Paul, On Wed, 18 Jul 2018, Paul Menzel wrote: > On 07/18/18 17:02, Thomas Gleixner 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? That tool is called brain :) Seriously, what you can do is run the 'Code: ...' line through scripts/decodecode and that will show you the disassembly. Now staring at msi_set_mask_bit() makes it pretty obvious which part it is and the offset of msi_attrib in msi_desc is 0x3c, which matches the BUG: line above. You can figure that out by counting or by using pahole. Of course if you have the vmlinux around then scripts/faddr2line is what you want to use. > >>> 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. Bah. Could you please enable GENERIC_IRQ_DEBUGFS and after a successful boot up provide me the content of all files in /sys/kernel/debug/irq/ and its subfolders? I assume you have irqbalanced running, right? > But I found others having the same(?) problem [1][2]. > > [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" That's a different story as they allocate 32 interrupt descriptors in their host driver for whatever reason. That 'fix' papers over a design issue... Thanks, tglx
