Hi Zenghui, On Wed, Feb 21, 2024 at 12:30:24AM +0800, Zenghui Yu wrote: > On 2024/2/17 02:41, Oliver Upton wrote: > > Using a linked-list for LPIs is less than ideal as it of course requires > > iterative searches to find a particular entry. An xarray is a better > > data structure for this use case, as it provides faster searches and can > > still handle a potentially sparse range of INTID allocations. > > > > Start by storing LPIs in an xarray, punting usage of the xarray to a > > subsequent change. > > > > Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx> > > [..] > > > diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c > > index db2a95762b1b..c126014f8395 100644 > > --- a/arch/arm64/kvm/vgic/vgic.c > > +++ b/arch/arm64/kvm/vgic/vgic.c > > @@ -131,6 +131,7 @@ void __vgic_put_lpi_locked(struct kvm *kvm, struct vgic_irq *irq) > > return; > > list_del(&irq->lpi_list); > > + xa_erase(&dist->lpi_xa, irq->intid); > > We can get here *after* grabbing the vgic_cpu->ap_list_lock (e.g., > vgic_flush_pending_lpis()/vgic_put_irq()). And as according to vGIC's > "Locking order", we should disable interrupts before taking the xa_lock > in xa_erase() and we would otherwise see bad things like deadlock.. Nice catch! Yeah, the general intention was to disable interrupts outside of the xa_lock, however: > It's not a problem before patch #10, where we drop the lpi_list_lock and > start taking the xa_lock with interrupts enabled. Consider switching to > use xa_erase_irq() instead? I don't think this change is safe until #10, as the implied xa_unlock_irq() would re-enable interrupts before the lpi_list_lock is dropped. Or do I have wires crossed? -- Thanks, Oliver
