Hello Julien,
It looks I missed answering this email. So do this now:
On 29.11.18 00:00, Julien Grall wrote:
On 28/11/2018 21:31, Andrii Anisov wrote:
From: Julien Grall <julien.gr...@arm.com>
This makes function enter_hypervisor_head() being executed with
irqs locked. This also give a fine side effect - it assures that
LRs are cleared prior to any IRQs processing, which leads to a
better (faster) IRQs processing.
Again, this need some rationale why is it faster. And how this is going
to impact the other vGIC...
With the current code, there is a chance that hypervisor performs do_IRQ()
before fetching LRs with the information about IRQs being processed by a guest.
This could happen in guest trap paths where interrupts are enabled before
`enter_hypervisor_head()` call.
Performing `do_IRQ()` prior to `vgic_sync_from_lrs()` is assumed as less
efficient than doing it vice versa for high IRQ rate use-cases with the number
of different interrupts (specific for multimedia scenarios).
- For the old vgic implementation, `vgic_sync_from_lrs()` release LRs from
processed interrupts also shortens `inflight_irqs` sorted list. So `do_IRQ()`
has better chances to write IRQ directly to LR instead of saving it into
`lr_pending` list and possibly faster insert the new IRQ into `inflight_irqs`
list.
- For the new vgic implementation, `vgic_sync_from_lrs()` fetches about
processed interrupts from LRs and shortens `ap_list`. So `do_IRQ()` could
potentially faster insert the new interrupt into `ap_list`.
--
Sincerely,
Andrii Anisov.
.
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