linux-kernel - [PATCH] x86/MCE/AMD: Allow thresholding interface updates after init

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Date:   Tue, 7 Dec 2021 19:30:28 +0000
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     <linux-edac@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <tony.luck@...el.com>,
        <x86@...nel.org>, <Smita.KoralahalliChannabasappa@....com>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: [PATCH] x86/MCE/AMD: Allow thresholding interface updates after init

Changes to the AMD Thresholding sysfs code prevents sysfs writes from
updating the underlying registers once CPU init is completed, i.e.
"threshold_banks" is set.

Allow the registers to be updated if the thresholding interface is
already initialized or if in the init path. Use the "set_lvt_off" value
to indicate if running in the init path, since this value is only set
during init.

Fixes: a037f3ca0ea0 ("x86/mce/amd: Make threshold bank setting hotplug robust")
Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
---
 arch/x86/kernel/cpu/mce/amd.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 2eadc7c4c902..408c9546ea0b 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -400,8 +400,12 @@ static void threshold_restart_bank(void *_tr)
 	struct thresh_restart *tr = _tr;
 	u32 hi, lo;
 
-	/* sysfs write might race against an offline operation */
-	if (this_cpu_read(threshold_banks))
+	/*
+	 * sysfs write might race against an offline operation.
+	 * Prevent register writes if threshold_banks are not set and this is
+	 * not called from the init path as indicated by "set_lvt_off".
+	 */
+	if (!(this_cpu_read(threshold_banks) || tr->set_lvt_off))
 		return;
 
 	rdmsr(tr->b->address, lo, hi);
-- 
2.25.1