On Fri, Sep 20, 2013 at 08:04:19PM +0200, Jan Kiszka wrote: > On 2013-09-20 19:51, Paul Gortmaker wrote: > > [Re: [PATCH 0/3] KVM: Make kvm_lock non-raw] On 16/09/2013 (Mon 18:12) Paul Gortmaker wrote: > > > >> On 13-09-16 10:06 AM, Paolo Bonzini wrote: > >>> Paul Gortmaker reported a BUG on preempt-rt kernels, due to taking the > >>> mmu_lock within the raw kvm_lock in mmu_shrink_scan. He provided a > >>> patch that shrunk the kvm_lock critical section so that the mmu_lock > >>> critical section does not nest with it, but in the end there is no reason > >>> for the vm_list to be protected by a raw spinlock. Only manipulations > >>> of kvm_usage_count and the consequent hardware_enable/disable operations > >>> are not preemptable. > >>> > >>> This small series thus splits the kvm_lock in the "raw" part and the > >>> "non-raw" part. > >>> > >>> Paul, could you please provide your Tested-by? > >> > >> Sure, I'll go back and see if I can find what triggered it in the > >> original report, and give the patches a spin on 3.4.x-rt (and probably > >> 3.10.x-rt, since that is where rt-current is presently). > > > > Seems fine on 3.4-rt. On 3.10.10-rt7 it looks like there are other > > issues, probably not explicitly related to this patchset (see below). > > > > Paul. > > -- > > > > e1000e 0000:00:19.0 eth1: removed PHC > > assign device 0:0:19.0 > > pci 0000:00:19.0: irq 43 for MSI/MSI-X > > pci 0000:00:19.0: irq 43 for MSI/MSI-X > > pci 0000:00:19.0: irq 43 for MSI/MSI-X > > pci 0000:00:19.0: irq 43 for MSI/MSI-X > > BUG: sleeping function called from invalid context at /home/paul/git/linux-rt/kernel/rtmutex.c:659 > > in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/0 > > 2 locks held by swapper/0/0: > > #0: (rcu_read_lock){.+.+.+}, at: [<ffffffff8100998a>] kvm_set_irq_inatomic+0x2a/0x4a0 > > #1: (rcu_read_lock){.+.+.+}, at: [<ffffffff81038800>] kvm_irq_delivery_to_apic_fast+0x60/0x3d0 > > irq event stamp: 6121390 > > hardirqs last enabled at (6121389): [<ffffffff819f9ae0>] restore_args+0x0/0x30 > > hardirqs last disabled at (6121390): [<ffffffff819f9a2a>] common_interrupt+0x6a/0x6f > > softirqs last enabled at (0): [< (null)>] (null) > > softirqs last disabled at (0): [< (null)>] (null) > > Preemption disabled at:[<ffffffff810ebb9a>] cpu_startup_entry+0x1ba/0x430 > > > > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.10-rt7 #2 > > Hardware name: Dell Inc. OptiPlex 990/0VNP2H, BIOS A17 03/14/2013 > > ffffffff8201c440 ffff880223603cf0 ffffffff819f177d ffff880223603d18 > > ffffffff810c90d3 ffff880214a50110 0000000000000001 0000000000000001 > > ffff880223603d38 ffffffff819f89a4 ffff880214a50110 ffff880214a50110 > > Call Trace: > > <IRQ> [<ffffffff819f177d>] dump_stack+0x19/0x1b > > [<ffffffff810c90d3>] __might_sleep+0x153/0x250 > > [<ffffffff819f89a4>] rt_spin_lock+0x24/0x60 > > [<ffffffff810ccdd6>] __wake_up+0x36/0x70 > > [<ffffffff81003bbb>] kvm_vcpu_kick+0x3b/0xd0 > > -rt lacks an atomic waitqueue for triggering VCPU wakeups on MSIs from > assigned devices directly from the host IRQ handler. We need to disable > this fast-path in -rt or introduce such an abstraction (I did this once > over 2.6.33-rt). > > IIRC, VFIO goes the slower patch via a kernel thread unconditionally, > thus cannot trigger this. AFAIK VFIO just uses eventfds and these can inject MSI interrupts directly from IRQ without going through a thread. > Only legacy device assignment is affected. > > Jan > > > [<ffffffff810371a2>] __apic_accept_irq+0x2b2/0x3a0 > > [<ffffffff810385f7>] kvm_apic_set_irq+0x27/0x30 > > [<ffffffff8103894e>] kvm_irq_delivery_to_apic_fast+0x1ae/0x3d0 > > [<ffffffff81038800>] ? kvm_irq_delivery_to_apic_fast+0x60/0x3d0 > > [<ffffffff81009a8b>] kvm_set_irq_inatomic+0x12b/0x4a0 > > [<ffffffff8100998a>] ? kvm_set_irq_inatomic+0x2a/0x4a0 > > [<ffffffff8100c5b3>] kvm_assigned_dev_msi+0x23/0x40 > > [<ffffffff8113cb38>] handle_irq_event_percpu+0x88/0x3d0 > > [<ffffffff810ebb7c>] ? cpu_startup_entry+0x19c/0x430 > > [<ffffffff8113cec8>] handle_irq_event+0x48/0x70 > > [<ffffffff8113f9b7>] handle_edge_irq+0x77/0x120 > > [<ffffffff8104c6ae>] handle_irq+0x1e/0x30 > > [<ffffffff81a035ca>] do_IRQ+0x5a/0xd0 > > [<ffffffff819f9a2f>] common_interrupt+0x6f/0x6f > > <EOI> [<ffffffff819f9ae0>] ? retint_restore_args+0xe/0xe > > [<ffffffff810ebb7c>] ? cpu_startup_entry+0x19c/0x430 > > [<ffffffff810ebb38>] ? cpu_startup_entry+0x158/0x430 > > [<ffffffff819db767>] rest_init+0x137/0x140 > > [<ffffffff819db635>] ? rest_init+0x5/0x140 > > [<ffffffff822fde18>] start_kernel+0x3af/0x3bc > > [<ffffffff822fd870>] ? repair_env_string+0x5e/0x5e > > [<ffffffff822fd5a5>] x86_64_start_reservations+0x2a/0x2c > > [<ffffffff822fd673>] x86_64_start_kernel+0xcc/0xcf > > > > ================================= > > [ INFO: inconsistent lock state ] > > 3.10.10-rt7 #2 Not tainted > > --------------------------------- > > inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage. > > swapper/0/0 [HC1[1]:SC0[0]:HE0:SE1] takes: > > (&(&(&q->lock)->lock)->wait_lock){?.+.-.}, at: [<ffffffff819f7e98>] rt_spin_lock_slowlock+0x48/0x370 > > {HARDIRQ-ON-W} state was registered at: > > [<ffffffff810fc94d>] __lock_acquire+0x69d/0x20e0 > > [<ffffffff810feaee>] lock_acquire+0x9e/0x1f0 > > [<ffffffff819f9090>] _raw_spin_lock+0x40/0x80 > > [<ffffffff819f7e98>] rt_spin_lock_slowlock+0x48/0x370 > > [<ffffffff819f89ac>] rt_spin_lock+0x2c/0x60 > > [<ffffffff810ccdd6>] __wake_up+0x36/0x70 > > [<ffffffff8109c5ce>] run_timer_softirq+0x1be/0x390 > > [<ffffffff81092a09>] do_current_softirqs+0x239/0x5b0 > > [<ffffffff81092db8>] run_ksoftirqd+0x38/0x60 > > [<ffffffff810c5d7c>] smpboot_thread_fn+0x22c/0x340 > > [<ffffffff810bbf4d>] kthread+0xcd/0xe0 > > [<ffffffff81a019dc>] ret_from_fork+0x7c/0xb0 > > irq event stamp: 6121390 > > hardirqs last enabled at (6121389): [<ffffffff819f9ae0>] restore_args+0x0/0x30 > > hardirqs last disabled at (6121390): [<ffffffff819f9a2a>] common_interrupt+0x6a/0x6f > > softirqs last enabled at (0): [< (null)>] (null) > > softirqs last disabled at (0): [< (null)>] (null) > > > > other info that might help us debug this: > > Possible unsafe locking scenario: > > > > CPU0 > > ---- > > lock(&(&(&q->lock)->lock)->wait_lock); > > <Interrupt> > > lock(&(&(&q->lock)->lock)->wait_lock); > > > > *** DEADLOCK *** > > > > 2 locks held by swapper/0/0: > > #0: (rcu_read_lock){.+.+.+}, at: [<ffffffff8100998a>] kvm_set_irq_inatomic+0x2a/0x4a0 > > #1: (rcu_read_lock){.+.+.+}, at: [<ffffffff81038800>] kvm_irq_delivery_to_apic_fast+0x60/0x3d0 > > > > stack backtrace: > > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.10-rt7 #2 > > Hardware name: Dell Inc. OptiPlex 990/0VNP2H, BIOS A17 03/14/2013 > > ffffffff8262b550 ffff880223603a40 ffffffff819f177d ffff880223603a90 > > ffffffff819ec532 0000000000000000 ffffffff00000000 ffff880200000001 > > 0000000000000002 ffffffff8201ccc0 ffffffff810f9040 0000000000000000 > > Call Trace: > > <IRQ> [<ffffffff819f177d>] dump_stack+0x19/0x1b > > [<ffffffff819ec532>] print_usage_bug.part.36+0x28b/0x29a > > [<ffffffff810f9040>] ? check_usage_backwards+0x150/0x150 > > [<ffffffff810f9dab>] mark_lock+0x28b/0x6a0 > > [<ffffffff810fcbf9>] __lock_acquire+0x949/0x20e0 > > [<ffffffff811091f2>] ? __module_text_address+0x12/0x60 > > [<ffffffff8110ea8f>] ? is_module_text_address+0x2f/0x60 > > [<ffffffff810b8408>] ? __kernel_text_address+0x58/0x80 > > [<ffffffff8104dbb2>] ? print_context_stack+0x62/0xf0 > > [<ffffffff810feaee>] lock_acquire+0x9e/0x1f0 > > [<ffffffff819f7e98>] ? rt_spin_lock_slowlock+0x48/0x370 > > [<ffffffff819f9090>] _raw_spin_lock+0x40/0x80 > > [<ffffffff819f7e98>] ? rt_spin_lock_slowlock+0x48/0x370 > > [<ffffffff819f7e98>] rt_spin_lock_slowlock+0x48/0x370 > > [<ffffffff819f89ac>] rt_spin_lock+0x2c/0x60 > > [<ffffffff810ccdd6>] __wake_up+0x36/0x70 > > [<ffffffff81003bbb>] kvm_vcpu_kick+0x3b/0xd0 > > [<ffffffff810371a2>] __apic_accept_irq+0x2b2/0x3a0 > > [<ffffffff810385f7>] kvm_apic_set_irq+0x27/0x30 > > [<ffffffff8103894e>] kvm_irq_delivery_to_apic_fast+0x1ae/0x3d0 > > [<ffffffff81038800>] ? kvm_irq_delivery_to_apic_fast+0x60/0x3d0 > > [<ffffffff81009a8b>] kvm_set_irq_inatomic+0x12b/0x4a0 > > [<ffffffff8100998a>] ? kvm_set_irq_inatomic+0x2a/0x4a0 > > [<ffffffff8100c5b3>] kvm_assigned_dev_msi+0x23/0x40 > > [<ffffffff8113cb38>] handle_irq_event_percpu+0x88/0x3d0 > > [<ffffffff810ebb7c>] ? cpu_startup_entry+0x19c/0x430 > > [<ffffffff8113cec8>] handle_irq_event+0x48/0x70 > > [<ffffffff8113f9b7>] handle_edge_irq+0x77/0x120 > > [<ffffffff8104c6ae>] handle_irq+0x1e/0x30 > > [<ffffffff81a035ca>] do_IRQ+0x5a/0xd0 > > [<ffffffff819f9a2f>] common_interrupt+0x6f/0x6f > > <EOI> [<ffffffff819f9ae0>] ? retint_restore_args+0xe/0xe > > [<ffffffff810ebb7c>] ? cpu_startup_entry+0x19c/0x430 > > [<ffffffff810ebb38>] ? cpu_startup_entry+0x158/0x430 > > [<ffffffff819db767>] rest_init+0x137/0x140 > > [<ffffffff819db635>] ? rest_init+0x5/0x140 > > [<ffffffff822fde18>] start_kernel+0x3af/0x3bc > > [<ffffffff822fd870>] ? repair_env_string+0x5e/0x5e > > [<ffffffff822fd5a5>] x86_64_start_reservations+0x2a/0x2c > > [<ffffffff822fd673>] x86_64_start_kernel+0xcc/0xcf > > -- > Siemens AG, Corporate Technology, CT RTC ITP SES-DE > Corporate Competence Center Embedded Linux -- 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