On Tue, 7 Jul 2015 19:43:35 +0800 zhanghailiang <zhang.zhanghailiang@xxxxxxxxxx> wrote: > On 2015/7/7 19:23, Igor Mammedov wrote: > > On Mon, 6 Jul 2015 17:59:10 +0800 > > zhanghailiang <zhang.zhanghailiang@xxxxxxxxxx> wrote: > > > >> On 2015/7/6 16:45, Paolo Bonzini wrote: > >>> > >>> > >>> On 06/07/2015 09:54, zhanghailiang wrote: > >>>> > >>>> From host, we found that QEMU vcpu1 thread and vcpu7 thread were not > >>>> consuming any cpu (Should be in idle state), > >>>> All of VCPUs' stacks in host is like bellow: > >>>> > >>>> [<ffffffffa07089b5>] kvm_vcpu_block+0x65/0xa0 [kvm] > >>>> [<ffffffffa071c7c1>] __vcpu_run+0xd1/0x260 [kvm] > >>>> [<ffffffffa071d508>] kvm_arch_vcpu_ioctl_run+0x68/0x1a0 [kvm] > >>>> [<ffffffffa0709cee>] kvm_vcpu_ioctl+0x38e/0x580 [kvm] > >>>> [<ffffffff8116be8b>] do_vfs_ioctl+0x8b/0x3b0 > >>>> [<ffffffff8116c251>] sys_ioctl+0xa1/0xb0 > >>>> [<ffffffff81468092>] system_call_fastpath+0x16/0x1b > >>>> [<00002ab9fe1f99a7>] 0x2ab9fe1f99a7 > >>>> [<ffffffffffffffff>] 0xffffffffffffffff > >>>> > >>>> We looked into the kernel codes that could leading to the above 'Stuck' > >>>> warning, > > in current upstream there isn't any printk(...Stuck...) left since that code path > > has been reworked. > > I've often seen this on over-committed host during guest CPUs up/down torture test. > > Could you update guest kernel to upstream and see if issue reproduces? > > > > Hmm, Unfortunately, it is very hard to reproduce, and we are still trying to reproduce it. > > For your test case, is it a kernel bug? > Or is there any related patch could solve your test problem been merged into > upstream ? I don't remember all prerequisite patches but you should be able to find http://marc.info/?l=linux-kernel&m=140326703108009&w=2 "x86/smpboot: Initialize secondary CPU only if master CPU will wait for it" and then look for dependencies. > > Thanks, > zhanghailiang > > >>>> and found that the only possible is the emulation of 'cpuid' instruct in > >>>> kvm/qemu has something wrong. > >>>> But since we can’t reproduce this problem, we are not quite sure. > >>>> Is there any possible that the cupid emulation in kvm/qemu has some bug ? > >>> > >>> Can you explain the relationship to the cpuid emulation? What do the > >>> traces say about vcpus 1 and 7? > >> > >> OK, we searched the VM's kernel codes with the 'Stuck' message, and it is located in > >> do_boot_cpu(). It's in BSP context, the call process is: > >> BSP executes start_kernel() -> smp_init() -> smp_boot_cpus() -> do_boot_cpu() -> wakeup_secondary_via_INIT() to trigger APs. > >> It will wait 5s for APs to startup, if some AP not startup normally, it will print 'CPU%d Stuck' or 'CPU%d: Not responding'. > >> > >> If it prints 'Stuck', it means the AP has received the SIPI interrupt and begins to execute the code > >> 'ENTRY(trampoline_data)' (trampoline_64.S) , but be stuck in some places before smp_callin()(smpboot.c). > >> The follow is the starup process of BSP and AP. > >> BSP: > >> start_kernel() > >> ->smp_init() > >> ->smp_boot_cpus() > >> ->do_boot_cpu() > >> ->start_ip = trampoline_address(); //set the address that AP will go to execute > >> ->wakeup_secondary_cpu_via_init(); // kick the secondary CPU > >> ->for (timeout = 0; timeout < 50000; timeout++) > >> if (cpumask_test_cpu(cpu, cpu_callin_mask)) break;// check if AP startup or not > >> > >> APs: > >> ENTRY(trampoline_data) (trampoline_64.S) > >> ->ENTRY(secondary_startup_64) (head_64.S) > >> ->start_secondary() (smpboot.c) > >> ->cpu_init(); > >> ->smp_callin(); > >> ->cpumask_set_cpu(cpuid, cpu_callin_mask); ->Note: if AP comes here, the BSP will not prints the error message. > >> > >> From above call process, we can be sure that, the AP has been stuck between trampoline_data and the cpumask_set_cpu() in > >> smp_callin(), we look through these codes path carefully, and only found a 'hlt' instruct that could block the process. > >> It is located in trampoline_data(): > >> > >> ENTRY(trampoline_data) > >> ... > >> > >> call verify_cpu # Verify the cpu supports long mode > >> testl %eax, %eax # Check for return code > >> jnz no_longmode > >> > >> ... > >> > >> no_longmode: > >> hlt > >> jmp no_longmode > >> > >> For the process verify_cpu(), > >> we can only find the 'cpuid' sensitive instruct that could lead VM exit from No-root mode. > >> This is why we doubt if cpuid emulation is wrong in KVM/QEMU that leading to the fail in verify_cpu. > >> > >> From the message in VM, we know vcpu1 and vcpu7 is something wrong. > >> [ 5.060042] CPU1: Stuck ?? > >> [ 10.170815] CPU7: Stuck ?? > >> [ 10.171648] Brought up 6 CPUs > >> > >> Besides, the follow is the cpus message got from host. > >> 80FF72F5-FF6D-E411-A8C8-000000821800:/home/fsp/hrg # virsh qemu-monitor-command instance-0000000 > >> * CPU #0: pc=0x00007f64160c683d thread_id=68570 > >> CPU #1: pc=0xffffffff810301f1 (halted) thread_id=68573 > >> CPU #2: pc=0xffffffff810301e2 (halted) thread_id=68575 > >> CPU #3: pc=0xffffffff810301e2 (halted) thread_id=68576 > >> CPU #4: pc=0xffffffff810301e2 (halted) thread_id=68577 > >> CPU #5: pc=0xffffffff810301e2 (halted) thread_id=68578 > >> CPU #6: pc=0xffffffff810301e2 (halted) thread_id=68583 > >> CPU #7: pc=0xffffffff810301f1 (halted) thread_id=68584 > >> > >> Oh, i also forgot to mention in the above message that, we have bond each vCPU to different physical CPU in > >> host. > >> > >> Thanks, > >> zhanghailiang > >> > >> > >> > >> > >> -- > >> To unsubscribe from this list: send the line "unsubscribe kvm" in > >> the body of a message to majordomo@xxxxxxxxxxxxxxx > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > . > > > > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
