Bisected: drivers/block/xen-blkback/xenbus.c:327 xen_blkif_disconnect+0x24f/0x260

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Hi Juergen,

I'm having trouble booting my DomU's when trying to use a linux-5.19 kernel for 
both Dom0 and DomU.
A dom0 5.19 kernel with a domU 5.18 kernel boots fine.
I'm using durect kernel boot to boot the domU guest (kernel=  and ramdisk= 
parameters).

Since both xen-blkback and xen-blkfront could be into play,
I bisected this by keeping dom0 fixed as a 5.19 kernel and do the bisecting on 
the domU kernel.

Bisecting leads to commit 4573240f0764ee79d7558d74fc535baa1e110d20 "xen/xenbus: 
eliminate xenbus_grant_ring()"
Reverting this specific commit makes the domU boot fine again.

I have added the splat from dom0 kernel below (from using 5.19.8 kernel for 
both dom0 and domU),
the domU does not seem to have any interessting logging,
apart from not being able to find the root filesystem.

Do you have any ideas ?

--
Sander




Dom0:

[144007.320877] xen_bridge: port 3(vif17.0) entered blocking state
[144007.320885] xen_bridge: port 3(vif17.0) entered disabled state
[144007.320993] device vif17.0 entered promiscuous mode
[144011.012144] xen-blkback: backend/vbd/17/51712: using 2 queues, protocol 1 
(x86_64-abi) persistent grants
[144011.014046] vbd vbd-17-51712: 9 mapping in shared page 9 from domain 17
[144011.015339] vbd vbd-17-51712: 2 mapping ring-ref port 13
[144011.016666] ------------[ cut here ]------------
[144011.016672] WARNING: CPU: 0 PID: 50 at 
drivers/block/xen-blkback/xenbus.c:327 xen_blkif_disconnect+0x24f/0x260
[144011.016687] Modules linked in:
[144011.016691] CPU: 0 PID: 50 Comm: xenwatch Not tainted 
5.19.8-20220913-doflr-mac80211debug+ #1
[144011.016695] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS V1.8B1 
09/13/2010
[144011.016698] RIP: e030:xen_blkif_disconnect+0x24f/0x260
[144011.016702] Code: 20 48 8d 56 20 48 8d 48 e0 48 3b 54 24 08 0f 84 a7 fe ff ff 4c 
8b 74 24 10 48 89 4c 24 10 eb 82 0f 0b 0f 0b 0f 0b 0f 0b 0f 0b <0f> 0b e9 ef fe 
ff ff b8 f0 ff ff ff e9 34 ff ff ff 41 54 55 48 89
[144011.016705] RSP: e02b:ffffc90000847dd8 EFLAGS: 00010202
[144011.016708] RAX: 0000000000000040 RBX: 0000000000000001 RCX: 
ffff88802a03bc60
[144011.016710] RDX: 0000000000000000 RSI: 0000000000000200 RDI: 
00000000ffffffff
[144011.016711] RBP: ffff88802a03bc00 R08: 0000000000000001 R09: 
ffffffff82296a93
[144011.016713] R10: 00000000fffffffc R11: 00000000000222cd R12: 
0000000000000000
[144011.016715] R13: ffff8880187d5000 R14: ffff88802a03bc40 R15: 
ffff88801caf0c00
[144011.016730] FS:  0000000000000000(0000) GS:ffff88807d200000(0000) 
knlGS:0000000000000000
[144011.016732] CS:  e030 DS: 0000 ES: 0000 CR0: 0000000080050033
[144011.016740] CR2: 00007ffe03596084 CR3: 000000000adee000 CR4: 
0000000000000660
[144011.016744] Call Trace:
[144011.016744]  <TASK>
[144011.016747]  frontend_changed+0x3b2/0x470
[144011.016752]  xenwatch_thread+0x9c/0x170
[144011.016757]  ? cpu_core_flags+0x10/0x10
[144011.016764]  ? find_watch+0x50/0x50
[144011.016766]  kthread+0xe3/0x110
[144011.016773]  ? kthread_complete_and_exit+0x20/0x20
[144011.016782]  ret_from_fork+0x22/0x30
[144011.016785]  </TASK>
[144011.016786] ---[ end trace 0000000000000000 ]---
[144011.016796] ------------[ cut here ]------------
[144011.016797] WARNING: CPU: 0 PID: 50 at 
drivers/block/xen-blkback/xenbus.c:327 xen_blkif_disconnect+0x24f/0x260
[144011.016801] Modules linked in:
[144011.016802] CPU: 0 PID: 50 Comm: xenwatch Tainted: G        W         
5.19.8-20220913-doflr-mac80211debug+ #1
[144011.016805] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS V1.8B1 
09/13/2010
[144011.016806] RIP: e030:xen_blkif_disconnect+0x24f/0x260
[144011.016808] Code: 20 48 8d 56 20 48 8d 48 e0 48 3b 54 24 08 0f 84 a7 fe ff ff 4c 
8b 74 24 10 48 89 4c 24 10 eb 82 0f 0b 0f 0b 0f 0b 0f 0b 0f 0b <0f> 0b e9 ef fe 
ff ff b8 f0 ff ff ff e9 34 ff ff ff 41 54 55 48 89
[144011.016811] RSP: e02b:ffffc90000847dd8 EFLAGS: 00010202
[144011.016813] RAX: 0000000000000040 RBX: 0000000000000001 RCX: 
ffff88802a03bdd8
[144011.016815] RDX: 0000000000000000 RSI: 0000000000000200 RDI: 
00000000ffffffff
[144011.016816] RBP: ffff88802a03bd78 R08: 0000000000000001 R09: 
ffffffff82296a93
[144011.016818] R10: 00000000fffffffc R11: 00000000000222cd R12: 
0000000000000001
[144011.016819] R13: ffff8880187d5000 R14: ffff88802a03bdb8 R15: 
ffff88801caf0c00
[144011.016824] FS:  0000000000000000(0000) GS:ffff88807d200000(0000) 
knlGS:0000000000000000
[144011.016825] CS:  e030 DS: 0000 ES: 0000 CR0: 0000000080050033
[144011.016827] CR2: 00007ffe03596084 CR3: 000000000adee000 CR4: 
0000000000000660
[144011.016829] Call Trace:
[144011.016831]  <TASK>
[144011.016832]  frontend_changed+0x3b2/0x470
[144011.016835]  xenwatch_thread+0x9c/0x170
[144011.016837]  ? cpu_core_flags+0x10/0x10
[144011.016840]  ? find_watch+0x50/0x50
[144011.016842]  kthread+0xe3/0x110
[144011.016844]  ? kthread_complete_and_exit+0x20/0x20
[144011.016848]  ret_from_fork+0x22/0x30
[144011.016851]  </TASK>
[144011.016852] ---[ end trace 0000000000000000 ]---
[144011.154673] vif vif-17-0 vif17.0: Guest Rx ready
[144011.154711] xen_bridge: port 3(vif17.0) entered blocking state
[144011.154713] xen_bridge: port 3(vif17.0) entered forwarding state