linux-kernel - [PATCH v2 2/5] x86/mce: move the mce_panic() call and 'kill

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Date:   Fri, 27 Nov 2020 16:18:16 +0000
From:   Gabriele Paoloni <gabriele.paoloni@...el.com>
To:     tony.luck@...el.com, bp@...en8.de, tglx@...utronix.de,
        mingo@...hat.com, x86@...nel.org, hpa@...or.com,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     gabriele.paoloni@...el.com, linux-safety@...ts.elisa.tech
Subject: [PATCH v2 2/5] x86/mce: move the mce_panic() call and 'kill_it' assignments to the right places

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:
- improve readibility by moving the conditional evaluation of
tolerant up to when kill_it is set first;
- move the mce_panic() call up into the statement where mce_end()
fails.

Signed-off-by: Gabriele Paoloni <gabriele.paoloni@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/cpu/mce/core.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 32b7099e3511..50e9b0893a92 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.
@@ -1387,6 +1386,12 @@ noinstr void do_machine_check(struct pt_regs *regs)
 		if (mce_end(order) < 0) {
 			if (!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 {
 		/*
@@ -1403,15 +1408,6 @@ 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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