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Re: [Xen-devel] [PATCH for-4.12] pvh/dom0: fix deadlock in GSI mapping

On Mon, Jan 28, 2019 at 08:30:02AM -0700, Jan Beulich wrote:
> >>> On 28.01.19 at 15:22, <roger.pau@xxxxxxxxxx> wrote:
> > In order to solve it move the vioapic_hwdom_map_gsi outside of the
> > locked region in vioapic_write_redirent. vioapic_hwdom_map_gsi will
> > not access any of the vioapic fields, so there's no need to call the
> > function holding the hvm.irq_lock.
> True, but you also move the code across a vioapic_deliver()
> invocation. Is that delivery going to work when
> vioapic_hwdom_map_gsi() gets invoked only afterwards?

Yes, that vioapic_deliver will only get invoked when there's a pending
gsi (hvm_irq->gsi_assert_count[idx] > 0), and that can only happen
once the hardware gsi is bound to dom0 and the hvm.irq_lock has been
released, so that the dpci softirq can increase the gsi assert count.

Thanks, Roger.

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