From ea7bdc65bca8cf837a63e0ff7b75daed83222511 Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Mon, 27 Jan 2014 20:14:06 +0100 Subject: [PATCH] x86/apic: Plug racy xAPIC access of CPU hotplug code apic_icr_write() and its users in smpboot.c were apparently written under the assumption that this code would only run during early boot. But nowadays we also execute it when onlining a CPU later on while the system is fully running. That will make wakeup_cpu_via_init_nmi and, thus, also native_apic_icr_write run in plain process context. If we migrate the caller to a different CPU at the wrong time or interrupt it and write to ICR/ICR2 to send unrelated IPIs, we can end up sending INIT, SIPI or NMIs to wrong CPUs. Fix this by disabling interrupts during the write to the ICR halves and disable preemption around waiting for ICR availability and using it. Signed-off-by: Jan Kiszka Tested-By: Igor Mammedov Link: http://lkml.kernel.org/r/52E6AFFE.3030004@siemens.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/apic/apic.c | 4 ++++ arch/x86/kernel/smpboot.c | 11 +++++++++-- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index f824d697db19..53e20531470e 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -286,8 +286,12 @@ u32 native_safe_apic_wait_icr_idle(void) void native_apic_icr_write(u32 low, u32 id) { + unsigned long flags; + + local_irq_save(flags); apic_write(APIC_ICR2, SET_APIC_DEST_FIELD(id)); apic_write(APIC_ICR, low); + local_irq_restore(flags); } u64 native_apic_icr_read(void) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index c77acc69ecf6..60179ec39d4c 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -702,11 +702,15 @@ wakeup_cpu_via_init_nmi(int cpu, unsigned long start_ip, int apicid, int id; int boot_error; + preempt_disable(); + /* * Wake up AP by INIT, INIT, STARTUP sequence. */ - if (cpu) - return wakeup_secondary_cpu_via_init(apicid, start_ip); + if (cpu) { + boot_error = wakeup_secondary_cpu_via_init(apicid, start_ip); + goto out; + } /* * Wake up BSP by nmi. @@ -726,6 +730,9 @@ wakeup_cpu_via_init_nmi(int cpu, unsigned long start_ip, int apicid, boot_error = wakeup_secondary_cpu_via_nmi(id, start_ip); } +out: + preempt_enable(); + return boot_error; } -- 2.20.1