linux-kernel - [PATCH] x86/xen: disable Firmware First mode for correctable memory errors

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Date:   Fri, 25 Sep 2020 12:11:48 +0200
From:   Juergen Gross <jgross@...e.com>
To:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, stable@...r.kernel.org
Subject: [PATCH] x86/xen: disable Firmware First mode for correctable memory errors

When running as Xen dom0 the kernel isn't responsible for selecting the
error handling mode, this should be handled by the hypervisor.

So disable setting FF mode when running as Xen pv guest. Not doing so
might result in boot splats like:

[    7.509696] HEST: Enabling Firmware First mode for corrected errors.
[    7.510382] mce: [Firmware Bug]: Ignoring request to disable invalid MCA bank 2.
[    7.510383] mce: [Firmware Bug]: Ignoring request to disable invalid MCA bank 3.
[    7.510384] mce: [Firmware Bug]: Ignoring request to disable invalid MCA bank 4.
[    7.510384] mce: [Firmware Bug]: Ignoring request to disable invalid MCA bank 5.
[    7.510385] mce: [Firmware Bug]: Ignoring request to disable invalid MCA bank 6.
[    7.510386] mce: [Firmware Bug]: Ignoring request to disable invalid MCA bank 7.
[    7.510386] mce: [Firmware Bug]: Ignoring request to disable invalid MCA bank 8.

Reason is that the HEST ACPI table contains the real number of MCA
banks, while the hypervisor is emulating only 2 banks for guests.

Cc: stable@...r.kernel.org
Signed-off-by: Juergen Gross <jgross@...e.com>
---
 arch/x86/xen/enlighten_pv.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 22e741e0b10c..065c049d0f3c 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1296,6 +1296,14 @@ asmlinkage __visible void __init xen_start_kernel(void)

 	xen_smp_init();

+#ifdef CONFIG_ACPI
+	/*
+	 * Disable selecting "Firmware First mode" for correctable memory
+	 * errors, as this is the duty of the hypervisor to decide.
+	 */
+	acpi_disable_cmcff = 1;
+#endif
+
 #ifdef CONFIG_ACPI_NUMA
 	/*
 	 * The pages we from Xen are not related to machine pages, so
-- 
2.26.2