irqchip: GICv3: Convert to EOImode == 1
So far, GICv3 has been used in with EOImode == 0. The effect of this
mode is to perform the priority drop and the deactivation of the
interrupt at the same time.
While this works perfectly for Linux (we only have a single priority),
it causes issues when an interrupt is forwarded to a guest, and when
we want the guest to perform the EOI itself. This is also rather
inefficient for threaded interrupts, as it forces us to hit the
distributor (which is slower, specially when using virtualization).
For this case, the GIC architecture provides EOImode == 1, where:
- A write to ICC_EOIR1_EL1 drops the priority of the interrupt and leaves
it active. Other interrupts at the same priority level can now be taken,
but the active interrupt cannot be taken again
- A write to ICC_DIR_EL1 marks the interrupt as inactive, meaning it can
now be taken again.
This patch converts the driver to this new mode when virtualization is
enabled.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
2 files changed
