genirq/msi: Activate Multi-MSI early when MSI_FLAG_ACTIVATE_EARLY is set

When MSI_FLAG_ACTIVATE_EARLY is set (which is the case for PCI),
we perform the activation of the interrupt (which in the case of
PCI results in the endpoint being programmed) as soon as the
interrupt is allocated.

But it appears that this is only done for the first vector,
introducing an inconsistent behaviour for PCI Multi-MSI.

Fix it by iterating over the number of vectors allocated to
each MSI descriptor. This is easily achieved by introducing
a new "for_each_msi_vector" iterator, together with a tiny
bit of refactoring.

Fixes: f3b0946d629c ("genirq/msi: Make sure PCI MSIs are activated early")
Reported-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
2 files changed