GPF while testing fwts msr

[Alex Hung]

On 01/29/2012 05:59 AM, Chris Van Hoof wrote:
> Hey guys,
> While testing the latest fwts-live image[0] (3.2.0-11.19) in a kvm
> instance I noticed that when the msr test is executed I'm seeing a GPF:
>
> [   19.495910] general protection fault: 0000 [#1] SMP
> [   19.496033] CPU 0
> [   19.496068] Modules linked in: msr ppdev parport_pc parport mac_hid
> psmouse serio_raw i2c_piix4 squashfs overlayfs nls_iso8859_1 nls_cp437
> vfat fat floppy 8139too 8139cp zram(C)
> [   19.496461]
> [   19.496490] Pid: 2052, comm: fwts Tainted: G         C
> 3.2.0-11-generic #19-Ubuntu Bochs Bochs
> [   19.496640] RIP: 0010:[<ffffffff8103bf5d>]  [<ffffffff8103bf5d>]
> native_read_msr_safe+0xd/0x30
> [   19.496990] RSP: 0018:ffff88001ba73db0  EFLAGS: 00000086
> [   19.497170] RAX: 0000000012a40000 RBX: ffff88001ba73e58 RCX:
> 0000000000000480
> [   19.497376] RDX: 00000000ffff8800 RSI: ffff88001ba73dcc RDI:
> 0000000000000480
> [   19.497576] RBP: ffff88001ba73db0 R08: 0000000000000000 R09:
> 0000000000000000
> [   19.497576] R10: 0000000000000480 R11: 0000000000000246 R12:
> ffffffff81326400
> [   19.497576] R13: 0000000000000000 R14: ffffffff81cdc000 R15:
> 0000000000000008
> [   19.497576] FS:  00007f43dabb6720(0000) GS:ffff88001f400000(0000)
> knlGS:0000000000000000
> [   19.497576] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   19.497576] CR2: 00007f43dabbc000 CR3: 000000001bc9a000 CR4:
> 00000000000006f0
> [   19.497576] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000
> [   19.497576] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
> 0000000000000400
> [   19.497576] Process fwts (pid: 2052, threadinfo ffff88001ba72000,
> task ffff88001da00000)
> [   19.497576] Stack:
> [   19.497576]  ffff88001ba73dd8 ffffffff8132641c ffffffff81187063
> ffff88001b9da600
> [   19.497576]  0000000000000246 ffff88001ba73e48 ffffffff810a0ec7
> 0000000000000000
> [   19.497576]  0000000000000000 ffff88001d87d950 0000000000000000
> 0000000000000000
> [   19.497576] Call Trace:
> [   19.497576]  [<ffffffff8132641c>] __rdmsr_safe_on_cpu+0x1c/0x40
> [   19.497576]  [<ffffffff81187063>] ? user_path_at_empty+0x63/0xa0
> [   19.497576]  [<ffffffff810a0ec7>] smp_call_function_single+0x147/0x160
> [   19.497576]  [<ffffffff813265ce>] rdmsr_safe_on_cpu+0x4e/0x70
> [   19.497576]  [<ffffffffa00900d8>] msr_read+0x98/0xd0 [msr]
> [   19.497576]  [<ffffffff8129b723>] ? security_file_permission+0x93/0xb0
> [   19.497576]  [<ffffffff81177650>] vfs_read+0xb0/0x180
> [   19.497576]  [<ffffffff811778e2>] sys_pread64+0xa2/0xb0
> [   19.497576]  [<ffffffff8165e2c2>] system_call_fastpath+0x16/0x1b
> [   19.497576] Code: 89 e5 66 66 66 66 90 0f 01 f9 48 89 c6 48 89 d0 89
> 0f 48 c1 e0 20 48 09 f0 5d c3 0f 1f 00 55 48 89 e5 66 66 66 66 90 89 f9
> 0f 32<45>  31 c0 89 c7 48 89 d0 44 89 06 48 c1 e0 20 89 f9 48 09 c8 5d
> [   19.497576] RIP  [<ffffffff8103bf5d>] native_read_msr_safe+0xd/0x30
> [   19.497576]  RSP<ffff88001ba73db0>
> [   19.497576] ---[ end trace abd45dfe942fc0ed ]---
>
> ... this was of course while running with the fwts-live frontend, but
> can also be easily reproduced with `sudo fwts msr`.
>
> On the host machine (Precise based) I noticed this is generated when I
> hit the GPF:
>
> [592075.713605] kvm: 25101: cpu0 unhandled rdmsr: 0x1fa
> [592075.714107] kvm: 25101: cpu0 unhandled rdmsr: 0x3f1
> [592080.880260] kvm_get_msr_common: 10 callbacks suppressed
>
> I then tried to reproduce this on real hardware and cannot reproduce the
> failure which got me looking at:
>
> https://lkml.org/lkml/2012/1/6/173
>
> ... although I'm not sure if it's relevant here.
>
> Also to note, I'm running fwts version 0.24.16.
>
> Cheers,
> Chris
>
> [0] --
> http://hwe.ubuntu.com/fwts-live/images/fwts-live-oneiric-amd64-usb-hdd-20120127-0.img.bz2
>
>
>
>
>
>
Not all MSR registers are supported in all CPUs and some read/write of 
MSR may depend on others. Read/Write to unsupported MSR will generate GPF.

1FAH (IA32_DCA_0_CAP) DCA type 0 Status and Control register
3F1H  (MSR_PEBS_ENABLE PEBS) Control (R/W)

It could be KVM does not support the MSR registers. Many CPUs support 
these MSR and the error will not be duplicated with real hardware.

Cheers,
Alex Hung