Re: [syzbot] [kvm?] [kvm-x86?] INFO: rcu detected stall in kvm_vcpu_ioctl (4)

[Hillf Danton]

> Date: Fri, 26 Dec 2025 19:34:18 -0800	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    cc3aa43b44bd Add linux-next specific files for 20251219
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1252109a580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f7a09bf3b9133d9d
> dashboard link: https://syzkaller.appspot.com/bug?extid=3d5461510f8dc4adfe30
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14eb1022580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13cc18fc580000

#syz test

--- x/arch/x86/kvm/hyperv.c
+++ y/arch/x86/kvm/hyperv.c
@@ -657,10 +657,8 @@ static int stimer_start(struct kvm_vcpu_
 					stimer->index,
 					time_now, stimer->exp_time);
 
-		hrtimer_start(&stimer->timer,
-			      ktime_add_ns(ktime_now,
-					   100 * (stimer->exp_time - time_now)),
-			      HRTIMER_MODE_ABS);
+		hrtimer_forward_now(&stimer->timer,
+				    ns_to_ktime(100 * (stimer->exp_time - time_now)));
 		return 0;
 	}
 	stimer->exp_time = stimer->count;
@@ -679,9 +677,7 @@ static int stimer_start(struct kvm_vcpu_
 					   stimer->index,
 					   time_now, stimer->count);
 
-	hrtimer_start(&stimer->timer,
-		      ktime_add_ns(ktime_now, 100 * (stimer->count - time_now)),
-		      HRTIMER_MODE_ABS);
+	hrtimer_forward_now(&stimer->timer, ns_to_ktime(100 * (stimer->count - time_now)));
 	return 0;
 }
 
--