lost interrupts when running sabrelite images (v4.15+) in qemu

[Guenter Roeck <linux@roeck-us.net>]

Hi,

since v4.15, I get the following runtime warning when running sabrelite images
in qemu.

irq 65: nobody cared (try booting with the "irqpoll" option)
...
handlers:
[<26292474>] fec_pps_interrupt
Disabling IRQ #65
fec 2188000.ethernet (unnamed net_device) (uninitialized): MDIO read timeout

Bisect points to commit 4ad1ceec05e491 ("net: fec: Let fec_ptp have its
own interrupt routine"). Analysis shows that platform_irq_count()
returns 2, which is reduced to 1 by fec_enet_get_irq_cnt().
If I let fec_enet_get_irq_cnt() return 2, the problem is gone.
Reverting commit 4ad1ceec05e491 also fixes the problem.

Bisect log is attached.

Guenter

----
# bad: [d8a5b80568a9cb66810e75b182018e9edb68e8ff] Linux 4.15
# good: [bebc6082da0a9f5d47a1ea2edc099bf671058bd4] Linux 4.14
git bisect start 'v4.15' 'v4.14'
# bad: [5d352e69c60e54b5f04d6e337a1d2bf0dbf3d94a] Merge tag 'media/v4.15-1' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
git bisect bad 5d352e69c60e54b5f04d6e337a1d2bf0dbf3d94a
# good: [4e4510fec4af08ead21f6934c1410af1f19a8cad] Merge tag 'sound-4.15-rc1' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
git bisect good 4e4510fec4af08ead21f6934c1410af1f19a8cad
# good: [9fb7bd77d11ab03b4a969279de9f54d8fd6fe988] mlxsw: spectrum_ipip: Split accessor functions
git bisect good 9fb7bd77d11ab03b4a969279de9f54d8fd6fe988
# bad: [22714a2ba4b55737cd7d5299db7aaf1fa8287354] Merge branch 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
git bisect bad 22714a2ba4b55737cd7d5299db7aaf1fa8287354
# bad: [f6b3716dcdcd1a4c3fa05ecb6ab0a1e52b6785d0] Merge branch 'net-devname_alloc_cleanups'
git bisect bad f6b3716dcdcd1a4c3fa05ecb6ab0a1e52b6785d0
# bad: [f938daeee95eb36ef6b431bf054a5cc6cdada112] net/mlx5e: CHECKSUM_COMPLETE offload for VLAN/QinQ packets
git bisect bad f938daeee95eb36ef6b431bf054a5cc6cdada112
# good: [6c49b5e26004eef86e7a47093a53be290554351c] Merge branch 'dsa-parsing-stage'
git bisect good 6c49b5e26004eef86e7a47093a53be290554351c
# bad: [ec5c91c6ca8b2d5ca6edfc968dbfeeaae4ed5572] net: dsa: lan9303: Replace msleep(1) with usleep_range()
git bisect bad ec5c91c6ca8b2d5ca6edfc968dbfeeaae4ed5572
# good: [fffcefe967a02997be7a296a4f0766b29dcd1a67] ipv6: addrconf: fix a lockdep splat
git bisect good fffcefe967a02997be7a296a4f0766b29dcd1a67
# bad: [aaf151b9e68101b03ba42d581e8a424bdd0110fe] bpf: Rename tcp_bbf.readme to tcp_bpf.readme
git bisect bad aaf151b9e68101b03ba42d581e8a424bdd0110fe
# bad: [3e29cd0e6563d5fefd59e7225750ee9922f2dad5] xdp: Sample xdp program implementing ip forward
git bisect bad 3e29cd0e6563d5fefd59e7225750ee9922f2dad5
# good: [0cf737808ae7cb25e952be619db46b9147a92f46] hv_netvsc: netvsc_teardown_gpadl() split
git bisect good 0cf737808ae7cb25e952be619db46b9147a92f46
# good: [ca1b17b7e843123f5a1e4c8bd2d7b6596ffe6e93] Merge branch 'hv_netvsc-fix-a-hang-on-channel-mtu-changes'
git bisect good ca1b17b7e843123f5a1e4c8bd2d7b6596ffe6e93
# bad: [4ad1ceec05e49175d0f967cc87628101e79176f6] net: fec: Let fec_ptp have its own interrupt routine
git bisect bad 4ad1ceec05e49175d0f967cc87628101e79176f6
# first bad commit: [4ad1ceec05e49175d0f967cc87628101e79176f6] net: fec: Let fec_ptp have its own interrupt routine