linux-kernel - [PATCH 2/4] x86/mce: move the mce_panic() call and kill

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Message-Id: <20201118151552.1412-3-gabriele.paoloni@intel.com>
Date:   Wed, 18 Nov 2020 15:15:50 +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 2/4] x86/mce: move the mce_panic() call and kill_it assignments at 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 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@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.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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