On Thu, 19 Jan 2023 15:04:49 +0000 Jonathan Cameron <jonathan.came...@huawei.com> wrote:
> On Thu, 19 Jan 2023 12:42:44 +0000 > Jonathan Cameron via <qemu-devel@nongnu.org> wrote: > > > On Wed, 18 Jan 2023 14:31:53 -0500 > > Gregory Price <gregory.pr...@memverge.com> wrote: > > > > > I apparently forgot an intro lol > > > > > > I tested the DOE linux branch with the 2023-1-11 QEMU branch with both > > > volatile, non-volatile, and "legacy" (pre-my-patch) non-volatile mode. > > > > > > 1) *In volatile mode, there are no stack traces present (during boot*) > > > > > > On Wed, Jan 18, 2023 at 02:22:08PM -0500, Gregory Price wrote: > > > > > > > > 1) No stack traces present > > > > 2) Device usage appears to work, but cxl-cli fails to create a region, i > > > > haven't checked why yet (also tried ndctl-75, same results) > > > > 3) There seems to be some other regression with the cxl_pmem_init > > > > routine, because I get a stack trace in this setup regardless of whether > > > > I apply the type-3 device commit. > > > > > > > > > > > > All tests below with the previously posted DOE linux branch. > > > > Base QEMU branch was Jonathan's 2023-1-11 > > > > > > > > > > > > DOE Branch - 2023-1-11 (HEAD) (all commits) > > > > > > > > QEMU Config: > > > > sudo /opt/qemu-cxl/bin/qemu-system-x86_64 \ > > > > -drive > > > > file=/var/lib/libvirt/images/cxl.qcow2,format=qcow2,index=0,media=disk,id=hd > > > > \ > > > > -m 3G,slots=4,maxmem=8G \ > > > > -smp 4 \ > > > > -machine type=q35,accel=kvm,cxl=on \ > > > > -enable-kvm \ > > > > -nographic \ > > > > -object memory-backend-ram,id=mem0,size=1G,share=on \ > > > > -device pxb-cxl,id=cxl.0,bus=pcie.0,bus_nr=52 \ > > > > -device cxl-rp,id=rp0,bus=cxl.0,chassis=0,slot=0 \ > > > > -device cxl-type3,bus=rp0,volatile-memdev=mem0,id=cxl-mem0 \ > > > > -M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=1G > > > > > > > > Result: This worked, but cxl-cli could not create a region (will look > > > > into this further later). > > > > > > > > > > > > > > > > > > > > When running with a persistent memory configuration, I'm seeing a > > > > kernel stack trace on cxl_pmem_init > > > > > > > > Config: > > > > sudo /opt/qemu-cxl/bin/qemu-system-x86_64 \ > > > > -drive > > > > file=/var/lib/libvirt/images/cxl.qcow2,format=qcow2,index=0,media=disk,id=hd > > > > \ > > > > -m 3G,slots=4,maxmem=4G \ > > > > -smp 4 \ > > > > -machine type=q35,accel=kvm,cxl=on \ > > > > -enable-kvm \ > > > > -nographic \ > > > > -device pxb-cxl,id=cxl.0,bus=pcie.0,bus_nr=52 \ > > > > -device cxl-rp,port=0,id=rp0,bus=cxl.0,chassis=0,slot=0 \ > > > > -object memory-backend-file,id=cxl-mem0,mem-path=/tmp/mem0,size=1G \ > > > > -object memory-backend-file,id=cxl-lsa0,mem-path=/tmp/lsa0,size=1G \ > > > > -device > > > > cxl-type3,bus=rp0,persistent-memdev=cxl-mem0,lsa=cxl-lsa0,id=cxl-pmem0 \ > > > > -M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=1G > > > > > > > > > > > > [ 62.167518] BUG: kernel NULL pointer dereference, address: > > > > 00000000000004c0 > > > > [ 62.185069] #PF: supervisor read access in kernel mode > > > > [ 62.198502] #PF: error_code(0x0000) - not-present page > > > > [ 62.211019] PGD 0 P4D 0 > > > > [ 62.220521] Oops: 0000 [#1] PREEMPT SMP PTI > > > > [ 62.233457] CPU: 3 PID: 558 Comm: systemd-udevd Not tainted > > > > 6.2.0-rc1+ #1 > > > > [ 62.252886] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS > > > > rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014 > > > > [ 62.258432] Adding 2939900k swap on /dev/zram0. Priority:100 > > > > extents:1 across:2939900k SSDscFS > > > > [ 62.285513] RIP: 0010:cxl_nvdimm_probe+0x8d/0x130 [cxl_pmem] > > > > [ 62.285529] Code: 85 c0 0f 85 90 00 00 00 f0 80 0c 24 40 f0 80 4c 24 > > > > 08 10 f0 80 4c 24 08 20 f0 80 4c 24 08 40 49 8d 84 24 b8 04 00 00 4c 89 > > > > 0 > > > > [ 62.285531] RSP: 0018:ffffacff0141fc38 EFLAGS: 00010202 > > > > [ 62.285534] RAX: ffff97a8a37b84b8 RBX: ffff97a8a37b8000 RCX: > > > > 0000000000000000 > > > > [ 62.285536] RDX: 0000000000000001 RSI: ffff97a8a37b8000 RDI: > > > > 00000000ffffffff > > > > [ 62.285537] RBP: ffff97a8a37b8000 R08: 0000000000000001 R09: > > > > 0000000000000001 > > > > [ 62.285538] R10: 0000000000000001 R11: 0000000000000000 R12: > > > > ffff97a8a37b8000 > > > > [ 62.285539] R13: ffff97a982c3dc28 R14: 0000000000000000 R15: > > > > 0000000000000000 > > > > [ 62.285541] FS: 00007f2619829580(0000) GS:ffff97a9bca00000(0000) > > > > knlGS:0000000000000000 > > > > [ 62.285542] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > > [ 62.285544] CR2: 00000000000004c0 CR3: 00000001056a8000 CR4: > > > > 00000000000006e0 > > > > [ 62.285653] Call Trace: > > > > [ 62.285656] <TASK> > > > > [ 62.285660] cxl_bus_probe+0x17/0x50 > > > > [ 62.285691] really_probe+0xde/0x380 > > > > [ 62.285695] ? pm_runtime_barrier+0x50/0x90 > > > > [ 62.285700] __driver_probe_device+0x78/0x170 > > > > [ 62.285846] driver_probe_device+0x1f/0x90 > > > > [ 62.285850] __driver_attach+0xd2/0x1c0 > > > > [ 62.285853] ? __pfx___driver_attach+0x10/0x10 > > > > [ 62.285856] bus_for_each_dev+0x76/0xa0 > > > > [ 62.285860] bus_add_driver+0x1b1/0x200 > > > > [ 62.285863] driver_register+0x89/0xe0 > > > > [ 62.285868] ? __pfx_init_module+0x10/0x10 [cxl_pmem] > > > > [ 62.285874] cxl_pmem_init+0x50/0xff0 [cxl_pmem] > > > > [ 62.285880] do_one_initcall+0x6e/0x330 > > > > [ 62.285888] do_init_module+0x4a/0x200 > > > > [ 62.285892] __do_sys_finit_module+0x93/0xf0 > > > > [ 62.285899] do_syscall_64+0x5b/0x80 > > > > [ 62.285904] ? do_syscall_64+0x67/0x80 > > > > [ 62.285906] ? asm_exc_page_fault+0x22/0x30 > > > > [ 62.285910] ? lockdep_hardirqs_on+0x7d/0x100 > > > > [ 62.285914] entry_SYSCALL_64_after_hwframe+0x72/0xdc > > > > [ 62.285917] RIP: 0033:0x7f2619b0afbd > > > > [ 62.285920] Code: 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa > > > > 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f > > > > 8 > > > > [ 62.285922] RSP: 002b:00007ffcc516bf58 EFLAGS: 00000246 ORIG_RAX: > > > > 0000000000000139 > > > > [ 62.285924] RAX: ffffffffffffffda RBX: 00005557c0dcaa60 RCX: > > > > 00007f2619b0afbd > > > > [ 62.285925] RDX: 0000000000000000 RSI: 00007f261a18743c RDI: > > > > 0000000000000006 > > > > [ 62.285926] RBP: 00007f261a18743c R08: 0000000000000000 R09: > > > > 00007f261a17bb52 > > > > [ 62.285927] R10: 0000000000000006 R11: 0000000000000246 R12: > > > > 0000000000020000 > > > > [ 62.285928] R13: 00005557c0dbbce0 R14: 0000000000000000 R15: > > > > 00005557c0dc18a0 > > > > [ 62.285932] </TASK> > > > > [ 62.285933] Modules linked in: cxl_pmem(+) snd_pcm libnvdimm > > > > snd_timer snd joydev bochs cxl_mem drm_vram_helper parport_pc soundcore > > > > drm_ttm_g > > > > [ 62.285954] CR2: 00000000000004c0 > > > > [ 62.288385] ---[ end trace 0000000000000000 ]--- > > > > [ 63.203514] RIP: 0010:cxl_nvdimm_probe+0x8d/0x130 [cxl_pmem] > > > > [ 63.203562] Code: 85 c0 0f 85 90 00 00 00 f0 80 0c 24 40 f0 80 4c 24 > > > > 08 10 f0 80 4c 24 08 20 f0 80 4c 24 08 40 49 8d 84 24 b8 04 00 00 4c 89 > > > > 0 > > > > [ 63.203565] RSP: 0018:ffffacff0141fc38 EFLAGS: 00010202 > > > > [ 63.203570] RAX: ffff97a8a37b84b8 RBX: ffff97a8a37b8000 RCX: > > > > 0000000000000000 > > > > [ 63.203572] RDX: 0000000000000001 RSI: ffff97a8a37b8000 RDI: > > > > 00000000ffffffff > > > > [ 63.203574] RBP: ffff97a8a37b8000 R08: 0000000000000001 R09: > > > > 0000000000000001 > > > > [ 63.203576] R10: 0000000000000001 R11: 0000000000000000 R12: > > > > ffff97a8a37b8000 > > > > [ 63.203577] R13: ffff97a982c3dc28 R14: 0000000000000000 R15: > > > > 0000000000000000 > > > > [ 63.203580] FS: 00007f2619829580(0000) GS:ffff97a9bca00000(0000) > > > > knlGS:0000000000000000 > > > > [ 63.203583] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > > [ 63.203585] CR2: 00000000000004c0 CR3: 00000001056a8000 CR4: > > > > 00000000000006e0 > > > > Possibly replicated. What I did was stop cxl_pmem.ko being probed > > automatically and > > added it manually later. Trace that results is certainly similar to yours. > > > > Now the MODULE_SOFTDEP() in drivers/cxl/acpi.c should stop that happening > > assuming you are letting autoloading run. > > I wonder if there is a path in which it doesn't? > > Gregory, would you mind checking if > cxl_nvb is NULL here... > https://elixir.bootlin.com/linux/v6.2-rc4/source/drivers/cxl/pmem.c#L67 > (printk before it is used should work). > > Might also be worth checking cxl_nvd and cxl_ds > but my guess is cxl_nvb is our problem (it is when I deliberate change > the load order). Whilst I still have no idea if this is the same problem, I have identified what goes wrong if there is a module probe ordering issue. https://elixir.bootlin.com/linux/v6.2-rc4/source/drivers/cxl/core/pmem.c#L306 /* * The two actions below arrange for @cxl_nvd to be deleted when either * the top-level PMEM bridge goes down, or the endpoint device goes * through ->remove(). */ device_lock(&cxl_nvb->dev); if (cxl_nvb->dev.driver) rc = devm_add_action_or_reset(&cxl_nvb->dev, cxl_nvd_unregister, cxl_nvd); else // bridge driver not loaded, so we hit this path. rc = -ENXIO; device_unlock(&cxl_nvb->dev); if (rc) /// and this one goto err_alloc; /* @cxlmd carries a reference on @cxl_nvb until cxlmd_release_nvdimm */ return devm_add_action_or_reset(&cxlmd->dev, cxlmd_release_nvdimm, cxlmd); err: put_device(dev); err_alloc: cxlmd->cxl_nvb = NULL; cxlmd->cxl_nvd = NULL; put_device(&cxl_nvb->dev); // whilst we scrub the pointers we don't actually get rid of the // cxl_nvd that we registered. Hence later load of the driver tries to // attach to that and boom because we've scrubbed these pointers here. // A quick hack is to just call device_del(&cxl_nvd->dev) if rc = -ENXIO here. // There may well be a races though.... return rc; } EXPORT_SYMBOL_NS_GPL(devm_cxl_add_nvdimm, CXL); Of course this "fix" just stops things blowing up, it doesn't leave things in a remotely useful state. If it's triggered because someone is messing with the load order that's fine. If the same issue is occurring for Gregory, not so much. Jonathan > > Jonathan > > > > > > Dan, any thoughts? > > > > There is another race that I can trigger by repeatedly injecting errors and > > causing resets, but the trace for that is very different and > > points at cxl_pmem_ctl() called via nvdimm_probe(). I was going to try > > and pin that one down a little more before posting a report but might > > as well muddy the waters :) > > > > Unable to handle kernel NULL pointer dereference at virtual address > > 0000000000000358 > > Mem abort info: > > ESR = 0x0000000096000004 > > EC = 0x25: DABT (current EL), IL = 32 bits > > SET = 0, FnV = 0 > > EA = 0, S1PTW = 0 > > FSC = 0x04: level 0 translation fault > > Data abort info: > > ISV = 0, ISS = 0x00000004 > > CM = 0, WnR = 0 > > user pgtable: 4k pages, 48-bit VAs, pgdp=0000000102e12000 > > [0000000000000358] pgd=0000000000000000, p4d=0000000000000000 > > Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP > > Modules linked in: cxl_mem cxl_port cxl_acpi cxl_pmem cxl_pci cxl_core > > CPU: 0 PID: 236 Comm: kworker/u8:3 Not tainted 6.2.0-rc3+ #598 > > Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 > > Workqueue: events_unbound async_run_entry_fn > > pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) > > pc : cxl_pmem_ctl+0x74/0x244 [cxl_pmem] > > lr : cxl_pmem_ctl+0x60/0x244 [cxl_pmem] > > sp : ffff8000089239d0 > > x29: ffff8000089239d0 x28: 0000000000000000 x27: 0000000000000000 > > x26: ffffcd4f6b263000 x25: ffffcd4f6a25d9c8 x24: 0000000000000000 > > kernel: Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP > > x23: 0000000000000000 x22: 000000000000000c x21: ffff0000c5b95400 > > x20: ffff0000c0d9ce0c x19: 0000000000000004 x18: 0000000000000000 > > x17: 0000000000000000 x16: ffffcd4f698a5fa0 x15: 0000000000000000 > > x14: 0000000000000002 x13: 0000000000000000 x12: 0000000000000000 > > x11: 0000000000000001 x10: 409e5dd45a38ef72 x9 : ffffcd4f607531f0 > > x8 : ffff0000c0d9ce80 x7 : 0000000000000000 x6 : 0000000000000000 > > x5 : ffff800008923a84 x4 : 000000000000000c x3 : ffff800008923a10 > > x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000070 > > Call trace: > > cxl_pmem_ctl+0x74/0x244 [cxl_pmem] > > nvdimm_init_nsarea+0xb8/0xdc > > nvdimm_probe+0xc0/0x1d0 > > nvdimm_bus_probe+0x90/0x200 > > really_probe+0xc8/0x3e0 > > __driver_probe_device+0x84/0x190 > > driver_probe_device+0x44/0x120 > > __device_attach_driver+0xc4/0x160 > > bus_for_each_drv+0x80/0xe0 > > __device_attach+0xa4/0x1cc > > device_initial_probe+0x1c/0x2c > > bus_probe_device+0xa4/0xb0 > > device_add+0x404/0x920 > > nd_async_device_register+0x20/0x70 > > async_run_entry_fn+0x3c/0x154 > > process_one_work+0x200/0x474 > > worker_thread+0x74/0x43c > > kthread+0x110/0x114 > > ret_from_fork+0x10/0x20 > > Code: 53067e61 f90023e0 f9417aa2 f8617860 (f941ac57) > > ---[ end trace 0000000000000000 ]--- > > > > Note this seems to have gotten harder to hit for some reason - took > > about 50 resets. > > > > I'll keep digging > > > > Jonathan > >
