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Diffstat (limited to 'results/classifier/014/none/43643137')
| -rw-r--r-- | results/classifier/014/none/43643137 | 565 |
1 files changed, 565 insertions, 0 deletions
diff --git a/results/classifier/014/none/43643137 b/results/classifier/014/none/43643137 new file mode 100644 index 00000000..76c22330 --- /dev/null +++ b/results/classifier/014/none/43643137 @@ -0,0 +1,565 @@ +KVM: 0.794 +x86: 0.791 +performance: 0.784 +hypervisor: 0.780 +debug: 0.775 +operating system: 0.773 +register: 0.767 +virtual: 0.766 +risc-v: 0.765 +semantic: 0.764 +user-level: 0.761 +device: 0.760 +permissions: 0.755 +VMM: 0.747 +arm: 0.747 +PID: 0.742 +vnc: 0.742 +TCG: 0.737 +peripherals: 0.734 +ppc: 0.728 +assembly: 0.727 +graphic: 0.721 +network: 0.709 +alpha: 0.708 +kernel: 0.707 +architecture: 0.699 +socket: 0.674 +mistranslation: 0.665 +i386: 0.662 +boot: 0.652 +files: 0.612 + +[Qemu-devel] [BUG/RFC] INIT IPI lost when VM starts + +Hi, +We encountered a problem that when a domain starts, seabios failed to online a +vCPU. + +After investigation, we found that the reason is in kvm-kmod, KVM_APIC_INIT bit +in +vcpu->arch.apic->pending_events was overwritten by qemu, and thus an INIT IPI +sent +to AP was lost. Qemu does this since libvirtd sends a âquery-cpusâ qmp command +to qemu +on VM start. + +In qemu, qmp_query_cpus-> cpu_synchronize_state-> kvm_cpu_synchronize_state-> +do_kvm_cpu_synchronize_state, qemu gets registers/vcpu_events from kvm-kmod and +sets cpu->kvm_vcpu_dirty to true, and vcpu thread in qemu will call +kvm_arch_put_registers if cpu->kvm_vcpu_dirty is true, thus pending_events is +overwritten by qemu. + +I think there is no need for qemu to set cpu->kvm_vcpu_dirty to true after +âquery-cpusâ, +and kvm-kmod should not clear KVM_APIC_INIT unconditionally. And I am not sure +whether +it is OK for qemu to set cpu->kvm_vcpu_dirty in do_kvm_cpu_synchronize_state in +each caller. + +Whatâs your opinion? + +Let me clarify it more clearly. Time sequence is that qemu handles âquery-cpusâ qmp +command, vcpu 1 (and vcpu 0) got registers from kvm-kmod (qmp_query_cpus-> +cpu_synchronize_state-> kvm_cpu_synchronize_state-> +> do_kvm_cpu_synchronize_state-> kvm_arch_get_registers), then vcpu 0 (BSP) +sends INIT-SIPI to vcpu 1(AP). In kvm-kmod, vcpu 1âs pending_eventsâs KVM_APIC_INIT +bit set. +Then vcpu 1 continue running, vcpu1 thread in qemu calls +kvm_arch_put_registers-> kvm_put_vcpu_events, so KVM_APIC_INIT bit in vcpu 1âs +pending_events got cleared, i.e., lost. + +In kvm-kmod, except for pending_events, sipi_vector may also be overwritten., +so I am not sure if there are other fields/registers in danger, i.e., those may +be modified asynchronously with vcpu thread itself. + +BTW, using a sleep like following can reliably reproduce this problem, if VM +equipped with more than 2 vcpus and starting VM using libvirtd. + +diff --git a/target/i386/kvm.c b/target/i386/kvm.c +index 55865db..5099290 100644 +--- a/target/i386/kvm.c ++++ b/target/i386/kvm.c +@@ -2534,6 +2534,11 @@ static int kvm_put_vcpu_events(X86CPU *cpu, int level) + KVM_VCPUEVENT_VALID_NMI_PENDING | KVM_VCPUEVENT_VALID_SIPI_VECTOR; + } + ++ if (CPU(cpu)->cpu_index == 1) { ++ fprintf(stderr, "vcpu 1 sleep!!!!\n"); ++ sleep(10); ++ } ++ + return kvm_vcpu_ioctl(CPU(cpu), KVM_SET_VCPU_EVENTS, &events); + } + + +On 2017/3/20 22:21, Herongguang (Stephen) wrote: +Hi, +We encountered a problem that when a domain starts, seabios failed to online a +vCPU. + +After investigation, we found that the reason is in kvm-kmod, KVM_APIC_INIT bit +in +vcpu->arch.apic->pending_events was overwritten by qemu, and thus an INIT IPI +sent +to AP was lost. Qemu does this since libvirtd sends a âquery-cpusâ qmp command +to qemu +on VM start. + +In qemu, qmp_query_cpus-> cpu_synchronize_state-> kvm_cpu_synchronize_state-> +do_kvm_cpu_synchronize_state, qemu gets registers/vcpu_events from kvm-kmod and +sets cpu->kvm_vcpu_dirty to true, and vcpu thread in qemu will call +kvm_arch_put_registers if cpu->kvm_vcpu_dirty is true, thus pending_events is +overwritten by qemu. + +I think there is no need for qemu to set cpu->kvm_vcpu_dirty to true after +âquery-cpusâ, +and kvm-kmod should not clear KVM_APIC_INIT unconditionally. And I am not sure +whether +it is OK for qemu to set cpu->kvm_vcpu_dirty in do_kvm_cpu_synchronize_state in +each caller. + +Whatâs your opinion? + +On 20/03/2017 15:21, Herongguang (Stephen) wrote: +> +> +We encountered a problem that when a domain starts, seabios failed to +> +online a vCPU. +> +> +After investigation, we found that the reason is in kvm-kmod, +> +KVM_APIC_INIT bit in +> +vcpu->arch.apic->pending_events was overwritten by qemu, and thus an +> +INIT IPI sent +> +to AP was lost. Qemu does this since libvirtd sends a âquery-cpusâ qmp +> +command to qemu +> +on VM start. +> +> +In qemu, qmp_query_cpus-> cpu_synchronize_state-> +> +kvm_cpu_synchronize_state-> +> +do_kvm_cpu_synchronize_state, qemu gets registers/vcpu_events from +> +kvm-kmod and +> +sets cpu->kvm_vcpu_dirty to true, and vcpu thread in qemu will call +> +kvm_arch_put_registers if cpu->kvm_vcpu_dirty is true, thus +> +pending_events is +> +overwritten by qemu. +> +> +I think there is no need for qemu to set cpu->kvm_vcpu_dirty to true +> +after âquery-cpusâ, +> +and kvm-kmod should not clear KVM_APIC_INIT unconditionally. And I am +> +not sure whether +> +it is OK for qemu to set cpu->kvm_vcpu_dirty in +> +do_kvm_cpu_synchronize_state in each caller. +> +> +Whatâs your opinion? +Hi Rongguang, + +sorry for the late response. + +Where exactly is KVM_APIC_INIT dropped? kvm_get_mp_state does clear the +bit, but the result of the INIT is stored in mp_state. + +kvm_get_vcpu_events is called after kvm_get_mp_state; it retrieves +KVM_APIC_INIT in events.smi.latched_init and kvm_set_vcpu_events passes +it back. Maybe it should ignore events.smi.latched_init if not in SMM, +but I would like to understand the exact sequence of events. + +Thanks, + +paolo + +On 2017/4/6 0:16, Paolo Bonzini wrote: +On 20/03/2017 15:21, Herongguang (Stephen) wrote: +We encountered a problem that when a domain starts, seabios failed to +online a vCPU. + +After investigation, we found that the reason is in kvm-kmod, +KVM_APIC_INIT bit in +vcpu->arch.apic->pending_events was overwritten by qemu, and thus an +INIT IPI sent +to AP was lost. Qemu does this since libvirtd sends a âquery-cpusâ qmp +command to qemu +on VM start. + +In qemu, qmp_query_cpus-> cpu_synchronize_state-> +kvm_cpu_synchronize_state-> +do_kvm_cpu_synchronize_state, qemu gets registers/vcpu_events from +kvm-kmod and +sets cpu->kvm_vcpu_dirty to true, and vcpu thread in qemu will call +kvm_arch_put_registers if cpu->kvm_vcpu_dirty is true, thus +pending_events is +overwritten by qemu. + +I think there is no need for qemu to set cpu->kvm_vcpu_dirty to true +after âquery-cpusâ, +and kvm-kmod should not clear KVM_APIC_INIT unconditionally. And I am +not sure whether +it is OK for qemu to set cpu->kvm_vcpu_dirty in +do_kvm_cpu_synchronize_state in each caller. + +Whatâs your opinion? +Hi Rongguang, + +sorry for the late response. + +Where exactly is KVM_APIC_INIT dropped? kvm_get_mp_state does clear the +bit, but the result of the INIT is stored in mp_state. +It's dropped in KVM_SET_VCPU_EVENTS, see below. +kvm_get_vcpu_events is called after kvm_get_mp_state; it retrieves +KVM_APIC_INIT in events.smi.latched_init and kvm_set_vcpu_events passes +it back. Maybe it should ignore events.smi.latched_init if not in SMM, +but I would like to understand the exact sequence of events. +time0: +vcpu1: +qmp_query_cpus-> cpu_synchronize_state-> kvm_cpu_synchronize_state-> +> do_kvm_cpu_synchronize_state(and set vcpu1's cpu->kvm_vcpu_dirty to true)-> +kvm_arch_get_registers(KVM_APIC_INIT bit in vcpu->arch.apic->pending_events was not set) + +time1: +vcpu0: +send INIT-SIPI to all AP->(in vcpu 0's context)__apic_accept_irq(KVM_APIC_INIT bit +in vcpu1's arch.apic->pending_events is set) + +time2: +vcpu1: +kvm_cpu_exec->(if cpu->kvm_vcpu_dirty is +true)kvm_arch_put_registers->kvm_put_vcpu_events(overwritten KVM_APIC_INIT bit in +vcpu->arch.apic->pending_events!) + +So it's a race between vcpu1 get/put registers with kvm/other vcpus changing +vcpu1's status/structure fields in the mean time, I am in worry of if there are +other fields may be overwritten, +sipi_vector is one. + +also see: +https://www.mail-archive.com/address@hidden/msg438675.html +Thanks, + +paolo + +. + +Hi Paolo, + +What's your opinion about this patch? We found it just before finishing patches +for the past two days. + + +Thanks, +-Gonglei + + +> +-----Original Message----- +> +From: address@hidden [ +mailto:address@hidden +On +> +Behalf Of Herongguang (Stephen) +> +Sent: Thursday, April 06, 2017 9:47 AM +> +To: Paolo Bonzini; address@hidden; address@hidden; +> +address@hidden; address@hidden; address@hidden; +> +wangxin (U); Huangweidong (C) +> +Subject: Re: [BUG/RFC] INIT IPI lost when VM starts +> +> +> +> +On 2017/4/6 0:16, Paolo Bonzini wrote: +> +> +> +> On 20/03/2017 15:21, Herongguang (Stephen) wrote: +> +>> We encountered a problem that when a domain starts, seabios failed to +> +>> online a vCPU. +> +>> +> +>> After investigation, we found that the reason is in kvm-kmod, +> +>> KVM_APIC_INIT bit in +> +>> vcpu->arch.apic->pending_events was overwritten by qemu, and thus an +> +>> INIT IPI sent +> +>> to AP was lost. Qemu does this since libvirtd sends a âquery-cpusâ qmp +> +>> command to qemu +> +>> on VM start. +> +>> +> +>> In qemu, qmp_query_cpus-> cpu_synchronize_state-> +> +>> kvm_cpu_synchronize_state-> +> +>> do_kvm_cpu_synchronize_state, qemu gets registers/vcpu_events from +> +>> kvm-kmod and +> +>> sets cpu->kvm_vcpu_dirty to true, and vcpu thread in qemu will call +> +>> kvm_arch_put_registers if cpu->kvm_vcpu_dirty is true, thus +> +>> pending_events is +> +>> overwritten by qemu. +> +>> +> +>> I think there is no need for qemu to set cpu->kvm_vcpu_dirty to true +> +>> after âquery-cpusâ, +> +>> and kvm-kmod should not clear KVM_APIC_INIT unconditionally. And I am +> +>> not sure whether +> +>> it is OK for qemu to set cpu->kvm_vcpu_dirty in +> +>> do_kvm_cpu_synchronize_state in each caller. +> +>> +> +>> Whatâs your opinion? +> +> Hi Rongguang, +> +> +> +> sorry for the late response. +> +> +> +> Where exactly is KVM_APIC_INIT dropped? kvm_get_mp_state does clear +> +the +> +> bit, but the result of the INIT is stored in mp_state. +> +> +It's dropped in KVM_SET_VCPU_EVENTS, see below. +> +> +> +> +> kvm_get_vcpu_events is called after kvm_get_mp_state; it retrieves +> +> KVM_APIC_INIT in events.smi.latched_init and kvm_set_vcpu_events passes +> +> it back. Maybe it should ignore events.smi.latched_init if not in SMM, +> +> but I would like to understand the exact sequence of events. +> +> +time0: +> +vcpu1: +> +qmp_query_cpus-> cpu_synchronize_state-> kvm_cpu_synchronize_state-> +> +> do_kvm_cpu_synchronize_state(and set vcpu1's cpu->kvm_vcpu_dirty to +> +true)-> kvm_arch_get_registers(KVM_APIC_INIT bit in +> +vcpu->arch.apic->pending_events was not set) +> +> +time1: +> +vcpu0: +> +send INIT-SIPI to all AP->(in vcpu 0's +> +context)__apic_accept_irq(KVM_APIC_INIT bit in vcpu1's +> +arch.apic->pending_events is set) +> +> +time2: +> +vcpu1: +> +kvm_cpu_exec->(if cpu->kvm_vcpu_dirty is +> +true)kvm_arch_put_registers->kvm_put_vcpu_events(overwritten +> +KVM_APIC_INIT bit in vcpu->arch.apic->pending_events!) +> +> +So it's a race between vcpu1 get/put registers with kvm/other vcpus changing +> +vcpu1's status/structure fields in the mean time, I am in worry of if there +> +are +> +other fields may be overwritten, +> +sipi_vector is one. +> +> +also see: +> +https://www.mail-archive.com/address@hidden/msg438675.html +> +> +> Thanks, +> +> +> +> paolo +> +> +> +> . +> +> +> + +2017-11-20 06:57+0000, Gonglei (Arei): +> +Hi Paolo, +> +> +What's your opinion about this patch? We found it just before finishing +> +patches +> +for the past two days. +I think your case was fixed by f4ef19108608 ("KVM: X86: Fix loss of +pending INIT due to race"), but that patch didn't fix it perfectly, so +maybe you're hitting a similar case that happens in SMM ... + +> +> -----Original Message----- +> +> From: address@hidden [ +mailto:address@hidden +On +> +> Behalf Of Herongguang (Stephen) +> +> On 2017/4/6 0:16, Paolo Bonzini wrote: +> +> > Hi Rongguang, +> +> > +> +> > sorry for the late response. +> +> > +> +> > Where exactly is KVM_APIC_INIT dropped? kvm_get_mp_state does clear +> +> the +> +> > bit, but the result of the INIT is stored in mp_state. +> +> +> +> It's dropped in KVM_SET_VCPU_EVENTS, see below. +> +> +> +> > +> +> > kvm_get_vcpu_events is called after kvm_get_mp_state; it retrieves +> +> > KVM_APIC_INIT in events.smi.latched_init and kvm_set_vcpu_events passes +> +> > it back. Maybe it should ignore events.smi.latched_init if not in SMM, +> +> > but I would like to understand the exact sequence of events. +> +> +> +> time0: +> +> vcpu1: +> +> qmp_query_cpus-> cpu_synchronize_state-> kvm_cpu_synchronize_state-> +> +> > do_kvm_cpu_synchronize_state(and set vcpu1's cpu->kvm_vcpu_dirty to +> +> true)-> kvm_arch_get_registers(KVM_APIC_INIT bit in +> +> vcpu->arch.apic->pending_events was not set) +> +> +> +> time1: +> +> vcpu0: +> +> send INIT-SIPI to all AP->(in vcpu 0's +> +> context)__apic_accept_irq(KVM_APIC_INIT bit in vcpu1's +> +> arch.apic->pending_events is set) +> +> +> +> time2: +> +> vcpu1: +> +> kvm_cpu_exec->(if cpu->kvm_vcpu_dirty is +> +> true)kvm_arch_put_registers->kvm_put_vcpu_events(overwritten +> +> KVM_APIC_INIT bit in vcpu->arch.apic->pending_events!) +> +> +> +> So it's a race between vcpu1 get/put registers with kvm/other vcpus changing +> +> vcpu1's status/structure fields in the mean time, I am in worry of if there +> +> are +> +> other fields may be overwritten, +> +> sipi_vector is one. +Fields that can be asynchronously written by other VCPUs (like SIPI, +NMI) must not be SET if other VCPUs were not paused since the last GET. +(Looking at the interface, we can currently lose pending SMI.) + +INIT is one of the restricted fields, but the API unconditionally +couples SMM with latched INIT, which means that we can lose an INIT if +the VCPU is in SMM mode -- do you see SMM in kvm_vcpu_events? + +Thanks. + |