Hollis Blanchard wrote:
> On Thu, 2008-03-13 at 18:53 +0100, Christian Ehrhardt wrote:
>> ok for Hollis to continue and anyone else that might have comments
>> -> tracking any eviction of the guest kernel mapping (=0xC..) did not
>> trigger
>> -> tracking the delivery of a itlb/dtlb miss with that address did not
>> trigger
>> -> I inserted a BUG statement in the guests report of "Unable to
>> handle kernel paging request ..."
>>    That triggers a emulation of a trap in the host and there I have a
>> dump_vcpu&dump_tlb
>>
> I think this just means our debug tests in the host kernel aren't
> working. The *only* way the guest interrupt vectors are invoked is by
> the host kernel...
> 
right - I checked and changed the eaddr matching and now get useful triggers.
And you now can see the initial programming of the Kernel mapping done by the guest (3x tlbwe). I add the output here for reference, but unfortunately now that I have triggers that are known to work the actual issue does no more occur :-(. I run into some soft lockup all the time now (12/12 tests).
Maybe we need to fix that first (if is not related anyway)?
I attach an updated version of the debug patch for the host kernel.

I only post vcpu (all zero gpr lines removed) and tlb dump, not the stack trace because this tlb programming is expected:

kvmppc_emul_tlbwe - writing or evicting guest kernel mapping
 63: tid 00000000 w0 00000000 w1 00000000 w2 00000000,
 inst: ra 00000000 rs 00000003 ws 00000000
 guest address: 0x0
pc:   000000a4 msr:  00000040
lr:   0000003c ctr:  00000000
srr0: 00000000 srr1: 00000000
dear: 00000000 esr:  00000000
exceptions: 00000000
gpr00: 0000003f 00fffff8 00000000 c0000290
gpr04: 00000000 00000107 00000000 00000000
gpr28: 00000000 00000000 00000000 00263100
vcpu 0 TLB dump:
| nr |     tid  |    word0 |    word1 |    word2 |
G 0 | 00000000 | 00000270 | 00000000 | 00000007 |
S42 | 00000000 | 00000310 | 0E622000 | 0000003F |
[...]
kvmppc_emul_tlbwe - writing or evicting guest kernel mapping
 63: tid 00000000 w0 c0000290 w1 00000000 w2 00000000,
 inst: ra 00000000 rs 00000004 ws 00000001
pc:   000000a8 msr:  00000040
lr:   0000003c ctr:  00000000
srr0: 00000000 srr1: 00000000
dear: 00000000 esr:  00000000
exceptions: 00000000
gpr00: 0000003f 00fffff8 00000000 c0000290
gpr04: 00000000 00000107 00000000 00000000
gpr28: 00000000 00000000 00000000 00263100
vcpu 0 TLB dump:
| nr |     tid  |    word0 |    word1 |    word2 |
G 0 | 00000000 | 00000270 | 00000000 | 00000007 |
G63 | 00000000 | C0000290 | 00000000 | 00000000 |
S42 | 00000000 | 00000310 | 0E622000 | 0000003F |
S43 | 00000000 | C0000310 | 0E622000 | 00000007 |
[...]
kvmppc_emul_tlbwe - writing or evicting guest kernel mapping
 63: tid 00000000 w0 c0000290 w1 00000000 w2 00000000,
 inst: ra 00000000 rs 00000005 ws 00000002
pc:   000000ac msr:  00000040
lr:   0000003c ctr:  00000000
srr0: 00000000 srr1: 00000000
dear: 00000000 esr:  00000000
exceptions: 00000000
gpr00: 0000003f 00fffff8 00000000 c0000290
gpr04: 00000000 00000107 00000000 00000000
gpr28: 00000000 00000000 00000000 00263100
vcpu 0 TLB dump:
| nr |     tid  |    word0 |    word1 |    word2 |
G 0 | 00000000 | 00000270 | 00000000 | 00000007 |
G63 | 00000000 | C0000290 | 00000000 | 00000000 |
S42 | 00000000 | 00000310 | 0E622000 | 0000003F |
S44 | 00000000 | C0000310 | 0E622000 | 00000007 |


And later only the soft lockup in 12/12 guest test runs (without that debug code, even with the non triggering one, at least 1/3 triggered the tlb issue).
Heisenberg affects bugs as it does with quantum effects ;-)
 
BUG: soft lockup - CPU#0 stuck for 61s! [modprobe:677]
NIP: c0000ac0 LR: 48008904 CTR: 00001fe6
REGS: bf896750 TRAP: 0901   Not tainted  (2.6.25-rc3)
MSR: 00021000 <ME>  CR: 44004028  XER: 20000000
TASK = c89de000[677] 'modprobe' THREAD: c89b0000
GPR00: 00000003 bf896800 00000000 0feb86a2 0feb5d45 00000073 0000005f feff0000
GPR08: 00000000 00000000 00000000 0fea919c 42000024
NIP [c0000ac0] Decrementer+0x0/0xc0
LR [48008904] 0x48008904
Call Trace:
Instruction dump:
914b00b0 3d400002 614a1002 512a0420 4800c471 c000ba60 c000d6e0 60000000
60000000 60000000 60000000 60000000 <7d5043a6> 7d7143a6 7c3443a6 7d400026


-- 

Grüsse / regards, 
Christian Ehrhardt
IBM Linux Technology Center, Open Virtualization