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Petersen" , "linux-hyperv@vger.kernel.org" Cc: "linux-scsi@vger.kernel.org" , Linux Kernel Mailing List , Florian Bezdeka , RT , Mitchell Levy References: <0c7fb5cd-fb21-4760-8593-e04bade84744@siemens.com> From: Jan Kiszka Content-Language: en-US Autocrypt: addr=jan.kiszka@siemens.com; keydata= xsFNBGZY+hkBEACkdtFD81AUVtTVX+UEiUFs7ZQPQsdFpzVmr6R3D059f+lzr4Mlg6KKAcNZ uNUqthIkgLGWzKugodvkcCK8Wbyw+1vxcl4Lw56WezLsOTfu7oi7Z0vp1XkrLcM0tofTbClW xMA964mgUlBT2m/J/ybZd945D0wU57k/smGzDAxkpJgHBrYE/iJWcu46jkGZaLjK4xcMoBWB I6hW9Njxx3Ek0fpLO3876bszc8KjcHOulKreK+ezyJ01Hvbx85s68XWN6N2ulLGtk7E/sXlb 79hylHy5QuU9mZdsRjjRGJb0H9Buzfuz0XrcwOTMJq7e7fbN0QakjivAXsmXim+s5dlKlZjr L3ILWte4ah7cGgqc06nFb5jOhnGnZwnKJlpuod3pc/BFaFGtVHvyoRgxJ9tmDZnjzMfu8YrA +MVv6muwbHnEAeh/f8e9O+oeouqTBzgcaWTq81IyS56/UD6U5GHet9Pz1MB15nnzVcyZXIoC roIhgCUkcl+5m2Z9G56bkiUcFq0IcACzjcRPWvwA09ZbRHXAK/ao/+vPAIMnU6OTx3ejsbHn oh6VpHD3tucIt+xA4/l3LlkZMt5FZjFdkZUuAVU6kBAwElNBCYcrrLYZBRkSGPGDGYZmXAW/ VkNUVTJkRg6MGIeqZmpeoaV2xaIGHBSTDX8+b0c0hT/Bgzjv8QARAQABzSNKYW4gS2lzemth IDxqYW4ua2lzemthQHNpZW1lbnMuY29tPsLBlAQTAQoAPhYhBABMZH11cs99cr20+2mdhQqf QXvYBQJmWPvXAhsDBQkFo5qABQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEGmdhQqfQXvY zPAP/jGiVJ2VgPcRWt2P8FbByfrJJAPCsos+SZpncRi7tl9yTEpS+t57h7myEKPdB3L+kxzg K3dt1UhYp4FeIHA3jpJYaFvD7kNZJZ1cU55QXrJI3xu/xfB6VhCs+VAUlt7XhOsOmTQqCpH7 pRcZ5juxZCOxXG2fTQTQo0gfF5+PQwQYUp0NdTbVox5PTx5RK3KfPqmAJsBKdwEaIkuY9FbM 9lGg8XBNzD2R/13cCd4hRrZDtyegrtocpBAruVqOZhsMb/h7Wd0TGoJ/zJr3w3WnDM08c+RA 5LHMbiA29MXq1KxlnsYDfWB8ts3HIJ3ROBvagA20mbOm26ddeFjLdGcBTrzbHbzCReEtN++s gZneKsYiueFDTxXjUOJgp8JDdVPM+++axSMo2js8TwVefTfCYt0oWMEqlQqSqgQwIuzpRO6I ik7HAFq8fssy2cY8Imofbj77uKz0BNZC/1nGG1OI9cU2jHrqsn1i95KaS6fPu4EN6XP/Gi/O 0DxND+HEyzVqhUJkvXUhTsOzgzWAvW9BlkKRiVizKM6PLsVm/XmeapGs4ir/U8OzKI+SM3R8 VMW8eovWgXNUQ9F2vS1dHO8eRn2UqDKBZSo+qCRWLRtsqNzmU4N0zuGqZSaDCvkMwF6kIRkD ZkDjjYQtoftPGchLBTUzeUa2gfOr1T4xSQUHhPL8zsFNBGZY+hkBEADb5quW4M0eaWPIjqY6 aC/vHCmpELmS/HMa5zlA0dWlxCPEjkchN8W4PB+NMOXFEJuKLLFs6+s5/KlNok/kGKg4fITf Vcd+BQd/YRks3qFifckU+kxoXpTc2bksTtLuiPkcyFmjBph/BGms35mvOA0OaEO6fQbauiHa QnYrgUQM+YD4uFoQOLnWTPmBjccoPuiJDafzLxwj4r+JH4fA/4zzDa5OFbfVq3ieYGqiBrtj tBFv5epVvGK1zoQ+Rc+h5+dCWPwC2i3cXTUVf0woepF8mUXFcNhY+Eh8vvh1lxfD35z2CJeY txMcA44Lp06kArpWDjGJddd+OTmUkFWeYtAdaCpj/GItuJcQZkaaTeiHqPPrbvXM361rtvaw XFUzUlvoW1Sb7/SeE/BtWoxkeZOgsqouXPTjlFLapvLu5g9MPNimjkYqukASq/+e8MMKP+EE v3BAFVFGvNE3UlNRh+ppBqBUZiqkzg4q2hfeTjnivgChzXlvfTx9M6BJmuDnYAho4BA6vRh4 Dr7LYTLIwGjguIuuQcP2ENN+l32nidy154zCEp5/Rv4K8SYdVegrQ7rWiULgDz9VQWo2zAjo TgFKg3AE3ujDy4V2VndtkMRYpwwuilCDQ+Bpb5ixfbFyZ4oVGs6F3jhtWN5Uu43FhHSCqUv8 FCzl44AyGulVYU7hTQARAQABwsF8BBgBCgAmFiEEAExkfXVyz31yvbT7aZ2FCp9Be9gFAmZY +hkCGwwFCQWjmoAACgkQaZ2FCp9Be9hN3g/8CdNqlOfBZGCFNZ8Kf4tpRpeN3TGmekGRpohU bBMvHYiWW8SvmCgEuBokS+Lx3pyPJQCYZDXLCq47gsLdnhVcQ2ZKNCrr9yhrj6kHxe1Sqv1S MhxD8dBqW6CFe/mbiK9wEMDIqys7L0Xy/lgCFxZswlBW3eU2Zacdo0fDzLiJm9I0C9iPZzkJ gITjoqsiIi/5c3eCY2s2OENL9VPXiH1GPQfHZ23ouiMf+ojVZ7kycLjz+nFr5A14w/B7uHjz uL6tnA+AtGCredDne66LSK3HD0vC7569sZ/j8kGKjlUtC+zm0j03iPI6gi8YeCn9b4F8sLpB lBdlqo9BB+uqoM6F8zMfIfDsqjB0r/q7WeJaI8NKfFwNOGPuo93N+WUyBi2yYCXMOgBUifm0 T6Hbf3SHQpbA56wcKPWJqAC2iFaxNDowcJij9LtEqOlToCMtDBekDwchRvqrWN1mDXLg+av8 qH4kDzsqKX8zzTzfAWFxrkXA/kFpR3JsMzNmvextkN2kOLCCHkym0zz5Y3vxaYtbXG2wTrqJ 8WpkWIE8STUhQa9AkezgucXN7r6uSrzW8IQXxBInZwFIyBgM0f/fzyNqzThFT15QMrYUqhhW ZffO4PeNJOUYfXdH13A6rbU0y6xE7Okuoa01EqNi9yqyLA8gPgg/DhOpGtK8KokCsdYsTbk= In-Reply-To: Content-Type: text/plain; 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This is well understood and not our goal. We only need the kernel to run correctly over Hyper-V with PREEMPT-RT enabled, and that is not the case right now. Thanks, Jan PS: Who had to idea to drop a virtual UART from Gen 2 VMs? Early boot guest debugging is true fun now... > > Thanks, > Long > >> >> [ 415.140818] BUG: scheduling while atomic: stress-ng- >> iomix/1048/0x00000002 [ 415.140822] INFO: lockdep is turned off. >> [ 415.140823] Modules linked in: intel_rapl_msr intel_rapl_common >> intel_uncore_frequency_common intel_pmc_core pmt_telemetry >> pmt_discovery pmt_class intel_pmc_ssram_telemetry intel_vsec >> ghash_clmulni_intel aesni_intel rapl binfmt_misc nls_ascii nls_cp437 vfat fat >> snd_pcm hyperv_drm snd_timer drm_client_lib drm_shmem_helper snd sg >> soundcore drm_kms_helper pcspkr hv_balloon hv_utils evdev joydev drm >> configfs efi_pstore nfnetlink vsock_loopback >> vmw_vsock_virtio_transport_common hv_sock vmw_vsock_vmci_transport >> vsock vmw_vmci efivarfs autofs4 ext4 crc16 mbcache jbd2 sr_mod sd_mod >> cdrom hv_storvsc serio_raw hid_generic scsi_transport_fc hid_hyperv >> scsi_mod hid hv_netvsc hyperv_keyboard scsi_common [ 415.140846] >> Preemption disabled at: >> [ 415.140847] [] storvsc_queuecommand+0x2e1/0xbe0 >> [hv_storvsc] [ 415.140854] CPU: 8 UID: 0 PID: 1048 Comm: stress-ng-iomix >> Not tainted 6.19.0-rc7 #30 PREEMPT_{RT,(full)} [ 415.140856] Hardware >> name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V >> UEFI Release v4.1 09/04/2024 [ 415.140857] Call Trace: >> [ 415.140861] >> [ 415.140861] ? storvsc_queuecommand+0x2e1/0xbe0 [hv_storvsc] >> [ 415.140863] dump_stack_lvl+0x91/0xb0 [ 415.140870] >> __schedule_bug+0x9c/0xc0 [ 415.140875] __schedule+0xdf6/0x1300 >> [ 415.140877] ? rtlock_slowlock_locked+0x56c/0x1980 >> [ 415.140879] ? rcu_is_watching+0x12/0x60 [ 415.140883] >> schedule_rtlock+0x21/0x40 [ 415.140885] >> rtlock_slowlock_locked+0x502/0x1980 >> [ 415.140891] rt_spin_lock+0x89/0x1e0 >> [ 415.140893] hv_ringbuffer_write+0x87/0x2a0 [ 415.140899] >> vmbus_sendpacket_mpb_desc+0xb6/0xe0 >> [ 415.140900] ? rcu_is_watching+0x12/0x60 [ 415.140902] >> storvsc_queuecommand+0x669/0xbe0 [hv_storvsc] [ 415.140904] ? >> HARDIRQ_verbose+0x10/0x10 [ 415.140908] ? __rq_qos_issue+0x28/0x40 >> [ 415.140911] scsi_queue_rq+0x760/0xd80 [scsi_mod] [ 415.140926] >> __blk_mq_issue_directly+0x4a/0xc0 [ 415.140928] >> blk_mq_issue_direct+0x87/0x2b0 [ 415.140931] >> blk_mq_dispatch_queue_requests+0x120/0x440 >> [ 415.140933] blk_mq_flush_plug_list+0x7a/0x1a0 [ 415.140935] >> __blk_flush_plug+0xf4/0x150 [ 415.140940] __submit_bio+0x2b2/0x5c0 >> [ 415.140944] ? submit_bio_noacct_nocheck+0x272/0x360 >> [ 415.140946] submit_bio_noacct_nocheck+0x272/0x360 >> [ 415.140951] ext4_read_bh_lock+0x3e/0x60 [ext4] [ 415.140995] >> ext4_block_write_begin+0x396/0x650 [ext4] [ 415.141018] ? >> __pfx_ext4_da_get_block_prep+0x10/0x10 [ext4] [ 415.141038] >> ext4_da_write_begin+0x1c4/0x350 [ext4] [ 415.141060] >> generic_perform_write+0x14e/0x2c0 [ 415.141065] >> ext4_buffered_write_iter+0x6b/0x120 [ext4] [ 415.141083] >> vfs_write+0x2ca/0x570 [ 415.141087] ksys_write+0x76/0xf0 >> [ 415.141089] do_syscall_64+0x99/0x1490 [ 415.141093] ? >> rcu_is_watching+0x12/0x60 [ 415.141095] ? >> finish_task_switch.isra.0+0xdf/0x3d0 >> [ 415.141097] ? rcu_is_watching+0x12/0x60 [ 415.141098] ? >> lock_release+0x1f0/0x2a0 [ 415.141100] ? rcu_is_watching+0x12/0x60 >> [ 415.141101] ? finish_task_switch.isra.0+0xe4/0x3d0 >> [ 415.141103] ? rcu_is_watching+0x12/0x60 [ 415.141104] ? >> __schedule+0xb34/0x1300 [ 415.141106] ? >> hrtimer_try_to_cancel+0x1d/0x170 [ 415.141109] ? >> do_nanosleep+0x8b/0x160 [ 415.141111] ? >> hrtimer_nanosleep+0x89/0x100 [ 415.141114] ? >> __pfx_hrtimer_wakeup+0x10/0x10 [ 415.141116] ? >> xfd_validate_state+0x26/0x90 [ 415.141118] ? rcu_is_watching+0x12/0x60 >> [ 415.141120] ? do_syscall_64+0x1e0/0x1490 [ 415.141121] ? >> do_syscall_64+0x1e0/0x1490 [ 415.141123] ? rcu_is_watching+0x12/0x60 >> [ 415.141124] ? do_syscall_64+0x1e0/0x1490 [ 415.141125] ? >> do_syscall_64+0x1e0/0x1490 [ 415.141127] ? irqentry_exit+0x140/0x7e0 >> [ 415.141129] entry_SYSCALL_64_after_hwframe+0x76/0x7e >> >> get_cpu() disables preemption while the spinlock hv_ringbuffer_write is using >> is converted to an rt-mutex under PREEMPT_RT. >> >> Signed-off-by: Jan Kiszka >> --- >> >> This is likely just the tip of an iceberg, see specifically [1], but if you never start >> addressing it, it will continue to crash ships, even if those are only on test >> cruises (we are fully aware that Hyper-V provides no RT guarantees for >> guests). A pragmatic alternative to that would be a simple >> >> config HYPERV >> depends on !PREEMPT_RT >> >> Please share your thoughts if this fix is worth it, or if we should better stop >> looking at the next splats that show up after it. We are currently considering to >> thread some of the hv platform IRQs under PREEMPT_RT as potential next >> step. >> >> TIA! >> >> [1] >> https://lore. >> kernel.org%2Fall%2F20230809-b4-rt_preempt-fix-v1-0- >> 7283bbdc8b14%40gmail.com%2F&data=05%7C02%7Clongli%40microsoft.c >> om%7C9bcc663272304e06251908de5f42fe3b%7C72f988bf86f141af91ab2 >> d7cd011db47%7C1%7C0%7C639052938514762134%7CUnknown%7CTWF >> pbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW >> 4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=WyFA >> %2FIUPpZDcayM%2Fj7Ky8%2Bm93bey239zVWguDspSbdo%3D&reserved=0 >> >> drivers/scsi/storvsc_drv.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index >> b43d876747b7..68c837146b9e 100644 >> --- a/drivers/scsi/storvsc_drv.c >> +++ b/drivers/scsi/storvsc_drv.c >> @@ -1855,8 +1855,9 @@ static int storvsc_queuecommand(struct Scsi_Host >> *host, struct scsi_cmnd *scmnd) >> cmd_request->payload_sz = payload_sz; >> >> /* Invokes the vsc to start an IO */ >> - ret = storvsc_do_io(dev, cmd_request, get_cpu()); >> - put_cpu(); >> + migrate_disable(); >> + ret = storvsc_do_io(dev, cmd_request, smp_processor_id()); >> + migrate_enable(); >> >> if (ret) >> scsi_dma_unmap(scmnd); >> -- >> 2.51.0 -- Siemens AG, Foundational Technologies Linux Expert Center