[3.12] main/xen: security fix for XSA-360
Fixes IRQ vector leak on x86 systems running HVM guests with PCI pass through devices.
Backport of !17319 (merged) to 3.12-stable.
Fixes IRQ vector leak on x86 systems running HVM guests with PCI pass through devices.
Backport of !17319 (merged) to 3.12-stable.