Re: Crash when using cpupools

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Juergen,

> On 6 Sep 2021, at 09:23, Juergen Gross <jgross@xxxxxxxx> wrote:
> 
> On 03.09.21 17:41, Bertrand Marquis wrote:
>> Hi,
>> While doing some investigation with cpupools I encountered a crash when 
>> trying to isolate a guest to its own physical cpu.
>> I am using current staging status.
>> I did the following (on FVP with 8 cores):
>> - start dom0 with dom0_max_vcpus=1
>> - remove core 1 from dom0 cpupool: xl cpupool-cpu-remove Pool-0 1
>> - create a new pool: xl cpupool-create name=\"NetPool\”
>> - add core 1 to the pool: xl cpupool-cpu-add NetPool 1
>> - create a guest in NetPool using the following in the guest config: 
>> pool=“NetPool"
>> I end with a crash with the following call trace during guest creation:
>> (XEN) Xen call trace:
>> (XEN)    [<0000000000234cb0>] credit2.c#csched2_alloc_udata+0x58/0xfc (PC)
>> (XEN)    [<0000000000234c80>] credit2.c#csched2_alloc_udata+0x28/0xfc (LR)
>> (XEN)    [<0000000000242d38>] sched_move_domain+0x144/0x6c0
>> (XEN)    [<000000000022dd18>] cpupool.c#cpupool_move_domain_locked+0x38/0x70
>> (XEN)    [<000000000022fadc>] cpupool_do_sysctl+0x73c/0x780
>> (XEN)    [<000000000022d8e0>] do_sysctl+0x788/0xa58
>> (XEN)    [<0000000000273b68>] traps.c#do_trap_hypercall+0x78/0x170
>> (XEN)    [<0000000000274f70>] do_trap_guest_sync+0x138/0x618
>> (XEN)    [<0000000000260458>] entry.o#guest_sync_slowpath+0xa4/0xd4
>> After some debugging I found out that unit->vcpu_list is NULL after 
>> unit->vcpu_list = d->vcpu[unit->unit_id]; with unit_id 0 in 
>> common/sched/core.c:688
>> This makes the call to is_idle_unit(unit) in csched2_alloc_udata trigger the 
>> crash.
> 
> So there is no vcpu 0 in that domain? How is this possible?

No idea, I will need to dig deeper as the state I come to does not make sense.

Could you just confirm that my operations are right and this should work before 
I start digging ?

Cheers
Bertrand

> 
> 
> Juergen
> <OpenPGP_0xB0DE9DD628BF132F.asc>