On Tue, Jul 19, 2011 at 12:04:21PM +0300, Avi Kivity wrote: > On 07/19/2011 12:51 AM, Stefan Hajnoczi wrote: > >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! */ > > Preemption is still disabled at this point. Where does the > "scheduling while atomic" come from? Nothing in this area attempts > to schedule. > 0x10000000 in preemption counter is PREEMPT_ACTIVE, so this looks like preemptable kernel tries to preempt itself.
> The preemption counter is 0x10000100, indicating zero preempt depth > (wrong for this point, should be 1), and 1 softirq depth (doesn't > make much sense). Looks very wrong, like the preempt mixup that > occured on some archs that are not x86_64 recently. > > Can you post some disassembly around %rip? > > -- > error compiling committee.c: too many arguments to function > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
