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

[v***@linux.intel.com]

From: Ville Syrjälä <***@linux.intel.com>

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.

Cc: ***@vger.kernel.org
Cc: Ingo Molnar <***@redhat.com>
Cc: "H. Peter Anvin" <***@zytor.com>
Cc: ***@kernel.org
Cc: Prarit Bhargava <***@redhat.com>
Cc: Peter Zijlstra <***@infradead.org>
Cc: Len Brown <***@intel.com>
Cc: Borislav Petkov <***@suse.de>
Cc: Andi Kleen <***@linux.intel.com>
Cc: Jiri Olsa <***@redhat.com>
Cc: Juergen Gross <***@suse.com>
Cc: ***@redhat.com
Cc: Eric Biederman <***@xmission.com>
Cc: ***@lists.infradead.org
Cc: Thomas Gleixner <***@linutronix.de>
Fixes: 2a51fe083eba ("arch/x86: Handle non enumerated CPU after physical hotplug")
Signed-off-by: Ville Syrjälä <***@linux.intel.com>
---
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 951f093a96fe..42f5eb7b4f6c 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;

[Prarit Bhargava]

Post by v***@linux.intel.com
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.
Fixes: 2a51fe083eba ("arch/x86: Handle non enumerated CPU after physical hotplug")
---
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 951f093a96fe..42f5eb7b4f6c 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)) {

It looks okay to gate on X86_FEATURE_APIC, but not sure if it should be

cpu_has(&cpu_data(0), X86_FEATURE_APIC)

since smp_store_boot_cpu_info() was already called.

tglx?

P.

Post by v***@linux.intel.com
+ 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;