core.c | 21 +++++++++------------
1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index b990892c6766..e025ff04438f 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1350,8 +1350,7 @@ noinstr void do_machine_check(struct pt_regs *regs)
* severity is MCE_AR_SEVERITY we have other options.
*/
if (!(m.mcgstatus & MCG_STATUS_RIPV))
- kill_it = 1;
-
+ kill_it = (cfg->tolerant == 3) ? 0 : 1;
/*
* Check if this MCE is signaled to only this logical processor,
* on Intel, Zhaoxin only.
@@ -1384,8 +1383,15 @@ noinstr void do_machine_check(struct pt_regs *regs)
* When there's any problem use only local no_way_out state.
*/
if (!lmce) {
- if (mce_end(order) < 0)
+ if (mce_end(order) < 0) {
no_way_out = no_way_out ? no_way_out : worst >= MCE_PANIC_SEVERITY;
+ /*
+ * mce_reign() has probably failed hence evaluate if we need
+ * to panic
+ */
+ if (no_way_out && mca_cfg.tolerant < 3)
+ mce_panic("Fatal machine check on current CPU", &m, msg);
+ }
} else {
/*
* If there was a fatal machine check we should have
@@ -1401,15 +1407,6 @@ noinstr void do_machine_check(struct pt_regs *regs)
}
}

- /*
- * If tolerant is at an insane level we drop requests to kill
- * processes and continue even when there is no way out.
- */
- if (cfg->tolerant == 3)
- kill_it = 0;
- else if (no_way_out)
- mce_panic("Fatal machine check on current CPU", &m, msg);
-
if (worst > 0)
irq_work_queue(&mce_irq_work);

--
2.20.1

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