Re: [Xen-devel] Regression in guest destruction caused by altp2m

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 27/07/2015 19:09, Wei Liu wrote:
> On Mon, Jul 27, 2015 at 04:18:15PM +0100, Wei Liu wrote:
>> Found this when I did "xl destroy" to a hvm guest *without* altp2m turned
>> on.
>>
>> Current staging branch.
>>
>> (XEN) ----[ Xen-4.6-unstable  x86_64  debug=y  Tainted:    C ]----
>> (XEN) CPU:    0
>> (XEN) RIP:    e008:[<ffff82d0801fce0d>] vmx_vmenter_helper+0x263/0x2f3
>> (XEN) RFLAGS: 0000000000010242   CONTEXT: hypervisor (d0v0)
>> (XEN) rax: 000000000000201a   rbx: ffff8300cf5f9000   rcx: 0000000000000000
>> (XEN) rdx: 0000000000000200   rsi: ffff830225fc5000   rdi: ffff8300cf5f9000
>> (XEN) rbp: ffff8300cf30fde8   rsp: ffff8300cf30fdd8   r8:  ffff8300cf0fc5e0
>> (XEN) r9:  00000016e7ea5ca3   r10: 0000000000000000   r11: 00000016f1000b66
>> (XEN) r12: ffff830227b18740   r13: ffff830227bda250   r14: ffff830227bda240
>> (XEN) r15: 0000000000000000   cr0: 0000000080050033   cr4: 00000000000026e0
>> (XEN) cr3: 000000000f03a000   cr2: 00007fb13dc65150
>> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 0000   cs: e008
>> (XEN) Xen stack trace from rsp=ffff8300cf30fdd8:
>> (XEN)    ffff8300cf5f9000 ffff8300cf5f9000 ffff8300cf30fdf8 ffff82d0801d95fb
>> (XEN)    ffff8300cf30fe18 ffff82d0802145eb ffff82d08012d455 ffff830227bda250
>> (XEN)    ffff8300cf30fe48 ffff82d0801d3e0c ffff8300cf5f9000 0000000000000001
>> (XEN)    ffff830227bdaf28 ffff830227bda000 ffff8300cf30fe68 ffff82d080174c6f
>> (XEN)    ffff8300cf5f9000 ffff8300cf5f9000 ffff8300cf30fe98 ffff82d080105e07
>> (XEN)    ffff82d0803545c0 0000000000000000 0000000000000000 ffff8300cf308000
>> (XEN)    ffff8300cf30fec8 ffff82d08012148a ffff82d080328080 ffff82d080328080
>> (XEN)    ffff82d080328080 ffffffffffffffff ffff8300cf30fef8 ffff82d08012cbe7
>> (XEN)    ffff8300ce68e000 00007fb13dc65150 ffffea00000715a0 0000000000000000
>> (XEN)    ffff8300cf30ff08 ffff82d08012cc3f 00007cff30cf00c7 ffff82d08024dd51
>> (XEN)    0000000000000000 0000000000000000 ffffea00000715a0 00007fb13dc65150
>> (XEN)    ffff8800cd4ff3d8 ffffea0000267a50 ffff880000000328 00000000000000a9
>> (XEN)    ffffea00000715a0 ffff8800cd4ff3d8 ffff880207c997b9 0000000000267a50
>> (XEN)    00007fb13dc65150 ffff8800cd4ff3d8 ffffea0000267a50 000000fa00000000
>> (XEN)    ffffffff8113d09d 000000000000e033 0000000000000202 ffff88000b807d68
>> (XEN)    000000000000e02b 000000000000beef 000000000000beef 000000000000beef
>> (XEN)    000000000000beef 0000000000000000 ffff8300ce68e000 0000000000000000
>> (XEN)    0000000000000000
>> (XEN) Xen call trace:
>> (XEN)    [<ffff82d0801fce0d>] vmx_vmenter_helper+0x263/0x2f3
>> (XEN)    [<ffff82d0801d95fb>] altp2m_vcpu_update_p2m+0x12/0x15
>> (XEN)    [<ffff82d0802145eb>] altp2m_vcpu_destroy+0x6b/0x94
>> (XEN)    [<ffff82d0801d3e0c>] hvm_vcpu_destroy+0x5a/0xa7
>> (XEN)    [<ffff82d080174c6f>] vcpu_destroy+0x5d/0x72
>> (XEN)    [<ffff82d080105e07>] complete_domain_destroy+0x49/0x186
>> (XEN)    [<ffff82d08012148a>] rcu_process_callbacks+0x144/0x1a5
>> (XEN)    [<ffff82d08012cbe7>] __do_softirq+0x82/0x8d
>> (XEN)    [<ffff82d08012cc3f>] do_softirq+0x13/0x15
>> (XEN)    [<ffff82d08024dd51>] process_softirqs+0x21/0x30
>> (XEN) 
>> (XEN) 
>> (XEN) ****************************************
>> (XEN) Panic on CPU 0:
>> (XEN) FATAL TRAP: vector = 6 (invalid opcode)
>> (XEN) ****************************************
>> (XEN) 
> This makes me think it doesn't matter if I do "xl destroy" or just
> normal shutdown. And another test to normally shutdown guest confirmed
> that.
>
> The machine I have is quite old and doesn't support EPT. The real issues
> seems to be that you failed to properly disable that feature for old
> machines.

The altp2m feature is designed (and implemented) to be emulated on
systems lacking hardware capabilities.

As such, teardown is necessary even on older systems, but I would agree
that there appears to be a bug.

~Andrew

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