All of
 help / color / mirror / Atom feed
From: tip-bot for Thomas Gleixner <>
Subject: [tip:x86/urgent] x86/smpboot: Init apic mapping before usage
Date: Sat, 29 Oct 2016 05:04:21 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <alpine.DEB.2.20.1610282114380.5053@nanos>

Commit-ID:  0c524f819683e9f1c165d571256a9023b56f1f0c
Author:     Thomas Gleixner <>
AuthorDate: Sat, 29 Oct 2016 13:42:42 +0200
Committer:  Thomas Gleixner <>
CommitDate: Sat, 29 Oct 2016 13:58:07 +0200

x86/smpboot: Init apic mapping before usage

The recent changes, which forced the registration of the boot cpu on UP
systems, which do not have ACPI tables, have been fixed for systems w/o
local APIC, but left a wreckage for systems which have neither ACPI nor
mptables, but the CPU has an APIC, e.g. virtualbox.

The boot process crashes in prefill_possible_map() as it wants to register
the boot cpu, which needs to access the local apic, but the local APIC is
not yet mapped.

There is no reason why init_apic_mapping() can't be invoked before
prefill_possible_map(). So instead of playing another silly early mapping
game, as the ACPI/mptables code does, we just move init_apic_mapping()
before the call to prefill_possible_map().

In hindsight, I should have noticed that combination earlier.

Sorry for the churn (also in stable)!

Fixes: ff8560512b8d ("x86/boot/smp: Don't try to poke disabled/non-existent APIC")
Reported-and-debugged-by: Michal Necasek <>
Reported-and-tested-by: Wolfgang Bauer <>
Cc: Borislav Petkov <>
Signed-off-by: Thomas Gleixner <>
 arch/x86/kernel/setup.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index bbfbca5..7be097e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1221,11 +1221,16 @@ void __init setup_arch(char **cmdline_p)
+	/*
+	 * Systems w/o ACPI and mptables might not have it mapped the local
+	 * APIC yet, but it prefill_possible_map() might need to access it.
+	 */
+	init_apic_mappings();
-	init_apic_mappings();

  parent reply	other threads:[~2016-10-29 12:07 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-28 18:52 4.8.2 not booting in 32-bit VM without I/O-APIC Michal Necasek
2016-10-28 19:00 ` Thomas Gleixner
2016-10-28 19:34   ` Thomas Gleixner
2016-10-29 10:18     ` Borislav Petkov
2016-10-29 12:04     ` tip-bot for Thomas Gleixner [this message]
2016-10-29 12:06     ` [tip:x86/urgent] x86/smpboot: Init apic mapping before usage tip-bot for Thomas Gleixner

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [tip:x86/urgent] x86/smpboot: Init apic mapping before usage' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.