Mapping magic page from host side

* Mapping magic page from host side
@ 2012-05-29 14:54 cs5070214
  2012-05-29 15:13 ` Bhushan Bharat-R65777
  2012-05-29 16:24 ` Sethi Varun-B16395
  0 siblings, 2 replies; 3+ messages in thread
From: cs5070214 @ 2012-05-29 14:54 UTC (permalink / raw)
  To: kvm-ppc

Hi,

   We are trying to do the patching of the privileged instructions of 
guest from host side (instead of guest kernel patching itself). For this 
we first need to map the magic page which is currently being done via 
hypercall from guest.

We tried a few approaches. When we map the magic page in the emulation 
code for the first exit due to MTMSR, it works and guest boots fine. But 
if we try to map the page on the first exit due to any privileged exits, 
the guest does not boot and it gives an error.

======================================Oops: Kernel access of bad area, sig: 11 [#1]
SMP NR_CPUS=8 P2020 RDB
Modules linked in:
NIP: c005811c LR: c0052284 CTR: c02e59cc
REGS: d81dd9b0 TRAP: 0300   Not tainted  (3.0.0-rc4-g832abe3-dirty)
MSR: 00029200 <EE,ME,CE,DE>  CR: 22000024  XER: 20000000
DEAR: e11cec14, ESR: 00000000
TASK = dc902a00[1267] 'qemu-system-ppc' THREAD: d81dc000 CPU: 0
GPR00: e104a7d0 d81dda60 dc902a00 d8090000 e11cec10 c0510000 c02e68f8 
277420
GPR08: c06f5290 d80cfffc c0720558 d81dda70 82000024 00000000 d8090000 
000000
GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
000000
GPR24: 00000000 00000000 c0720000 c0510000 d99c0000 d8090000 0000f000 
d81dda
NIP [c005811c] kvmppc_mmu_xlate+0x40/0xc4
LR [c0052284] kvmppc_read_guest+0x48/0xb0
======================================
My question is are there any prerequisites that needs to be satisfied 
before we map the magic page and what would be the proper place to do 
it?

Thanks and Regards,
Dushyant Bansal

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