[Devel] double faults in Virtuozzo KVM

[Denis Kirjanov]

Hi, we're seeing double faults in async_page_fault.
_Some_ of them related to the fact that during the faults RSP points
to userspace and it leads to double-fault scenario.

Is it known problem?

Thanks!

[11587.895394] Hardware name: Virtuozzo KVM, BIOS 1.9.1-5.3.2.vz7.6 04/01/2014
[11587.895394] task: ffff88020bee0000 ti: ffff880204b60000 task.ti:
ffff880204b60000
[11587.895394] RIP: 0010:[<ffffffff816a1bdd>]  [<ffffffff816a1bdd>]
async_page_fault+0xd/0x30
[11587.895394] RSP: 002b:ffff880234f61fd8  EFLAGS: 00010096
[11587.895394] RAX: 00000000816a192c RBX: 0000000000000001 RCX: ffffffff816a192c
[11587.895394] RDX: ffff88023fc03fc0 RSI: 0000000000000000 RDI: ffff880234f62098
[11587.895394] RBP: ffff880234f62088 R08: ffff88023fbfffc0 R09: ffff88003642af00
[11587.895394] R10: 0000000000008000 R11: 0000000000000000 R12: ffff88023fc04f58
[11587.895394] R13: 0000000000000028 R14: 0000000000000000 R15: 0000000000000000
[11587.895394] FS:  00007ff80ffc1880(0000) GS:ffff88023fc00000(0000)
knlGS:0000000000000000
[11587.895394] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[11587.895394] CR2: ffff880234f61fc8 CR3: 00000000b9436000 CR4: 00000000000007f0
[11587.895394] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[11587.895394] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[11587.895394] Stack:
[11587.895394]  0000c7e9e11c7f44 0000270f05836600 906666906666fb02
be00000001b9d231
[11587.895394]  e8df8948ffffffff 0000000231a6fba8 0001000000000008
0000000000000000
[11587.895394]  0002000000000000 0000000000000000 0003000000000000
0000000000000000
[11587.895394] Call Trace:
[11587.895394] Code: 48 89 e7 48 8b 74 24 78 48 c7 44 24 78 ff ff ff
ff e8 78 3d 00 00 e9 33 02 00 00 0f 1f 00 66 66 90 66 66 90 66 66 90
48 83 ec 78 <e8> 7e 01 00 00 48 89 e7 48 8b 74 24 78 48 c7 44 24 78 ff
ff ff
[11587.895394] RIP  [<ffffffff816a1bdd>] async_page_fault+0xd/0x30
[11587.895394]  RSP <ffff880234f61fd8>