port-arm/55532: kernel panic with ena on AWS a1.2xlarge

[coypu%sdf.org@localhost]

>Number:         55532
>Category:       port-arm
>Synopsis:       kernel panic with ena on AWS a1.2xlarge
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-arm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Aug 02 19:05:00 +0000 2020
>Originator:     coypu
>Release:        NetBSD 9.99.69
>Organization:
>Environment:
NetBSD 9.99.69 (GENERIC64) #0: Fri Jul 31 20:08:08 UTC 2020
>Description:
[ 7463.6321023] panic: mbuf 0xffff000068ea8290 already freed
[ 7463.6321023] cpu0: Begin traceback...
[ 7463.6321023] trace fp ffffc0014dc17850
[ 7463.6321023] fp ffffc0014dc17870 vpanic() at ffffc000004b8884 netbsd:vpanic+0x15c
[ 7463.6321023] fp ffffc0014dc178e0 panic() at ffffc000004b897c netbsd:panic+0x44
[ 7463.6321023] fp ffffc0014dc17970 m_free() at ffffc000004e7620 netbsd:m_free+0x98
[ 7463.6321023] fp ffffc0014dc17990 m_freem.part.7() at ffffc000004e83f0 netbsd:m_freem.part.7+0x8
[ 7463.6321023] fp ffffc0014dc179a0 ena_tx_cleanup() at ffffc000000de2a4 netbsd:ena_tx_cleanup+0xfc
[ 7463.6321023] fp ffffc0014dc17a70 ena_handle_msix() at ffffc000000de644 netbsd:ena_handle_msix+0x8c
[ 7463.6321023] fp ffffc0014dc17ae0 pic_dispatch() at ffffc00000002814 netbsd:pic_dispatch+0xa4
[ 7463.6321023] fp ffffc0014dc17b10 gicv3_irq_handler() at ffffc00000006c44 netbsd:gicv3_irq_handler+0xe4
[ 7463.6321023] fp ffffc0014dc17b80 interrupt() at ffffc0000008d03c netbsd:interrupt+0x2c
[ 7463.6321023] tf ffffc0014dc17ba0 el1_trap() at ffffc0000008a7d8 netbsd:el1_trap
[ 7463.6321023] ---- trapframe 0xffffc0014dc17ba0 (304 bytes) ----
[ 7463.6321023]     pc=ffffc0000008a868,   spsr=0000000020000005
[ 7463.6321023]    esr=000000009200004f,    far=0000f9a332ac0036
[ 7463.6321023]     x0=0000000000000001,     x1=00000000fffffffe
[ 7463.6321023]     x2=0000000000000000,     x3=0000000000000000
[ 7463.6321023]     x4=ffffc00000c2ec5c,     x5=0000000000000005
[ 7463.6321023]     x6=0000000000000005,     x7=00000000000000ab
[ 7463.6321023]     x8=ffffc00000c2e880,     x9=0000000000000001
[ 7463.6321023]    x10=0000f9a332e3d000,    x11=0000f9a332de06c0
[ 7463.6321023]    x12=0000000000f6d070,    x13=00000000010d0668
[ 7463.6321023]    x14=0000000000000024,    x15=0000f9a332e55888
[ 7463.6321023]    x16=0000f9a3328008c0,    x17=0000f9a332dd7120
[ 7463.6321023]    x18=0000f9a332e4bd3a,    x19=0000fffffff6c3c0
[ 7463.6321023]    x20=0000fffffff6c2d0,    x21=0000f9a332d6dc10
[ 7463.6321023]    x22=0000000080000000,    x23=000000009200004f
[ 7463.6321023]    x24=0000f9a332ac0036,    x25=0000000000000003
[ 7463.6321023]    x26=000000000000007b,    x27=0000f9a33306c180
[ 7463.6321023]    x28=000000000000002e, fp=x29=ffffc0014dc17ed0
[ 7463.6321023] lr=x30=ffffc0000008a864,     sp=ffffc0014dc17ed0
[ 7463.6321023] ------------------------------------------------
[ 7463.6321023] fp ffffc0014dc17ed0 el0_trap_exit() at ffffc0000008a868 netbsd:el0_trap_exit+0x20
[ 7463.6321023] cpu0: End traceback...
Stopped in pid 26315.26315 (make) at    netbsd:cpu_Debugger+0x4:        ret
	2020-08-02T18:17:13.000Z

>How-To-Repeat:

>Fix: