From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Ehrhardt Date: Wed, 12 Mar 2008 12:09:35 +0000 Subject: Re: [kvm-ppc-devel] Guests oops when trying to mount initramfs Message-Id: <47D7C7FF.2060306@linux.vnet.ibm.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: kvm-ppc@vger.kernel.org Hi, I already chatted with Hollis a bit about that, but wanted to ask you about= it. I also put kvm-ppc-devel on cc because it seem to be a common issue. I as well as Hollis saw that kind of bug in the past occasionally but never= in a reproducible way to be able to debug it. So the first question is - is your scenario running into that bug to ~>95% ? And if it reproducible in your case we can use it to find the reason for it= , here a short summary from my past discussions about that issue: - effectively what you see is that the guest has an itlb miss for it's kern= el mapping. - we only deliver that to the guest if we can't find that mapping in the gu= est tlb - this should never happen because the guest should never remove it's own k= ernel mapping and therefor we should be able to cover all itlb misses in th= e host by using the guest tlb - but it happens so the question is when&why is the guest kernel mapping re= moved from the guest tlb - afaik we have only one place that might remove that mapping which is the = function kvmppc_emul_tlbwe - we also know the kernel mapping which is usually a single 16mb mapping we= initialize for the guest in kvm_arch_vcpu_setup (I might be wrong here - H= ollis?) =3D> we could track that tlbwe that should never happen by inserting a warn= _on into kvmppc_emul_tlbwe if it overwrites a guest tlb kernel mapping and = starting from there debug whats going on Any comments or other suggestions are welcome Jerone Young wrote: > I'm looking into this. But got a guest to load without the device tree > mainpulation code. I have an cuImage with a prefilled device tree built > in & initramfs integrated.=20 >=20 > It oopses at Decrementor()=20 >=20 > Does not mount the initramfs=20 >=20 > Here is the trace: >=20 [...] > RPC: Registered udp transport module. > RPC: Registered tcp transport module. > Freeing unused kernel memory: 1500k init > Unable to handle kernel paging request for instruction fetch > Faulting instruction address: 0xc0000ac0 > Oops: Kernel access of bad area, sig: 1 [#1] > Bamboo > Modules linked in: > NIP: c0000ac0 LR: 48003fdc CTR: 00000000 > REGS: bfcfe910 TRAP: 0400 Not tainted (2.6.25-rc3-dirty) > MSR: 00021000 CR: 42000028 XER: 00000000 > TASK =3D c8810400[1] 'init' THREAD: c881e000 > GPR00: 00000001 bfcfe9c0 00000000 480177b0 4801795c 00000001 00000000 > 48011f34=20 > GPR08: 0002d002 48026e64 00000000 bfcfe9c0 c881e000 00000000 00000000 > 00000000=20 > GPR16: 00000000 48018700 00000001 c0240000 c0240000 bfcfea48 00000007 > 10000034=20 > GPR24: 00000000 6fffff40 48017000 48027f4c 00000000 480177b0 480272e4 > bfcfe9c0=20 > NIP [c0000ac0] Decrementer+0x0/0xc0 > LR [48003fdc] 0x48003fdc > Call Trace: > Instruction dump: > 914b00b0 3d400002 614a1002 512a0420 4800c6b5 c000b378 c000d924 60000000=20 > 60000000 60000000 60000000 60000000 <7d5043a6> 7d7143a6 7c3443a6 > 7d400026=20 > ---[ end trace 59dad6c3a6e54fa0 ]--- --=20 Gr=FCsse / regards,=20 Christian Ehrhardt IBM Linux Technology Center, Open Virtualization ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-ppc-devel mailing list kvm-ppc-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-ppc-devel