On Mon, Jul 18, 2011 at 9:18 PM, Berg, Johannes <[email protected]> wrote:
>> Today I encountered a "BUG: scheduling while atomic" from kvm.ko when
>> resuming the host from suspend-to-RAM. I captured as much of the oops as
>> was displayed on screen:
>>
>> http://vmsplice.net/~stefan/panic1.jpg
>> http://vmsplice.net/~stefan/panic2.jpg
>>
>> It looks like the iwlagn driver may have crashed in an interrupt handler and
>> the
>> kvm-related panic was triggered in the aftermath. Any ideas?
>
> This doesn't look like iwlagn is involved at all -- the fact that it comes up
> in the backtrace seems to be an artifact of backtracing not being perfect.
> The RIP points to kvm_arch_vcpu_ioctl_run+0x927 and there's no reason to
> believe that iwlagn should crash kvm.
RIP seems to be arch/x86/kvm/x86.c:vcpu_enter_guest():
preempt_disable();
kvm_x86_ops->prepare_guest_switch(vcpu);
if (vcpu->fpu_active)
kvm_load_guest_fpu(vcpu);
kvm_load_guest_xcr0(vcpu);
vcpu->mode = IN_GUEST_MODE;
/* We should set ->mode before check ->requests,
* see the comment in make_all_cpus_request.
*/
smp_mb();
local_irq_disable();
if (vcpu->mode == EXITING_GUEST_MODE || vcpu->requests
|| need_resched() || signal_pending(current)) {
vcpu->mode = OUTSIDE_GUEST_MODE;
smp_wmb();
local_irq_enable();
preempt_enable();
kvm_x86_ops->cancel_injection(vcpu);
r = 1;
goto out;
}
srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
kvm_guest_enter();
if (unlikely(vcpu->arch.switch_db_regs)) {
set_debugreg(0, 7);
set_debugreg(vcpu->arch.eff_db[0], 0);
set_debugreg(vcpu->arch.eff_db[1], 1);
set_debugreg(vcpu->arch.eff_db[2], 2);
set_debugreg(vcpu->arch.eff_db[3], 3);
}
trace_kvm_entry(vcpu->vcpu_id);
kvm_x86_ops->run(vcpu);
/*
* If the guest has used debug registers, at least dr7
* will be disabled while returning to the host.
* If we don't have active breakpoints in the host, we don't
* care about the messed up debug address registers. But if
* we have some of them active, restore the old state.
*/
if (hw_breakpoint_active())
hw_breakpoint_restore();
kvm_get_msr(vcpu, MSR_IA32_TSC, &vcpu->arch.last_guest_tsc);
vcpu->mode = OUTSIDE_GUEST_MODE;
smp_wmb();
local_irq_enable(); /* <--- boom! */
Stefan
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