linux-kernel - [tip:x86/apic] x86/apic: Soft disable APIC before initializing it

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-2640da4cccf5cc613bf26f0998b9e340f4b5f69c@git.kernel.org>
Date:   Thu, 25 Jul 2019 07:22:09 -0700
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de,
        hpa@...or.com, peterz@...radead.org
Subject: [tip:x86/apic] x86/apic: Soft disable APIC before initializing it

Commit-ID:  2640da4cccf5cc613bf26f0998b9e340f4b5f69c
Gitweb:     https://git.kernel.org/tip/2640da4cccf5cc613bf26f0998b9e340f4b5f69c
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Mon, 22 Jul 2019 20:47:08 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 25 Jul 2019 16:11:56 +0200

x86/apic: Soft disable APIC before initializing it

If the APIC was already enabled on entry of setup_local_APIC() then
disabling it soft via the SPIV register makes a lot of sense.

That masks all LVT entries and brings it into a well defined state.

Otherwise previously enabled LVTs which are not touched in the setup
function stay unmasked and might surprise the just booting kernel.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20190722105219.068290579@linutronix.de

---
 arch/x86/kernel/apic/apic.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index fa0846d4e000..621992de49ee 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1522,6 +1522,14 @@ static void setup_local_APIC(void)
 		return;
 	}
 
+	/*
+	 * If this comes from kexec/kcrash the APIC might be enabled in
+	 * SPIV. Soft disable it before doing further initialization.
+	 */
+	value = apic_read(APIC_SPIV);
+	value &= ~APIC_SPIV_APIC_ENABLED;
+	apic_write(APIC_SPIV, value);
+
 #ifdef CONFIG_X86_32
 	/* Pound the ESR really hard over the head with a big hammer - mbligh */
 	if (lapic_is_integrated() && apic->disable_esr) {