Comment 0 for bug 1853981

While building the test kernel for Disco, the kernel built from master-next branch (head: e903d6a UBUNTU: upstream stable to v4.19.83, v5.3.10) will result in the following error on boot with an AMD64 KVM node:
[ 2.724234] [TTM] Initializing pool allocator
[ 2.725770] [TTM] Initializing DMA pool allocator
[ 2.727918] [drm] fb mappable at 0xFC000000
[ 2.729462] [drm] vram aper at 0xFC000000
[ 2.729980] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
[ 2.730902] [drm] size 33554432
[ 2.735026] #PF error: [normal kernel read fault]
[ 2.735028] PGD 0 P4D 0
[ 2.735032] Oops: 0000 [#1] SMP PTI
[ 2.735036] CPU: 1 PID: 211 Comm: systemd-udevd Not tainted 5.0.0-37-generic #40
[ 2.736230] [drm] fb depth is 16
[ 2.738490] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[ 2.739526] [drm] pitch is 2048
[ 2.740751] RIP: 0010:attempt_merge+0x145/0x9d0
[ 2.740753] Code: 84 a2 02 00 00 41 8b 7c 24 24 4d 8b 44 24 30 c1 ef 09 89 f8 4c 01 c0 48 3b 43 30 0f 85 0e ff ff ff 48 8b 53 38 4d 8b 7c 24 40 <8b> 42 20 45 8b 5f 24 89 44 24 3c 4d 85 ff 74 20 41 8b 47 30 85 c0
[ 2.740754] RSP: 0018:ffffb4964067f2f8 EFLAGS: 00010246
[ 2.753490] input: VirtualPS/2 VMware VMMouse as /devices/platform/i8042/serio1/input/input4
[ 2.758417] RAX: 0000000000000000 RBX: ffff9a1b33261200 RCX: 0000000000000000
[ 2.758418] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[ 2.758418] RBP: ffffb4964067f378 R08: 0000000000000000 R09: 0000000000000004
[ 2.758419] R10: 0000000000000001 R11: 0000000000000800 R12: ffff9a1b33260000
[ 2.758420] R13: ffff9a1b330c7070 R14: ffff9a1b330c7070 R15: 0000000000000000
[ 2.758421] FS: 00007fd50d4748c0(0000) GS:ffff9a1b7db00000(0000) knlGS:0000000000000000
[ 2.758422] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2.758423] CR2: 0000000000000020 CR3: 000000003377e000 CR4: 00000000000006e0
[ 2.758426] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2.786182] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 2.786183] Call Trace:
[ 2.786188] ? insert_work+0x6c/0x80
[ 2.786193] ? __sbitmap_get_word+0x31/0x90
[ 2.786194] blk_attempt_req_merge+0xe/0x30
[ 2.786198] elv_attempt_insert_merge+0x35/0x90
[ 2.786201] blk_mq_sched_try_insert_merge+0x42/0x50
[ 2.786203] dd_insert_requests+0x90/0x1c0
[ 2.786206] blk_mq_sched_insert_request+0x12d/0x1a0
[ 2.786208] blk_mq_make_request+0x36c/0x4d0
[ 2.786210] generic_make_request+0x19e/0x400
[ 2.786212] submit_bio+0x49/0x140
[ 2.786215] ? guard_bio_eod+0x32/0x100
[ 2.786217] submit_bh_wbc+0x185/0x1b0
[ 2.786219] block_read_full_page+0x24d/0x330
[ 2.786222] ? check_disk_change+0x70/0x70
[ 2.786225] ? count_shadow_nodes+0x140/0x140
[ 2.786228] blkdev_readpage+0x18/0x20
[ 2.786232] do_read_cache_page+0x374/0x7a0
[ 2.786234] ? blkdev_writepages+0x10/0x10
[ 2.786237] ? get_page_from_freelist+0xefe/0x1440
[ 2.786240] ? __radix_tree_replace+0x59/0xf0
[ 2.786243] read_cache_page+0x12/0x20
[ 2.786244] read_dev_sector+0x2d/0xd0
[ 2.786246] read_lba+0xcd/0x220
[ 2.786248] efi_partition+0x1e4/0x6de
[ 2.786250] ? vsnprintf+0x103/0x520
[ 2.786252] ? snprintf+0x49/0x60
[ 2.786253] ? is_gpt_valid.part.7+0x470/0x470
[ 2.786255] check_partition+0x13e/0x238
[ 2.786256] rescan_partitions+0xaf/0x2a0
[ 2.786259] ? _cond_resched+0x19/0x30
[ 2.786260] __blkdev_get+0x393/0x550
[ 2.786262] blkdev_get+0x10c/0x330
[ 2.786264] ? wake_up_bit+0x42/0x50
[ 2.786267] ? unlock_new_inode+0x53/0x70
[ 2.786269] ? bdget+0x111/0x130
[ 2.786270] __device_add_disk+0x321/0x480
[ 2.786272] device_add_disk+0x13/0x20
[ 2.786275] virtblk_probe+0x4ef/0x79f [virtio_blk]
[ 2.786278] virtio_dev_probe+0x172/0x230
[ 2.786282] really_probe+0xfe/0x3b0
[ 2.786284] driver_probe_device+0xba/0x100
[ 2.786286] __driver_attach+0xf1/0x120
[ 2.786288] ? driver_probe_device+0x100/0x100
[ 2.786290] bus_for_each_dev+0x79/0xc0
[ 2.786292] ? kmem_cache_alloc_trace+0x1bd/0x1d0
[ 2.786294] driver_attach+0x1e/0x20
[ 2.786295] bus_add_driver+0x159/0x230
[ 2.786297] ? 0xffffffffc0410000
[ 2.786299] driver_register+0x70/0xc0
[ 2.786300] ? 0xffffffffc0410000
[ 2.786302] register_virtio_driver+0x20/0x30
[ 2.786304] init+0x56/0x1000 [virtio_blk]
[ 2.786308] do_one_initcall+0x4a/0x1c4
[ 2.786310] ? _cond_resched+0x19/0x30
[ 2.786311] ? kmem_cache_alloc_trace+0x167/0x1d0
[ 2.786314] do_init_module+0x60/0x220
[ 2.786316] load_module+0x1797/0x1a00
[ 2.786319] __do_sys_finit_module+0xbd/0x120
[ 2.786321] ? __do_sys_finit_module+0xbd/0x120
[ 2.786323] __x64_sys_finit_module+0x1a/0x20
[ 2.786325] do_syscall_64+0x5a/0x110
[ 2.786329] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 2.786330] RIP: 0033:0x7fd50d7012e9
[ 2.786332] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 77 cb 0c 00 f7 d8 64 89 01 48
[ 2.786332] RSP: 002b:00007fff6dd12248 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[ 2.786334] RAX: ffffffffffffffda RBX: 000055b98c946aa0 RCX: 00007fd50d7012e9
[ 2.786335] RDX: 0000000000000000 RSI: 00007fd50d5e2cad RDI: 0000000000000005
[ 2.786335] RBP: 00007fd50d5e2cad R08: 0000000000000000 R09: 000055b98c926ab0
[ 2.786336] R10: 0000000000000005 R11: 0000000000000246 R12: 0000000000000000
[ 2.786337] R13: 000055b98c934800 R14: 0000000000020000 R15: 000055b98c946aa0
[ 2.786338] Modules linked in: psmouse cirrus(+) ttm virtio_blk(+) drm_kms_helper virtio_net(+) syscopyarea sysfillrect net_failover sysimgblt failover fb_sys_fops drm floppy i2c_piix4 pata_acpi
[ 2.786345] CR2: 0000000000000020
[ 2.786379] ---[ end trace 1c7dd9ecceb0cff9 ]---
[ 2.786382] RIP: 0010:attempt_merge+0x145/0x9d0
[ 2.786383] Code: 84 a2 02 00 00 41 8b 7c 24 24 4d 8b 44 24 30 c1 ef 09 89 f8 4c 01 c0 48 3b 43 30 0f 85 0e ff ff ff 48 8b 53 38 4d 8b 7c 24 40 <8b> 42 20 45 8b 5f 24 89 44 24 3c 4d 85 ff 74 20 41 8b 47 30 85 c0
[ 2.786384] RSP: 0018:ffffb4964067f2f8 EFLAGS: 00010246
[ 2.786385] RAX: 0000000000000000 RBX: ffff9a1b33261200 RCX: 0000000000000000
[ 2.786386] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[ 2.786386] RBP: ffffb4964067f378 R08: 0000000000000000 R09: 0000000000000004
[ 2.786387] R10: 0000000000000001 R11: 0000000000000800 R12: ffff9a1b33260000
[ 2.786388] R13: ffff9a1b330c7070 R14: ffff9a1b330c7070 R15: 0000000000000000
[ 2.786389] FS: 00007fd50d4748c0(0000) GS:ffff9a1b7db00000(0000) knlGS:0000000000000000
[ 2.786390] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2.786391] CR2: 0000000000000020 CR3: 000000003377e000 CR4: 00000000000006e0
[ 2.786394] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2.786395] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 2.786728] input: VirtualPS/2 VMware VMMouse as /devices/platform/i8042/serio1/input/input3
[ 2.787939] fbcon: cirrusdrmfb (fb0) is primary device
[ 2.802935] Console: switching to colour frame buffer device 128x48
[ 2.969597] virtio_net virtio1 ens4: renamed from eth0
[ 3.078798] cirrus 0000:00:02.0: fb0: cirrusdrmfb frame buffer device