The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From fe6f85ca121e9c74e7490fe66b0c5aae38e332c3 Mon Sep 17 00:00:00 2001

From: Jan Beulich jbeulich@suse.com Date: Tue, 29 Oct 2019 10:34:19 +0100 Subject: [PATCH] x86/apic/32: Avoid bogus LDR warnings

The removal of the LDR initialization in the bigsmp_32 APIC code unearthed a problem in setup_local_APIC().

The code checks unconditionally for a mismatch of the logical APIC id by comparing the early APIC id which was initialized in get_smp_config() with the actual LDR value in the APIC.

Due to the removal of the bogus LDR initialization the check now can trigger on bigsmp_32 APIC systems emitting a warning for every booting CPU. This is of course a false positive because the APIC is not using logical destination mode.

Restrict the check and the possibly resulting fixup to systems which are actually using the APIC in logical destination mode.

[ tglx: Massaged changelog and added Cc stable ]

Fixes: bae3a8d3308 ("x86/apic: Do not initialize LDR and DFR for bigsmp") Signed-off-by: Jan Beulich jbeulich@suse.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/666d8f91-b5a8-1afd-7add-821e72a35f03@suse.com

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 9e2dd2b296cd..2b0faf86da1b 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1586,9 +1586,6 @@ static void setup_local_APIC(void) { int cpu = smp_processor_id(); unsigned int value; -#ifdef CONFIG_X86_32 - int logical_apicid, ldr_apicid; -#endif

if (disable_apic) { disable_ioapic_support(); @@ -1626,16 +1623,21 @@ static void setup_local_APIC(void) apic->init_apic_ldr();

#ifdef CONFIG_X86_32 - /* - * APIC LDR is initialized. If logical_apicid mapping was - * initialized during get_smp_config(), make sure it matches the - * actual value. - */ - logical_apicid = early_per_cpu(x86_cpu_to_logical_apicid, cpu); - ldr_apicid = GET_APIC_LOGICAL_ID(apic_read(APIC_LDR)); - WARN_ON(logical_apicid != BAD_APICID && logical_apicid != ldr_apicid); - /* always use the value from LDR */ - early_per_cpu(x86_cpu_to_logical_apicid, cpu) = ldr_apicid; + if (apic->dest_logical) { + int logical_apicid, ldr_apicid; + + /* + * APIC LDR is initialized. If logical_apicid mapping was + * initialized during get_smp_config(), make sure it matches + * the actual value. + */ + logical_apicid = early_per_cpu(x86_cpu_to_logical_apicid, cpu); + ldr_apicid = GET_APIC_LOGICAL_ID(apic_read(APIC_LDR)); + if (logical_apicid != BAD_APICID) + WARN_ON(logical_apicid != ldr_apicid); + /* Always use the value from LDR. */ + early_per_cpu(x86_cpu_to_logical_apicid, cpu) = ldr_apicid; + } #endif

/*