Re: Xen 4.14.0 fails on Dell IoT Gateway without efi=no-rs

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 21/08/2020 07:50, Jan Beulich wrote:
> On 20.08.2020 21:12, Roman Shaposhnik wrote:
>> On Thu, Aug 20, 2020 at 5:56 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 
>> wrote:
>>> On 19/08/2020 23:50, Roman Shaposhnik wrote:
>>>>  Hi!
>>>>
>>>> below you can see a trace of Xen 4.14.0 failing on Dell IoT Gateway 3001
>>>> without efi=no-rs. Please let me know if I can provide any additional
>>>> information.
>>> Just to be able to get all datapoints, could you build Xen with
>>> CONFIG_EFI_SET_VIRTUAL_ADDRESS_MAP and see if the failure mode changes?
>> It does.
> As said on the other sub-thread - it doesn't:
>
>> (XEN)  00000ff900000-00000ffffffff type=11 attr=8000000000000000
>> (XEN) Unknown cachability for MFNs 0xff900-0xfffff
>> [...]
>> (XEN) ----[ Xen-4.14.0  x86_64  debug=y   Not tainted ]----
>> (XEN) CPU:    0
>> (XEN) RIP:    e008:[<00000000775e0d21>] 00000000775e0d21
>> (XEN) RFLAGS: 0000000000010046   CONTEXT: hypervisor
>> (XEN) rax: 0000000088411fe8   rbx: ffff82d0408afb28   rcx: ffff82d0408afa40
>> (XEN) rdx: 00000000ff900000   rsi: 00000000ff900000   rdi: 00000000775e4d58
>> (XEN) rbp: ffff82d0408afc00   rsp: ffff82d0408afa18   r8:  ffff82d0408afb28
>> (XEN) r9:  0000000000000000   r10: 00000000ff920000   r11: 0000000000020000
>> (XEN) r12: ffff82d0408afc40   r13: 0000000000000040   r14: 00000000775ce2c0
>> (XEN) r15: 00000000775cf9e8   cr0: 0000000080050033   cr4: 00000000001006e0
>> (XEN) cr3: 0000000070ddd000   cr2: 00000000ff900020
>> (XEN) fsb: 0000000000000000   gsb: 0000000000000000   gss: 0000000000000000
>> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 0000   cs: e008
>> (XEN) Xen code around <00000000775e0d21> (00000000775e0d21):
>> (XEN)  8b 11 45 33 c9 49 8b d8 <4c> 39 5a 20 75 0b 0f b7 42 30 48 8d 4c 10 
>> 17 eb
>> (XEN) Xen stack trace from rsp=ffff82d0408afa18:
>> (XEN)    00000000775ddb8e 00000000775e4d58 0000000000072812 0000000000000001
>> (XEN)    ffff82d0408afaf8 00000000ff900000 0000000000020000 00000000ff91fff0
>> (XEN)    00000000ff90cecc 00000000ff900060 0000000007f70021 0000000000000000
>> (XEN)    0000000077739001 ffff82d0409cc3c0 0000000000000020 ffff82d0409cc3c0
>> (XEN)    0000000000000020 ffff82d040646ce0 ffff82d040620d20 ffff82d0408afc40
>> (XEN)    00000000775e2e73 00000000775da608 ffff82d0408afc50 0000000000000000
>> (XEN)    0000000000000000 ffff82d0409b8950 00000000775e2ead ffff82d0409b8950
>> (XEN)    ffff82d0408afb48 8000000000000003 0000000000000000 0000000000000000
>> (XEN)    00000000775ddd88 00000000775da610 000000000000000a ffff82d0408afc50
>> (XEN)    000000000000000a ffff82d0408afc40 ffff82d040620d20 ffff82d040721200
>> (XEN)    ffff82d0408afb78 ffff82d0409eed20 ffff82d0408afbb8 0000000000000430
>> (XEN)    0000000000000002 ffff82d0408aff00 000000000000020c ffff82d0408afc50
>> (XEN)    00000000775de841 00000000775cf9e8 00000000775d03b5 00000000775ce2c0
>> (XEN)    0000000000000000 ffff82d0408afc40 0000000000000082 0000000000000000
>> (XEN)    00000000775d0798 ffff82d0408afc90 0000000000000000 0000000000002022
>> (XEN)    ffff82d04025e164 ffff82d0408afc40 0000000000000282 0000000000000000
>> (XEN)    ffff82d0408affff 0000000000000282 ffff82d040665fb6 00000000001006e0
>> (XEN)    ffff82d040202033 0000000000000002 ffff830077586e18 0000000000000003
>> (XEN)    ffff82d0408afcd0 0000000071233000 00007d2fbf750367 ffff82d0404ef931
>> (XEN)    0000000031746960 0000000000001d4b 0000000000000200 00333114010107dc
>> (XEN) Xen call trace:
>> (XEN)    [<00000000775e0d21>] R 00000000775e0d21
>> (XEN)    [<00000000775ddb8e>] S 00000000775ddb8e
>> (XEN)    [<0000000000000282>] F 0000000000000282
>> (XEN)    [<ffff830077586e18>] F ffff830077586e18
>> (XEN)
>> (XEN) Pagetable walk from 00000000ff900020:
> Hitting the very same address range, just the call trace has changed.

This mangled stack trace is a known problem with debug builds in Xen.

It should revert back to a more normal stack trace if you disable
CONFIG_FRAME_POINTER (which defaults to CONFIG_DEBUG).

~Andrew