On 24.11.2022 10:06, Roger Pau Monné wrote: > On Thu, Nov 24, 2022 at 09:42:40AM +0100, Roger Pau Monné wrote: >> On Thu, Nov 24, 2022 at 08:59:00AM +0100, Jan Beulich wrote: >>> - problematic wrt evtchn_upcall_pending, once set, preventing event >>> injection later on. >>> As you may have inferred already, I'm inclined to suggest to drop the >>> the is_vcpu_online() check from hvm_set_callback_via(). >>> >>> One related question here is whether vlapic_do_init() shouldn't have >>> the non-architectural side effect of clearing evtchn_upcall_pending. >>> While this again violates the principle of the hypervisor only ever >>> setting that bit, it would deal with the risk of no further event >>> injection once the flag is set, considering that vlapic_do_init() >>> clears IRR (and ISR). >> >> That would seem sensible to me, and was kind of what I was suggesting >> in: >> >> https://lore.kernel.org/xen-devel/Y3eO0bMKRPYJc2yQ@Air-de-Roger/ > > Another option would be for vcpu_mark_events_pending() to > unconditionally call hvm_assert_evtchn_irq() regardless of the state > of evtchn_upcall_pending.
I think you said so before, and ... > This will create some spurious events. ... I continue to be afraid of s/some/many/. This event delivery is meant to be kind of edge triggered, and I think it is a reasonable model to treat the flag going from 0 to 1 as the "edge". Jan
