As a quick test I added a printk to the loop, right after the while(): while (atomic_read(&completed) != needed) { printk("kvm_flush_remote_tlbs: completed = %d, needed = %d\n", atomic_read(&completed), needed); cpu_relax(); barrier(); }
This is the output right before a lockup: Oct 24 16:03:47 bldr-ccm20 kernel: kvm_flush_remote_tlbs: completed = 2, needed = 2 Oct 24 16:03:47 bldr-ccm20 kernel: kvm_flush_remote_tlbs: completed = 2, needed = 2 Oct 24 16:03:47 bldr-ccm20 kernel: kvm_flush_remote_tlbs: completed = 1, needed = 2 Oct 24 16:03:57 bldr-ccm20 last message repeated 105738 times Oct 24 16:03:57 bldr-ccm20 kernel: BUG: soft lockup detected on CPU#0! Oct 24 16:03:57 bldr-ccm20 kernel: [<c044a0b7>] softlockup_tick+0x98/0xa6 Oct 24 16:03:57 bldr-ccm20 kernel: [<c042cc98>] update_process_times+0x39/0x5c Oct 24 16:03:57 bldr-ccm20 kernel: [<c04176ec>] smp_apic_timer_interrupt+0x5c/0x64 Oct 24 16:03:57 bldr-ccm20 kernel: [<c04049bf>] apic_timer_interrupt+0x1f/0x24 Oct 24 16:03:57 bldr-ccm20 kernel: [<c0424130>] vprintk+0x288/0x2bc Oct 24 16:03:57 bldr-ccm20 kernel: [<c0459db7>] follow_page+0x168/0x1b6 Oct 24 16:03:57 bldr-ccm20 kernel: [<c04d8067>] cfq_slice_async_store+0x5/0x38 Oct 24 16:03:57 bldr-ccm20 kernel: [<c0459db7>] follow_page+0x168/0x1b6 Oct 24 16:03:57 bldr-ccm20 kernel: [<c0406406>] do_IRQ+0xa5/0xae Oct 24 16:03:57 bldr-ccm20 kernel: [<c040492e>] common_interrupt+0x1a/0x20 Oct 24 16:03:57 bldr-ccm20 kernel: [<c042417c>] printk+0x18/0x8e Oct 24 16:03:57 bldr-ccm20 kernel: [<f89a9812>] kvm_flush_remote_tlbs+0xe0/0xf2 [kvm] ... I'd like to get a solution for RHEL5, so I am attempting to backport smp_call_function_mask(). I'm open to other suggestions if you think it is corruption or the problem is somewhere else. thanks, david Avi Kivity wrote: > david ahern wrote: >> I am trying, unsuccessfully so far, to get a vm running with 4 cpus. >> It is failing with a soft lockup: >> >> BUG: soft lockup detected on CPU#3! >> [<c044a05f>] softlockup_tick+0x98/0xa6 >> [<c042ccd4>] update_process_times+0x39/0x5c >> [<c04176ec>] smp_apic_timer_interrupt+0x5c/0x64 >> [<c04049bf>] apic_timer_interrupt+0x1f/0x24 >> [<f8a3c800>] kvm_flush_remote_tlbs+0xce/0xdb [kvm] >> [<f8a41a72>] kvm_mmu_pte_write+0x1f2/0x368 [kvm] >> [<f8a3d335>] emulator_write_emulated_onepage+0x73/0xe6 [kvm] >> [<f8a4542c>] x86_emulate_insn+0x20d8/0x3348 [kvm] >> [<f8a43106>] x86_decode_insn+0x624/0x872 [kvm] >> [<f8a3d764>] emulate_instruction+0x12b/0x258 [kvm] >> [<f88af2e4>] handle_exception+0x163/0x23f [kvm_intel] >> [<f88af09b>] kvm_handle_exit+0x70/0x8a [kvm_intel] >> [<f8a3deae>] kvm_vcpu_ioctl_run+0x234/0x339 [kvm] >> [<f8a3e27f>] kvm_vcpu_ioctl+0x0/0xa8f [kvm] >> [<f8a3e33c>] kvm_vcpu_ioctl+0xbd/0xa8f [kvm] >> [<c0408f60>] save_i387+0x23f/0x273 >> [<c04db730>] __next_cpu+0x12/0x21 >> [<c041c97f>] find_busiest_group+0x177/0x462 >> [<c04031cd>] setup_sigcontext+0x10d/0x190 >> [<c0453bed>] get_page_from_freelist+0x96/0x310 >> [<c0453dfd>] get_page_from_freelist+0x2a6/0x310 >> [<c0415a5c>] flush_tlb_others+0x83/0xb3 >> [<c0415d63>] flush_tlb_page+0x74/0x77 >> [<c0454cf1>] set_page_dirty_balance+0x8/0x35 >> [<c0459c1b>] do_wp_page+0x3a5/0x3bd >> [<c042e97e>] dequeue_signal+0x2d/0x9c >> [<c045af6b>] __handle_mm_fault+0x81b/0x87b >> [<f8a3e27f>] kvm_vcpu_ioctl+0x0/0xa8f [kvm] >> [<c0479cac>] do_ioctl+0x1c/0x5d >> [<c0479f37>] vfs_ioctl+0x24a/0x25c >> [<c0479f91>] sys_ioctl+0x48/0x5f >> [<c0403eff>] syscall_call+0x7/0xb >> >> >> I am working with kvm-48, but also tried the 20071020 snapshot. The >> stuck code is kvm_flush_remote_tlbs(): >> >> while (atomic_read(&completed) != needed) { >> cpu_relax(); >> barrier(); >> } >> >> which I take to mean one of the CPUs is not ack'ing the TLB flush >> request. >> > > I don't think it's a cpu not responding. I've stared at the code for a > while (we had this before) and the actual IPI/ack is fine. > > What's probably happening is that corruption of the mmu data structures > is causing kvm_flush_remote_tlbs() to be called repeatedly. Since it's > a very slow function, the lockup detector blames it for any lockup it > sees even though it is innocent. > > [we had exactly this issue before and it was indeed fixed after an rmap > corruption was corrected] > > >> Is this is a known bug and any options to correct it? It works fine >> with 2 vcpus, but for a comparison with xen I'd like to get the vm >> working with 4. >> >> >> > > - please send (privately, it's big) an 'objdump -Sr' of mmu.o > - what guest are you running? if it's publicly available, I can try to > replicate it > - at what stage does the failure occur? if it's early on, we can try > running with AUDIT or DEBUG > - otherwise, I'll send debugging patches to try and see what's going on > ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel