• Marc Zyngier's avatar
    KVM: arm64: vgic-v4: Plug race between non-residency and v4.1 doorbell · a3f574cd
    Marc Zyngier authored
    When making a vPE non-resident because it has hit a blocking WFI,
    the doorbell can fire at any time after the write to the RD.
    Crucially, it can fire right between the write to GICR_VPENDBASER
    and the write to the pending_last field in the its_vpe structure.
    
    This means that we would overwrite pending_last with stale data,
    and potentially not wakeup until some unrelated event (such as
    a timer interrupt) puts the vPE back on the CPU.
    
    GICv4 isn't affected by this as we actively mask the doorbell on
    entering the guest, while GICv4.1 automatically manages doorbell
    delivery without any hypervisor-driven masking.
    
    Use the vpe_lock to synchronize such update, which solves the
    problem altogether.
    
    Fixes: ae699ad3 ("irqchip/gic-v4.1: Move doorbell management to the GICv4 abstraction layer")
    Reported-by: default avatarZenghui Yu <yuzenghui@huawei.com>
    Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
    a3f574cd
irq-gic-v3-its.c 133 KB