On 06/22/2009 09:55 AM, Ram Pai wrote:
On Mon, 2009-06-22 at 13:12 +0800, Sheng Yang wrote:
On Saturday 20 June 2009 03:23:40 Ram Pai wrote:
I see this problem with a x86 sles10 guest running on x86_64 intel host.
If the guest is reset abruptly and rebooted, some where
before grub sequence it hangs and the following message is seen in the
logs
emulation failed (pagetable) rip 7ed5 66 60 ac 20.
I located this instruction sequence in isolinux.bin on the iso ;if that
is relevant.
I did some analysis and find that there is an ept violation, which is
handled and then the next instruction '66 60' is attempted to decode
and emulate. But decode fails. kvm continues loops in the kernel
in __vcpu_run().
the code path is
kvm_run() -> __vcpu_run() -> vcpu_enter_guest() -> kvm_handle_exit() ->
handle_ept_violation() -> kvm_mmu_page_fault() -> emulate_instruction() ->
x86_decode_insn()
Hi Ram
Seems KVM failed to emulate a unknown instruction.
00000000 6660 pushad
00000002 AC lodsb
And PUSHAD have not implemented in x86_emulate.c.
Thanks Sheng for your response,
Good. that was the conclusion i had reached reading the code. However
was not sure whether the (a) the code path should have never reached
there or (b) the code must have learnt to emulate pushad.
Sounds like (b) is the case.
With ept, the only reason to emulate is mmio. It's very unlikely that
the guest is using the pusha instruction for mmio, so the guest is
probably confused here.
Current kvm.git will return an error here, and current qemu-kvm.git will
stop the guest on error so we can debug. But the real problem likely
started much earlier, I'm not sure we'll get much useful information.
Is this problem reproducible?
But I am a little curious about why this code path was only triggered when
reset. Maybe other issue exists.
What do you want me to check? I have seen ept violation code getting
triggered a few number of times at various stages. But the one reported
above is the only case where the instruction being emulated is 66 60.
one more observation:
seen only if the /boot partition is reiserfs. I have been unable to
reproduce this with /boot being ext3.
Please try it with current sources and post the output of 'info
registers' in the monitor.
--
error compiling committee.c: too many arguments to function
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