| Message ID | 20240303044539.2673085-1-apanyaki@amazon.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [5.4] xen/events: close evtchn after mapping cleanup | expand |
On Sat, Mar 02, 2024 at 08:45:39PM -0800, Andrew Paniakin wrote: > From: Andrew Panyakin <apanyaki@amazon.com> > > From: Maximilian Heyne <mheyne@amazon.de> > > Commit fa765c4b4aed2d64266b694520ecb025c862c5a9 upstream > > shutdown_pirq and startup_pirq are not taking the > irq_mapping_update_lock because they can't due to lock inversion. Both > are called with the irq_desc->lock being taking. The lock order, > however, is first irq_mapping_update_lock and then irq_desc->lock. > > This opens multiple races: > - shutdown_pirq can be interrupted by a function that allocates an event > channel: > > CPU0 CPU1 > shutdown_pirq { > xen_evtchn_close(e) > __startup_pirq { > EVTCHNOP_bind_pirq > -> returns just freed evtchn e > set_evtchn_to_irq(e, irq) > } > xen_irq_info_cleanup() { > set_evtchn_to_irq(e, -1) > } > } > > Assume here event channel e refers here to the same event channel > number. > After this race the evtchn_to_irq mapping for e is invalid (-1). > > - __startup_pirq races with __unbind_from_irq in a similar way. Because > __startup_pirq doesn't take irq_mapping_update_lock it can grab the > evtchn that __unbind_from_irq is currently freeing and cleaning up. In > this case even though the event channel is allocated, its mapping can > be unset in evtchn_to_irq. > > The fix is to first cleanup the mappings and then close the event > channel. In this way, when an event channel gets allocated it's > potential previous evtchn_to_irq mappings are guaranteed to be unset already. > This is also the reverse order of the allocation where first the event > channel is allocated and then the mappings are setup. > > On a 5.10 kernel prior to commit 3fcdaf3d7634 ("xen/events: modify internal > [un]bind interfaces"), we hit a BUG like the following during probing of NVMe > devices. The issue is that during nvme_setup_io_queues, pci_free_irq > is called for every device which results in a call to shutdown_pirq. > With many nvme devices it's therefore likely to hit this race during > boot because there will be multiple calls to shutdown_pirq and > startup_pirq are running potentially in parallel. > > ------------[ cut here ]------------ > blkfront: xvda: barrier or flush: disabled; persistent grants: enabled; indirect descriptors: enabled; bounce buffer: enabled > kernel BUG at drivers/xen/events/events_base.c:499! > invalid opcode: 0000 [#1] SMP PTI > CPU: 44 PID: 375 Comm: kworker/u257:23 Not tainted 5.10.201-191.748.amzn2.x86_64 #1 > Hardware name: Xen HVM domU, BIOS 4.11.amazon 08/24/2006 > Workqueue: nvme-reset-wq nvme_reset_work > RIP: 0010:bind_evtchn_to_cpu+0xdf/0xf0 > Code: 5d 41 5e c3 cc cc cc cc 44 89 f7 e8 2b 55 ad ff 49 89 c5 48 85 c0 0f 84 64 ff ff ff 4c 8b 68 30 41 83 fe ff 0f 85 60 ff ff ff <0f> 0b 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 0f 1f 44 00 00 > RSP: 0000:ffffc9000d533b08 EFLAGS: 00010046 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000006 > RDX: 0000000000000028 RSI: 00000000ffffffff RDI: 00000000ffffffff > RBP: ffff888107419680 R08: 0000000000000000 R09: ffffffff82d72b00 > R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000001ed > R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000002 > FS: 0000000000000000(0000) GS:ffff88bc8b500000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000000 CR3: 0000000002610001 CR4: 00000000001706e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > ? show_trace_log_lvl+0x1c1/0x2d9 > ? show_trace_log_lvl+0x1c1/0x2d9 > ? set_affinity_irq+0xdc/0x1c0 > ? __die_body.cold+0x8/0xd > ? die+0x2b/0x50 > ? do_trap+0x90/0x110 > ? bind_evtchn_to_cpu+0xdf/0xf0 > ? do_error_trap+0x65/0x80 > ? bind_evtchn_to_cpu+0xdf/0xf0 > ? exc_invalid_op+0x4e/0x70 > ? bind_evtchn_to_cpu+0xdf/0xf0 > ? asm_exc_invalid_op+0x12/0x20 > ? bind_evtchn_to_cpu+0xdf/0xf0 > ? bind_evtchn_to_cpu+0xc5/0xf0 > set_affinity_irq+0xdc/0x1c0 > irq_do_set_affinity+0x1d7/0x1f0 > irq_setup_affinity+0xd6/0x1a0 > irq_startup+0x8a/0xf0 > __setup_irq+0x639/0x6d0 > ? nvme_suspend+0x150/0x150 > request_threaded_irq+0x10c/0x180 > ? nvme_suspend+0x150/0x150 > pci_request_irq+0xa8/0xf0 > ? __blk_mq_free_request+0x74/0xa0 > queue_request_irq+0x6f/0x80 > nvme_create_queue+0x1af/0x200 > nvme_create_io_queues+0xbd/0xf0 > nvme_setup_io_queues+0x246/0x320 > ? nvme_irq_check+0x30/0x30 > nvme_reset_work+0x1c8/0x400 > process_one_work+0x1b0/0x350 > worker_thread+0x49/0x310 > ? process_one_work+0x350/0x350 > kthread+0x11b/0x140 > ? __kthread_bind_mask+0x60/0x60 > ret_from_fork+0x22/0x30 > Modules linked in: > ---[ end trace a11715de1eee1873 ]--- > > Fixes: d46a78b05c0e ("xen: implement pirq type event channels") > Co-debugged-by: Andrew Panyakin <apanyaki@amazon.com> > Signed-off-by: Maximilian Heyne <mheyne@amazon.de> > [apanyaki: backport to v5.4-stable] > Signed-off-by: Andrew Paniakin <apanyaki@amazon.com> > --- > Compare to upstream patch this one does not have close_evtchn flag > because there is no need to handle static event channels. > This feature was added only in 58f6259b7a08f ("xen/evtchn: Introduce new > IOCTL to bind static evtchn") All now qeued up, thanks. greg k-h
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index 91806dc1236d..f8554d9a9f28 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -825,8 +825,8 @@ static void shutdown_pirq(struct irq_data *data) return; do_mask(info, EVT_MASK_REASON_EXPLICIT); - xen_evtchn_close(evtchn); xen_irq_info_cleanup(info); + xen_evtchn_close(evtchn); } static void enable_pirq(struct irq_data *data) @@ -869,8 +869,6 @@ static void __unbind_from_irq(unsigned int irq) if (VALID_EVTCHN(evtchn)) { unsigned int cpu = cpu_from_irq(irq); - xen_evtchn_close(evtchn); - switch (type_from_irq(irq)) { case IRQT_VIRQ: per_cpu(virq_to_irq, cpu)[virq_from_irq(irq)] = -1; @@ -883,6 +881,7 @@ static void __unbind_from_irq(unsigned int irq) } xen_irq_info_cleanup(info); + xen_evtchn_close(evtchn); } xen_free_irq(irq);