Re: [Xen-devel] [PATCHv9 0/9] Xen: extend kexec hypercall for use with pv-ops kernels

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 18/10/2013 19:40, Daniel Kiper wrote:
> On Tue, Oct 08, 2013 at 05:55:01PM +0100, David Vrabel wrote:
>> The series (for Xen 4.4) improves the kexec hypercall by making Xen
>> responsible for loading and relocating the image.  This allows kexec
>> to be usable by pv-ops kernels and should allow kexec to be usable
>> from a HVM or PVH privileged domain.
> I could not load panic image because Xen crashes in following way:
>
> (XEN) ----[ Xen-4.4-unstable  x86_64  debug=y  Tainted:    C ]----
> (XEN) CPU:    3
> (XEN) RIP:    e008:[<ffff82d080114ef2>] kimage_free+0x67/0xd2
> (XEN) RFLAGS: 0000000000010286   CONTEXT: hypervisor
> (XEN) rax: ffff820040037000   rbx: f000ff53f000e2c3   rcx: 0000000000000037
> (XEN) rdx: ffff820040000000   rsi: 0000000000000040   rdi: ffff83007faea1d8
> (XEN) rbp: ffff83007fae7d48   rsp: ffff83007fae7d28   r8: fffffffffffffe31
> (XEN) r9:  0000000000000009   r10: 0000000000000282   r11: 0000000000bfd000
> (XEN) r12: ffff820040037000   r13: f000ff53f000e2c3   r14: ffff830076b1df20
> (XEN) r15: 0000000013bfd000   cr0: 0000000080050033   cr4: 00000000000026f0
> (XEN) cr3: 0000000076389000   cr2: ffff820040037000
> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: e010   cs: e008
> (XEN) Xen stack trace from rsp=ffff83007fae7d28:
> (XEN)    ffff830076b1df20 00000000ffffff9d ffff830076b1de50 0000000000000001
> (XEN)    ffff83007fae7d98 ffff82d0801151f9 0000000000000010 ffff83007fae7de0
> (XEN)    00000000000000c0 ffff83007fae7de0 000000000000003e 0000000013f4f720
> (XEN)    ffff880039c56b50 0000000000000000 ffff83007fae7dc8 ffff82d0801152fe
> (XEN)    ffff83007fae7dc8 00000000fffffff2 ffff830076b1de50 00007fff4a4391f0
> (XEN)    ffff83007fae7ee8 ffff82d0801144c0 ffff83007fae7ef8 0000000000000000
> (XEN)    ffff83007fae7e48 ffff82d08011d7d2 ffff83007fae7e18 ffff82d080270d20
> (XEN)    ffff83007fad9060 0000000000075a0c 0000000000000000 ffff83007fad9000
> (XEN)    ffff820040035000 00007ff000000003 00000006003e0001 00007fbf8d9b0004
> (XEN)    0000000013f4f720 ffff83007faea000 ffff83007fae7e68 ffff82d08016fa43
> (XEN)    ffff83007fae7e88 ffff82d080221348 ffff83007faea000 ffff83007fae7f18
> (XEN)    ffff83007fae7ef8 ffff82d0802214a8 000000000af2f749 0000000000000000
> (XEN)    0000000000000217 00007fbf8cfd5577 0000000000000100 00007fbf8cfd5577
> (XEN)    ffff83007fae7ed8 ffff82d08016fa43 ffff83007fad9000 0000000000000003
> (XEN)    ffff83007fae7ef8 ffff82d0801145c9 00007cff805180c7 ffff82d0802268cb
> (XEN)    ffffffff810014aa 0000000000000025 0000000000000000 00007fff4a439270
> (XEN)    00000000000000a0 00007fbf8d9b1000 ffff88003951dea8 ffff880039912c00
> (XEN)    0000000000000286 000000000155d850 0000000000200000 0000000013f4f720
> (XEN)    0000000000000025 ffffffff810014aa 00007fbf8d8faa55 00007fbf8d9af004
> (XEN)    0000000000000004 0001010000000000 ffffffff810014aa 000000000000e033
> (XEN) Xen call trace:
> (XEN)    [<ffff82d080114ef2>] kimage_free+0x67/0xd2
> (XEN)    [<ffff82d0801151f9>] do_kimage_alloc+0x29c/0x2f0
> (XEN)    [<ffff82d0801152fe>] kimage_alloc+0xb1/0xe6
> (XEN)    [<ffff82d0801144c0>] do_kexec_op_internal+0x68e/0x789
> (XEN)    [<ffff82d0801145c9>] do_kexec_op+0xe/0x12
> (XEN)    [<ffff82d0802268cb>] syscall_enter+0xeb/0x145
> (XEN)
> (XEN) Pagetable walk from ffff820040037000:
> (XEN)  L4[0x104] = 000000007ffd0063 ffffffffffffffff
> (XEN)  L3[0x001] = 000000007ffce063 ffffffffffffffff
> (XEN)  L2[0x000] = 000000007ffc5063 ffffffffffffffff
> (XEN)  L1[0x037] = f000ff53f000e063 ffffffffffffffff
> (XEN)
> (XEN) ****************************************
> (XEN) Panic on CPU 3:
> (XEN) FATAL PAGE FAULT
> (XEN) [error_code=0009]
> (XEN) Faulting linear address: ffff820040037000
> (XEN) ****************************************
>
> Normal kernel could be loaded but when it is executed something
> crashes very early. Following message is displayed
>
> I'm in purgatory
> early console in decompress_kernel
>
> and machine is restarted shortly.
>
> I have done tests with latest kexec-tools and Xen versions.
>
> Daniel

David - this looks curiously like the double-free crash I fixed on v6 in
XenServer.  Did you remember to merge the patch into your series?

Daniel: Your tests show that the new load kernel is in control of the
machine.  The restart is therefore a bug in whichever kernel you used,
presumably making some false assumption about the state of the machine.

~Andrew


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