On 4/20/2024 9:03 AM, David Woodhouse wrote: > On Fri, 2024-04-19 at 16:54 -0700, Chen, Zide wrote: >> >> However, the selftest hangs: >> >> [Apr19 16:15] kselftest: Running tests in kvm >> [Apr19 16:16] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: >> [ +0.000628] rcu: 78-...0: (1 GPs behind) idle=3c8c/1/0x4000000000000000 softirq=5908/5913 fqs=14025 >> [ +0.000468] rcu: (detected by 104, t=60003 jiffies, g=60073, q=3100 ncpus=128) >> [ +0.000389] Sending NMI from CPU 104 to CPUs 78: >> [ +0.000360] NMI backtrace for cpu 78 >> [ +0.000004] CPU: 78 PID: 33515 Comm: pvclock_test Tainted: G O 6.9.0-rc1zide-l0+ #194 >> [ +0.000003] Hardware name: Inspur NF5280M7/NF5280M7, BIOS 05.08.01 08/18/2023 >> [ +0.000002] RIP: 0010:pvclock_update_vm_gtod_copy+0xb5/0x200 [kvm] > > Ah, kvm_get_time_scale() doesn't much like being asked to scale to zero. > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index a07b60351894..45fb99986cf9 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3046,7 +3046,8 @@ static void pvclock_update_vm_gtod_copy(struct kvm *kvm) > * Copy from the field protected solely by ka->tsc_write_lock, > * to the field protected by the ka->pvclock_sc seqlock. > */ > - ka->master_tsc_scaling_ratio = ka->last_tsc_scaling_ratio; > + ka->master_tsc_scaling_ratio = ka->last_tsc_scaling_ratio ? : > + kvm_caps.default_tsc_scaling_ratio; > > /* > * Calculate the scaling factors precisely the same way > * that kvm_guest_time_update() does. > last_tsc_hz = kvm_scale_tsc(tsc_khz * 1000, > ka->last_tsc_scaling_ratio); Should be ka->master_tsc_scaling_ratio? If I restored the KVM_REQ_GLOBAL_CLOCK_UPDATE request from kvm_arch_vcpu_load(), the selftest works for me, and I ran the test for 1000+ iterations, w/ or w/o TSC scaling, the TEST_ASSERT(delta_corrected <= ±1) never got hit. This is awesome! However, without KVM_REQ_GLOBAL_CLOCK_UPDATE, it still fails on creating a VM. Maybe the init sequence sill needs some rework. BUG: unable to handle page fault for address: 005b29e3f221ccf0 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 86 PID: 4118 Comm: pvclock_test Tainted Hardware name: Inspur NF5280M7/NF5280M7, BIOS 05.08.01 08/18/2023 RIP: 0010:start_creating+0x80/0x190 Code: ce ad 48 c7 c6 70 a1 ce ad 48 c7 c7 80 1c 9b ab e8 b5 10 d5 ff 4c 63 e0 45 85 e4 0f 85 cd 00 00 00 48 85 db 0f 84 b5 00 00 00 <48> 8b 43 30 48 8d b8 b8 > RSP: 0018:ff786eaacf3cfdd0 EFLAGS: 00010206 RAX: 0000000000000000 RBX: 005b29e3f221ccc0 RCX: 0000000000000000 RDX: 0000000000000001 RSI: ffffffffadcea170 RDI: 0000000000000000 RBP: ffffffffc06ac8cf R08: ffffffffa6ea0fe0 R09: ffffffffc06a5940 R10: ff786eaacf3cfe30 R11: 00000013a7b5feaa R12: 0000000000000000 R13: 0000000000000124 R14: ff786eaacfa11000 R15: 00000000000081a4 FS: 00007f0837c89740(0000) GS:ff4f44b6bfd80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0 CR2: 005b29e3f221ccf0 CR3: 000000014bdf8002 CR4: 0000000000f73ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> ? __die+0x24/0x70 ? page_fault_oops+0x81/0x150 ? do_user_addr_fault+0x64/0x6c0 ? exc_page_fault+0x8a/0x1a0 ? asm_exc_page_fault+0x26/0x30 ? start_creating+0x80/0x190 __debugfs_create_file+0x43/0x1f0 kvm_create_vm_debugfs+0x28b/0x2d0 [kvm] kvm_create_vm+0x457/0x650 [kvm] kvm_dev_ioctl+0x88/0x180 [kvm] __x64_sys_ioctl+0x8e/0xd0 do_syscall_64+0x5b/0x120 entry_SYSCALL_64_after_hwframe+0x71/0x79 RIP: 0033:0x7f0837b1a94f Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <41> 89 c0 3d 00 f0 ff ff > RSP: 002b:00007ffe01be3fc0 EFLAGS: 00000246 ORIG_RAX RAX: ffffffffffffffda RBX: 0000000000434480 RCX: 00007f0837b1a94f RDX: 0000000000000000 RSI: 000000000000ae01 RDI: 0000000000000005 RBP: 0000000000000009 R08: 000000000041b1a0 R09: 000000000041bfcf R10: 00007f0837bd8882 R11: 0000000000000246 R12: 0000000000434480 R13: 000000000041e0f0 R14: 0000000000001000 R15: 0000000000000207 </TASK> Modules linked in: kvm_intel(O) kvm(O) [last unloaded: kvm(O)] CR2: 005b29e3f221ccf0
