Re: kernel bug in kvm_intel

From: Avi Kivity
Date: Sun Nov 01 2009 - 06:41:24 EST

On 11/01/2009 12:45 PM, Tejun Heo wrote:

Avi Kivity wrote:
We get a page fault immediately (next instruction) after returning from
the guest when running with oprofile. The page fault address does not
match anything the instruction does, so presumably it is one of the
accesses the processor performs in order to service an NMI (ordinary
interrupts are masked; and the fact that it happens with oprofile
strengthens this assumption).
Ah... okay, that's tricky but IIRC faults like that can be
distinguished from regular ones via processor state, right?

Not on x86. But given that the fault address is different from %rsp (which is what the instruction accesses) and %rip, there aren't many alternatives.

Here is the code in question:

3ae7: 75 05 jne 3aee<vmx_vcpu_run+0x26a>
3ae9: 0f 01 c2 vmlaunch
3aec: eb 03 jmp 3af1<vmx_vcpu_run+0x26d>
3aee: 0f 01 c3 vmresume
3af1: 48 87 0c 24 xchg %rcx,(%rsp)
^^^ fault, but not at (%rsp)
Can you please post the full oops (including kernel debug messages
during boot) or give me a pointer to the original message?

Also, does
the faulting address coincide with any symbol?

No (at least, not in

error compiling committee.c: too many arguments to function

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