Re: [Xen-devel] Linux 4.8-rc8 with Xen for-linus-4.9 branch: dom0 crashes on boot

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/10/2016 12:46, Sander Eikelenboom wrote:
> Hi All,
>
> Since the new merge window is emerging I took the liberty of testing a
> linux 4.8-rc8 tree with
> the Xen for-linus-4.9 branch pulled on top.
> Unfortunately this crashes dom0 early in boot under Xen.
> On bare-metal the same kernel boots fine.
> Under Xen a linux 4.8-rc8 kernel without the Xen branch pulled on top,
> also boots fine.

So this looks to be a regression in the Xen for-linux-4.9 branch.

>
> Hypervisor is a recentish xen-unstable build.
>
> The serial log is below.
> <snip>
> (XEN) [2016-10-02 11:31:53.106] Scrubbing Free RAM on 1 nodes using 6
> CPUs
> (XEN) [2016-10-02 11:31:53.217] .............................done.
> (XEN) [2016-10-02 11:31:56.242] Initial low memory virq threshold set
> at 0x4000 pages.
> (XEN) [2016-10-02 11:31:56.260] Std. Loglevel: All
> (XEN) [2016-10-02 11:31:56.277] Guest Loglevel: All
> (XEN) [2016-10-02 11:31:56.295] Xen is relinquishing VGA console.
> (XEN) [2016-10-02 11:31:56.396] *** Serial input -> DOM0 (type
> 'CTRL-a' three times to switch input to Xen)
> (XEN) [2016-10-02 11:31:56.396] Freed 308kB init memory
> (XEN) [2016-10-02 11:31:56.397] d0v0: unhandled page fault (ec=0000)
> (XEN) [2016-10-02 11:31:56.397] Pagetable walk from 0000000000000001:
> (XEN) [2016-10-02 11:31:56.397]  L4[0x000] = 0000000000000000
> ffffffffffffffff
> (XEN) [2016-10-02 11:31:56.397] domain_crash_sync called from entry.S:
> fault at ffff82d080244960 entry.o#create_bounce_frame+0x145/0x154
> (XEN) [2016-10-02 11:31:56.397] Domain 0 (vcpu#0) crashed on cpu#0:
> (XEN) [2016-10-02 11:31:56.397] ----[ Xen-4.8-unstable  x86_64 
> debug=y   Not tainted ]----
> (XEN) [2016-10-02 11:31:56.397] CPU:    0
> (XEN) [2016-10-02 11:31:56.397] RIP:    e033:[<ffffffff8101fdb9>]
> (XEN) [2016-10-02 11:31:56.397] RFLAGS: 0000000000000286   EM: 1  
> CONTEXT: pv guest (d0v0)
> (XEN) [2016-10-02 11:31:56.397] rax: 0000000000000000   rbx:
> ffffffff82248bb0   rcx: ffffffff8101bc10
> (XEN) [2016-10-02 11:31:56.397] rdx: 0000000000000001   rsi:
> ffffffff81f0aa50   rdi: ffffffff82248bb0
> (XEN) [2016-10-02 11:31:56.397] rbp: ffffffff82203e50   rsp:
> ffffffff82203dc0   r8:  ffffffff8101b550
> (XEN) [2016-10-02 11:31:56.397] r9:  0000000000000000   r10:
> 0000000000000000   r11: 0000000080802001
> (XEN) [2016-10-02 11:31:56.397] r12: 0000000000000000   r13:
> 0000000000000000   r14: ffffffff82215580
> (XEN) [2016-10-02 11:31:56.397] r15: 0000000000000000   cr0:
> 000000008005003b   cr4: 00000000000006e0
> (XEN) [2016-10-02 11:31:56.397] cr3: 000000054a601000   cr2:
> 0000000000000001
> (XEN) [2016-10-02 11:31:56.397] ds: 0000   es: 0000   fs: 0000   gs:
> 0000   ss: e02b   cs: e033
> (XEN) [2016-10-02 11:31:56.397] Guest stack trace from
> rsp=ffffffff82203dc0:
> (XEN) [2016-10-02 11:31:56.397]    ffffffff8101bc10 0000000080802001
> 0000000000000000 ffffffff8101fdb9
> (XEN) [2016-10-02 11:31:56.397]    000000010000e030 0000000000010086
> ffffffff82203e00 000000000000e02b
> (XEN) [2016-10-02 11:31:56.397]    ffffffff82203e50 ffffffff8101fcb5
> 0000000080802001 0000000000000000
> (XEN) [2016-10-02 11:31:56.397]    0000000000000000 ffffffff8101b550
> ffffffff82248bb0 ffffffff81f0aa50
> (XEN) [2016-10-02 11:31:56.397]    0000000000000001 ffffffff8101bc10
> ffffffff82203eb8 ffffffff81b7e9f4
> (XEN) [2016-10-02 11:31:56.397]    0000000000000000 ffffffff82203ea8
> 0000000080802001 0000000000000004
> (XEN) [2016-10-02 11:31:56.397]    ffffffff8101baa2 ffffffff82203f40
> ffffffff82248bb0 0000000000000000
> (XEN) [2016-10-02 11:31:56.397]    0000000000000000 ffffffff8101bc10
> 0000000000000000 ffffffff82203ed0
> (XEN) [2016-10-02 11:31:56.397]    ffffffff81b7ed45 0000000000000013
> ffffffff82203ee0 ffffffff810cc127
> (XEN) [2016-10-02 11:31:56.397]    ffffffff82203f28 ffffffff810ccdab
> ffffffff81f0aa50 ffffffff8101b550
> (XEN) [2016-10-02 11:31:56.397]    ffffffff82203f60 ffffffff82203f5c
> 0000000000000000 0000000000000000
> (XEN) [2016-10-02 11:31:56.397]    0000000000000000 ffffffff82203f40
> ffffffff810c83be ffffffff82600000
> (XEN) [2016-10-02 11:31:56.397]    ffffffff82203ff8 ffffffff8232946a
> 00100fa000000000 8080200100060800
> (XEN) [2016-10-02 11:31:56.397]    000000001789c3f5 0000000000000000
> 0000000000000000 0000000000000000
> (XEN) [2016-10-02 11:31:56.397]    0000000000000000 0000000000000000
> 0000000000000000 0000000000000000
> (XEN) [2016-10-02 11:31:56.397]    0000000000000000 0000000000000000
> 0000000000000000 0000000000000000
> (XEN) [2016-10-02 11:31:56.397]    0000000000000000 0000000000000000
> 0000000000000000 0000000000000000
> (XEN) [2016-10-02 11:31:56.397]    0000000000000000 0000000000000000
> 0000000000000000 0000000000000000
> (XEN) [2016-10-02 11:31:56.397]    0f00000060c0c748 ccccccccccccc305
> cccccccccccccccc cccccccccccccccc
> (XEN) [2016-10-02 11:31:56.397]    cccccccccccccccc cccccccccccccccc
> cccccccccccccccc cccccccccccccccc
> (XEN) [2016-10-02 11:31:56.397] Hardware Dom0 crashed: rebooting
> machine in 5 seconds.

Something in Linux at ffffffff8101fdb9 followed a NULL pointer.  Can you
see what it was with the linux debug symbols?

~Andrew

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