[x86] boot/smp: Don't try to poke disabled/non-existent APIC

Closes: #841850

debian/changelog

@@ -1,10 +1,15 @@
 linux (4.8.4-1~exp2) UNRELEASED; urgency=medium
 
+  [ Ben Hutchings ]
   * cpufreq: Re-enable CPU_FREQ_STAT, which can no longer be modular
   * [armhf] dts: imx53: add support for USB armory board (Closes: #840137)
   * kconfig: Renumber SYMBOL_NEW, fixing regression of allnoconfig
     (Closes: #841357)
 
+  [ Salvatore Bonaccorso ]
+  * [x86] boot/smp: Don't try to poke disabled/non-existent APIC
+    (Closes: #841850)
+
  -- Ben Hutchings <ben@decadent.org.uk>  Mon, 24 Oct 2016 02:25:26 +0100
 
 linux (4.8.4-1~exp1) experimental; urgency=medium

debian/patches/bugfix/x86/x86-boot-smp-Don-t-try-to-poke-disabled-non-existent.patch

@@ -0,0 +1,74 @@
+From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
+Date: Sat, 22 Oct 2016 05:18:04 +0300
+Subject: x86/boot/smp: Don't try to poke disabled/non-existent APIC
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+Origin: https://git.kernel.org/linus/ff8560512b8d4b7ca3ef4fd69166634ac30b2525
+Bug-Debian: https://bugs.debian.org/841850
+
+Apparently trying to poke a disabled or non-existent APIC
+leads to a box that doesn't even boot. Let's not do that.
+
+No real clue if this is the right fix, but at least my
+P3 machine boots again.
+
+Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
+Cc: Andy Lutomirski <luto@kernel.org>
+Cc: Borislav Petkov <bp@alien8.de>
+Cc: Borislav Petkov <bp@suse.de>
+Cc: Brian Gerst <brgerst@gmail.com>
+Cc: Denys Vlasenko <dvlasenk@redhat.com>
+Cc: Eric Biederman <ebiederm@xmission.com>
+Cc: H. Peter Anvin <hpa@zytor.com>
+Cc: Jiri Olsa <jolsa@redhat.com>
+Cc: Josh Poimboeuf <jpoimboe@redhat.com>
+Cc: Juergen Gross <jgross@suse.com>
+Cc: Len Brown <len.brown@intel.com>
+Cc: Linus Torvalds <torvalds@linux-foundation.org>
+Cc: Peter Zijlstra <peterz@infradead.org>
+Cc: Prarit Bhargava <prarit@redhat.com>
+Cc: Thomas Gleixner <tglx@linutronix.de>
+Cc: Yinghai Lu <yinghai@kernel.org>
+Cc: dyoung@redhat.com
+Cc: kexec@lists.infradead.org
+Cc: stable@vger.kernel.org
+Fixes: 2a51fe083eba ("arch/x86: Handle non enumerated CPU after physical hotplug")
+Link: http://lkml.kernel.org/r/1477102684-5092-1-git-send-email-ville.syrjala@linux.intel.com
+Signed-off-by: Ingo Molnar <mingo@kernel.org>
+---
+ arch/x86/kernel/smpboot.c | 16 +++++++++-------
+ 1 file changed, 9 insertions(+), 7 deletions(-)
+
+diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
+index 951f093..42f5eb7 100644
+--- a/arch/x86/kernel/smpboot.c
++++ b/arch/x86/kernel/smpboot.c
+@@ -1409,15 +1409,17 @@ __init void prefill_possible_map(void)
+ 
+ 	/* No boot processor was found in mptable or ACPI MADT */
+ 	if (!num_processors) {
+-		int apicid = boot_cpu_physical_apicid;
+-		int cpu = hard_smp_processor_id();
++		if (boot_cpu_has(X86_FEATURE_APIC)) {
++			int apicid = boot_cpu_physical_apicid;
++			int cpu = hard_smp_processor_id();
+ 
+-		pr_warn("Boot CPU (id %d) not listed by BIOS\n", cpu);
++			pr_warn("Boot CPU (id %d) not listed by BIOS\n", cpu);
+ 
+-		/* Make sure boot cpu is enumerated */
+-		if (apic->cpu_present_to_apicid(0) == BAD_APICID &&
+-		    apic->apic_id_valid(apicid))
+-			generic_processor_info(apicid, boot_cpu_apic_version);
++			/* Make sure boot cpu is enumerated */
++			if (apic->cpu_present_to_apicid(0) == BAD_APICID &&
++			    apic->apic_id_valid(apicid))
++				generic_processor_info(apicid, boot_cpu_apic_version);
++		}
+ 
+ 		if (!num_processors)
+ 			num_processors = 1;
+-- 
+2.10.1
+

debian/patches/series

@@ -48,6 +48,7 @@ debian/fanotify-taint-on-use-of-fanotify_access_permissions.patch
 # Arch bug fixes
 bugfix/powerpc/powerpc-xmon-don-t-use-ld-on-32-bit.patch
 bugfix/arm64/arm64-mm-limit-task_size_64-for-compatibility.patch
+bugfix/x86/x86-boot-smp-Don-t-try-to-poke-disabled-non-existent.patch
 
 # Arch features
 features/mips/MIPS-increase-MAX-PHYSMEM-BITS-on-Loongson-3-only.patch