Xen 32-bit PV regression

Xen 32-bit PV regression

[Boris Ostrovsky]

Steven,

Looks like commit 198d208df (x86: Keep thread_info on thread stack in 
x86_32) broke Xen's 32-bit PV guests.

I poked a little at it and it seems that at least the ifdef in 
xen_cpu_up() needs to be adjusted to set up kernel_stack --- that allows 
CPUs to get going. This is not enough though (not particularly 
surprisingly) and we die a little later with #GPF in xen_iret.

-boris

Re: Xen 32-bit PV regression

[Boris Ostrovsky]

On 04/03/2014 11:23 PM, Boris Ostrovsky wrote:
> Steven,
>
> Looks like commit 198d208df (x86: Keep thread_info on thread stack in 
> x86_32) broke Xen's 32-bit PV guests.
>
> I poked a little at it and it seems that at least the ifdef in 
> xen_cpu_up() needs to be adjusted to set up kernel_stack --- that 
> allows CPUs to get going. This is not enough though (not particularly 
> surprisingly) and we die a little later with #GPF in xen_iret.


I should have probably included some output.


...
[    1.277533] Freeing unused kernel memory: 780K (c18fe000 - c19c1000)
[    1.280041] Write protecting the kernel text: 6120k
[    1.281477] Write protecting the kernel read-only data: 2472k
[    1.282177] NX-protecting the kernel data: 4120k
[    1.304957] general protection fault: 0000 [#1] SMP
[    1.305866] Modules linked in:
[    1.305866] CPU: 0 PID: 1 Comm: init Not tainted 3.14.0-32b #29
[    1.305866] task: eb880000 ti: eb84c000 task.ti: eb84c000
[    1.305866] EIP: e019:[<c100901f>] EFLAGS: 00010046 CPU: 0
[    1.305866] EIP is at xen_iret+0xb/0x29
[    1.305866] EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000000
[    1.305866] ESI: 00000000 EDI: 00000000 EBP: 00000000 ESP: eb84dfe0
[    1.305866]  DS: 007b ES: 007b FS: 0000 GS: 0000 SS: e021
[    1.305866] CR0: 8005003b CR2: bf8e0fe0 CR3: 2ac52000 CR4: 00040660
[    1.305866] Stack:
[    1.305866]  00000000 b760d020 00000073 00000200 bf8e0fe0 0000007b 
c2c2c2c2 c2c2c2c2
[    1.305866] Call Trace:
[    1.305866] Code: a1 d8 9f 9b c1 2d ec 1f 00 00 36 8b 40 10 36 8b 04 
85 e0 74 8f c1 36 8b 80 c0 90 9b c1 eb 2a 90 f7 44 24 08 00 00 02 80 75 
3d 50 <64> a1 d8 9f 9b c1 2d ec 1f 00 00 36 8b 40 10 36 8b 04 85 e0 74
[    1.305866] EIP: [<c100901f>] xen_iret+0xb/0x29 SS:ESP e021:eb84dfe0
[    1.305866] ---[ end trace e4f42ac1798ac467 ]---
[    1.369739] Kernel panic - not syncing: Attempted to kill init! 
exitcode=0x0000000b