On 18/07/18 16:12, Paul Menzel wrote: > Dear Thomas, dear Bjorn, > > > Thank you for your quick responses. > > > On 07/18/18 17:02, Thomas Gleixner wrote: >> On Wed, 18 Jul 2018, Bjorn Helgaas wrote: >>> [+cc Marc, Thomas] >> >> Uurgh. That's definitely what I need right now ... :) >> >>> On Wed, Jul 18, 2018 at 03:28:15PM +0200, Paul Menzel wrote: >>>> >>>> 93.885: [ 23.020572] BUG: unable to handle kernel NULL pointer dereference at 000000000000003c >>>> 93.885: [ 23.029011] PGD 0 P4D 0 >>>> 93.885: [ 23.031670] Oops: 0000 [#1] SMP NOPTI >>>> 93.885: [ 23.035455] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.18.0-rc5+ #1 >>>> 93.885: [ 23.042079] Hardware name: MSI MS-7A37/B350M MORTAR (MS-7A37), BIOS 1.G1 05/17/2018 >>>> 93.886: [ 23.049868] RIP: 0010:msi_set_mask_bit+0xe/0x70 >> >>>> 93.913: [ 23.049868] Code: 00 53 48 89 fb e8 12 f8 ff ff 48 89 df 5b e9 c9 fe ff ff 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 53 48 8b 47 10 48 8b 58 10 <f6> 43 3c 01 74 3c 8b 15 2e 85 21 01 31 c0 85 d2 75 25 8b 43 38 48 >> >> f6 43 3c 01 testb $0x1,0x3c(%rbx) >> >> That's: >> >> if (desc->msi_attrib.is_msix) > > Is there a tool to translate that? > >>>> 93.957: [ 23.049880] RSP: 0018:ffff9e8e5e803f78 EFLAGS: 00010046 >>>> 93.957: [ 23.049881] RAX: ffff9e8e45919000 RBX: 0000000000000000 RCX: 0000000000000000 >>>> 93.958: [ 23.049882] RDX: ffff9e8e45919000 RSI: 0000000000000001 RDI: ffff9e8e45919098 >>>> 93.958: [ 23.049882] RBP: ffff9e8e45919098 R08: 0000000000000000 R09: 0000000000000000 >>>> 93.958: [ 23.049882] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9e8e45919000 >>>> 93.958: [ 23.049883] R13: 0000000000000027 R14: 0000000000000000 R15: 0000000000000000 >>>> 93.959: [ 23.049884] FS: 0000000000000000(0000) GS:ffff9e8e5e800000(0000) knlGS:0000000000000000 >>>> 93.959: [ 23.049884] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>> 93.959: [ 23.049885] CR2: 000000000000003c CR3: 00000003fc5a4000 CR4: 00000000003406f0 >>>> 93.959: [ 23.049885] Call Trace: >>>> 93.959: [ 23.049887] <IRQ> >>>> 93.960: [ 23.049889] __irq_move_irq+0x3c/0x70 >>>> 93.960: [ 23.049892] apic_ack_irq+0x2b/0x30 >>>> 93.960: [ 23.049893] handle_edge_irq+0x7d/0x1d0 >>>> 93.960: [ 23.049895] handle_irq+0x1f/0x30 >>>> 93.960: [ 23.049898] do_IRQ+0x41/0xc0 >>>> 93.960: [ 23.049899] common_interrupt+0xf/0xf >>>> 93.961: [ 23.049900] </IRQ> >> >> and desc comes from irq_data->common->msi_desc >> >> I have no idea how that can happen for an MSI interrupt. >> >> Paul, is this reproducible? > > No, unfortunately not. I only hit this once, since I attached the serial > console. > > But I found others having the same(?) problem [1][2]. > > > Kind regards, > > Paul > > > [1]: https://lkml.org/lkml/2018/1/16/122 > "[PATCH 0/1] PCI/MSI: add NULL check before use of msi_desc" > [2]: https://marc.info/?l=linux-kernel&m=151321815226439&w=2 > "[PATCH] PCI: designware: add a check of msi_desc in irqchip" > This seems to be a very different issue. These PCI host controllers pre-allocate a bunch of irqdescs which are not bound to any MSI yet (this occurs much later, when the interrupt is actually allocated to a device). But the kexec code tries to mask all interrupts, including some of these half baked interrupts, and bad things happen. This is very much a case of "don't do that". Unless I'm grossly mistaken, this isn't what happens in your case (the interrupt is very much active, but the msi_desc pointer has vanished). M. -- Jazz is not dead. It just smells funny...
