On 15.8.2020 0.38, Ashok Raj wrote: > When offlining CPU's, fixup_irqs() migrates all interrupts away from the > outgoing CPU to an online CPU. Its always possible the device sent an > interrupt to the previous CPU destination. Pending interrupt bit in IRR in > lapic identifies such interrupts. apic_soft_disable() will not capture any > new interrupts in IRR. This causes interrupts from device to be lost during > cpu offline. The issue was found when explicitly setting MSI affinity to a > CPU and immediately offlining it. It was simple to recreate with a USB > ethernet device and doing I/O to it while the CPU is offlined. Lost > interrupts happen even when Interrupt Remapping is enabled. > > Current code does apic_soft_disable() before migrating interrupts. > > native_cpu_disable() > { > ... > apic_soft_disable(); > cpu_disable_common(); > --> fixup_irqs(); // Too late to capture anything in IRR. > } > > Just fliping the above call sequence seems to hit the IRR checks > and the lost interrupt is fixed for both legacy MSI and when > interrupt remapping is enabled. > > > Fixes: 60dcaad5736f ("x86/hotplug: Silence APIC and NMI when CPU is dead") > Link: https://lore.kernel.org/lkml/875zdarr4h....@nanos.tec.linutronix.de/ > Signed-off-by: Ashok Raj <ashok....@intel.com> > > To: linux-kernel@vger.kernel.org > To: Thomas Gleixner <t...@linutronix.de> > Cc: Sukumar Ghorai <sukumar.gho...@intel.com> > Cc: Srikanth Nandamuri <srikanth.nandam...@intel.com> > Cc: Evan Green <evgr...@chromium.org> > Cc: Mathias Nyman <mathias.ny...@linux.intel.com> > Cc: Bjorn Helgaas <bhelg...@google.com> > Cc: sta...@vger.kernel.org > ---
This fixes the lost xhci interrupt for me. Before this patch a msi interupt was lost after ~200 cycles of toggling CPUs offline/online under heavy usb traffic. With this patch I ran 3x2000 cycles without any issues (Comet lake, patch on top of 5.8) Tried both with and without CONFIG_IRQ_REMAP. No issues seen. Tested-by: Mathias Nyman <mathias.ny...@linux.intel.com>