The patch below does not apply to the 4.16-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 339b2ae0cd5d4a58f9efe06e4ee36adbeca59228 Mon Sep 17 00:00:00 2001
From: Baoquan He bhe@redhat.com Date: Wed, 14 Feb 2018 13:46:53 +0800 Subject: [PATCH] x86/apic: Fix restoring boot IRQ mode in reboot and kexec/kdump
This is a regression fix.
Before, to fix erratum AVR31, the following commit:
522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC")
... moved the lapic_shutdown() call to after disable_IO_APIC() in the reboot and kexec/kdump code paths.
This introduced the following regression: disable_IO_APIC() not only clears the IO-APIC, but it also restores boot IRQ mode by setting the LAPIC/APIC/IMCR, calling lapic_shutdown() after disable_IO_APIC() will disable LAPIC and ruin the possible virtual wire mode setting which the code has been trying to do all along.
The consequence is that a KVM guest kernel always prints the warning below during kexec/kdump as the kernel boots up:
[ 0.001000] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/apic/apic.c:1467 setup_local_APIC+0x228/0x330 [ ........] [ 0.001000] Call Trace: [ 0.001000] apic_bsp_setup+0x56/0x74 [ 0.001000] x86_late_time_init+0x11/0x16 [ 0.001000] start_kernel+0x3c9/0x486 [ 0.001000] secondary_startup_64+0xa5/0xb0 [ ........] [ 0.001000] masked ExtINT on CPU#0
To fix this, just call clear_IO_APIC() to stop the IO-APIC where disable_IO_APIC() was called, and call restore_boot_irq_mode() to restore boot IRQ mode before a reboot or a kexec/kdump jump.
Signed-off-by: Baoquan He bhe@redhat.com Reviewed-by: Eric W. Biederman ebiederm@xmission.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: douly.fnst@cn.fujitsu.com Cc: joro@8bytes.org Cc: prarit@redhat.com Cc: stable@vger.kernel.org Cc: uobergfe@redhat.com Fixes: commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC") Link: http://lkml.kernel.org/r/20180214054656.3780-4-bhe@redhat.com [ Rewrote the changelog. ] Signed-off-by: Ingo Molnar mingo@kernel.org
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 10e74d4778a1..1f6680427ff0 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -199,9 +199,10 @@ void native_machine_crash_shutdown(struct pt_regs *regs) #ifdef CONFIG_X86_IO_APIC /* Prevent crash_kexec() from deadlocking on ioapic_lock. */ ioapic_zap_locks(); - disable_IO_APIC(); + clear_IO_APIC(); #endif lapic_shutdown(); + restore_boot_irq_mode(); #ifdef CONFIG_HPET_TIMER hpet_disable(); #endif diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index 2126b9d27c34..725624b6c0c0 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -666,7 +666,7 @@ void native_machine_shutdown(void) * Even without the erratum, it still makes sense to quiet IO APIC * before disabling Local APIC. */ - disable_IO_APIC(); + clear_IO_APIC(); #endif
#ifdef CONFIG_SMP @@ -680,6 +680,7 @@ void native_machine_shutdown(void) #endif
lapic_shutdown(); + restore_boot_irq_mode();
#ifdef CONFIG_HPET_TIMER hpet_disable();