339b2ae0cd
This is a regression fix. Before, to fix erratum AVR31, the following commit:522e664644("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: commit522e664644("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>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.