Sean Christopherson 2cdd64cbf9 KVM: Disallow binding multiple irqfds to an eventfd with a priority waiter ... Disallow binding an irqfd to an eventfd that already has a priority waiter, i.e. to an eventfd that already has an attached irqfd. KVM always operates in exclusive mode for EPOLL_IN (unconditionally returns '1'), i.e. only the first waiter will be notified. KVM already disallows binding multiple irqfds to an eventfd in a single VM, but doesn't guard against multiple VMs binding to an eventfd. Adding the extra protection reduces the pain of a userspace VMM bug, e.g. if userspace fails to de-assign before re-assigning when transferring state for intra-host migration, then the migration will explicitly fail as opposed to dropping IRQs on the destination VM. Temporarily keep KVM's manual check on irqfds.items, but add a WARN, e.g. to allow sanity checking the waitqueue enforcement. Cc: Oliver Upton <oliver.upton@linux.dev> Cc: David Matlack <dmatlack@google.com> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20250522235223.3178519-10-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>		2025-06-23 09:50:59 -07:00
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kvm	KVM: Disallow binding multiple irqfds to an eventfd with a priority waiter	2025-06-23 09:50:59 -07:00
lib	irqbypass: Require producers to pass in Linux IRQ number during registration	2025-06-20 13:52:41 -07:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00