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| author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2019-04-02 10:02:15 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-05-17 15:19:39 +0200 |
| commit | 958a01dab8e02fc49f4fd619fad8c82a1108afdb (patch) | |
| tree | cdd63e978ad652d0d33686b2804a7817125d7468 /hw/char/serial-pci-multi.c | |
| parent | 29de2804014097f8d0e6eaec3318164405afe317 (diff) | |
ioapic: allow buggy guests mishandling level-triggered interrupts to make progress
It was found that Hyper-V 2016 on KVM in some configurations (q35 machine +
piix4-usb-uhci) hangs on boot. Root-cause was that one of Hyper-V
level-triggered interrupt handler performs EOI before fixing the cause of
the interrupt. This results in IOAPIC keep re-raising the level-triggered
interrupt after EOI because irq-line remains asserted.
Gory details: https://www.spinics.net/lists/kvm/msg184484.html
(the whole thread).
Turns out we were dealing with similar issues before; in-kernel IOAPIC
implementation has commit 184564efae4d ("kvm: ioapic: conditionally delay
irq delivery duringeoi broadcast") which describes a very similar issue.
Steal the idea from the above mentioned commit for IOAPIC implementation in
QEMU. SUCCESSIVE_IRQ_MAX_COUNT, delay and the comment are borrowed as well.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20190402080215.10747-1-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'hw/char/serial-pci-multi.c')
0 files changed, 0 insertions, 0 deletions