[Xen-devel] blktap2 and CONFIG_XEN_BLKBACK_PAGEMAP

[Kaushik Kumar Ram <kaushik@xxxxxxxx>]

Is it necessary to use blkback_pagemap with blktap2? Since the use of 
blkback_pagemap is configurable I tried without it and my system crashed (crash 
dump attached below). Or is it a bug?

I am using about a month old xen-unstable.hg with linux-2.6.18-xen.hg (both 64 
bit). 

Thanks.
-Kaushik

(XEN) mm.c:889:d0 Error getting mfn 80765 (pfn 3fba6) from L1 entry 
8000000080765027 for l1e_owner=0, pg_owner=0
(XEN) mm.c:5046:d0 ptwr_emulate: could not get_page_from_l1e()
Unable to handle kernel paging request at ffff8800388f6688 RIP: 
 [<ffffffff803dc7d6>] blktap_map_uaddr_fn+0xa6/0xc0
PGD 1140067 PUD 1141067 PMD 1306067 PTE 80100000388f6065
Oops: 0003 [1] SMP 
CPU 0 
Modules linked in: e1000e sd_mod ata_piix libata thermal fan
Pid: 4183, comm: blkback.1.sda1 Not tainted 2.6.18.8-xen0 #40
RIP: e030:[<ffffffff803dc7d6>]  [<ffffffff803dc7d6>] 
blktap_map_uaddr_fn+0xa6/0xc0
RSP: e02b:ffff880039d01840  EFLAGS: 00010297
RAX: 8000000080765027 RBX: ffff8800388f6688 RCX: ffff880039d01908
RDX: 00002b218a8d1000 RSI: ffff880001fb15d0 RDI: ffff8800388f6688
RBP: ffff880039d01850 R08: 00000000000388f6 R09: 0000000000000000
R10: 0000000000000000 R11: 00000000000002c8 R12: ffff8800388f6688
R13: 00002b218a8d1000 R14: 00002b218a8d2000 R15: ffff88003890e2a0
FS:  00002af9674c06e0(0000) GS:ffffffff8058c000(0000) knlGS:0000000000000000
CS:  e033 DS: 0000 ES: 0000
Process blkback.1.sda1 (pid: 4183, threadinfo ffff880039d00000, task 
ffff88003e8cf080)
Stack:  ffff8800388f6688 ffff880001fb15d0 ffff880039d018f0 ffffffff80270033
 0000001a00000039 ffff880039d01908 ffffffff803dc730 ffff88003a714080
 ffff8800389802b0 00002b218a8d2000 00002b218a8d2000 ffff88003c03b430
Call Trace:
 [<ffffffff80270033>] apply_to_page_range+0x4e3/0x590
 [<ffffffff803dc730>] blktap_map_uaddr_fn+0x0/0xc0
 [<ffffffff803dac01>] blktap_map_uaddr+0x21/0x30
 [<ffffffff803db70c>] blktap_device_do_request+0x67c/0xfe0
 [<ffffffff8023f36c>] __mod_timer+0xbc/0xe0
 [<ffffffff802088b0>] __switch_to+0x370/0x5b0
 [<ffffffff8023f1dc>] lock_timer_base+0x2c/0x60
 [<ffffffff8023f9c6>] del_timer+0x56/0x70
 [<ffffffff80344715>] __generic_unplug_device+0x25/0x30
 [<ffffffff803459d0>] generic_unplug_device+0x20/0x60
 [<ffffffff803d3196>] unplug_queue+0x26/0x50
 [<ffffffff803d3dea>] blkif_schedule+0x55a/0x690
 [<ffffffff803d3890>] blkif_schedule+0x0/0x690
 [<ffffffff8024b12a>] kthread+0xda/0x110
 [<ffffffff8020a428>] child_rip+0xa/0x12
 [<ffffffff8024b050>] kthread+0x0/0x110
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