vtnet IFF_NEEDSEPOCH?

[Gleb Smirnoff]

On Tue, Feb 18, 2020 at 10:52:09AM +0100, Kristof Provost wrote:
K> Hi,
K> 
K> I’ve been playing around with a risc-v qemu image, and run into this panic
K> with vtnet:
K> 
K> 	DHCPDISCOVER on vtnet0 to 255.255.255.255 port 67 interval 5
K> 	panic: Assertion in_epoch(net_epoch_preempt) failed at
K> /usr/src/sys/net/netisr.c:1093
K> 	cpuid = 0
K> 	time = 1581981733
K> 	KDB: stack backtrace:
K> 	db_trace_self() at db_trace_self
K> 	db_fetch_ksymtab() at db_fetch_ksymtab+0x12a
K> 	kdb_backtrace() at kdb_backtrace+0x2c
K> 	vpanic() at vpanic+0x144
K> 	panic() at panic+0x26
K> 	netisr_dispatch_src() at netisr_dispatch_src+0x3c0
K> 	netisr_dispatch() at netisr_dispatch+0x10
K> 	ether_ifattach() at ether_ifattach+0x2fa
K> 	vtmmio_attach() at vtmmio_attach+0x490c
K> 	vtmmio_attach() at vtmmio_attach+0x4624
K> 	vtmmio_attach() at vtmmio_attach+0x544a
K> 	virtqueue_intr() at virtqueue_intr+0xc
K> 	vtmmio_attach() at vtmmio_attach+0x2008
K> 	db_dump_intr_event() at db_dump_intr_event+0x730
K> 	fork_exit() at fork_exit+0x68
K> 	fork_trampoline() at fork_trampoline+0xa
K> 	KDB: enter: panic
K> 	[ thread pid 12 tid 100023 ]
K> 	Stopped at      kdb_enter+0x44: sd      zero,0(a0)
K> 	db>
K> 
K> It seems pretty clear that the vtmmio path doesn’t enter epoch before it
K> runs the vtnet_attach() code.
K> On the other hand, I run vtnet CURRENT guests in bhyve, and don’t see this
K> panic. In that case it lives on top of PCI rather than mmio, but I don’t
K> see why/where that’d enter epoch.

The transition from ether_ifattach to netisr_dispatch looks strange.
Is that something run trough EVENTHANDLER_INVOKE?

Can you please print in kgdb?

> list *ether_ifattach+0x2fa


-- 
Gleb Smirnoff