linux-kernel - [PATCH v2 1/5] x86/mce: do not overwrite no_way_out if mce

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Message-Id: <20201127161819.3106432-2-gabriele.paoloni@intel.com>
Date:   Fri, 27 Nov 2020 16:18:15 +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 1/5] x86/mce: do not overwrite no_way_out if mce_end() fails

Currently if mce_end() fails 'no_way_out' is set equal to 'worst'.
'worst' is the worst severity that was found across the MCA banks
associated with the current CPU; however at this point 'no_way_out'
could have been already set by mca_start() by looking at all
severities of all CPUs that entered the MCE handler.
If mce_end() fails, check first if no_way_out is already set and,
if so, stick to it, otherwise use the local worst value.

Cc: <stable@...r.kernel.org>
Signed-off-by: Gabriele Paoloni <gabriele.paoloni@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/cpu/mce/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 4102b866e7c0..32b7099e3511 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1384,8 +1384,10 @@ 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)
-			no_way_out = worst >= MCE_PANIC_SEVERITY;
+		if (mce_end(order) < 0) {
+			if (!no_way_out)
+				no_way_out = worst >= MCE_PANIC_SEVERITY;
+		}
 	} else {
 		/*
 		 * If there was a fatal machine check we should have
-- 
2.20.1

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