* [syzbot] [kvm-x86?] WARNING in kvm_check_and_inject_events
@ 2026-07-09 16:33 syzbot
2026-07-12 2:09 ` Forwarded: [PATCH] KVM: x86: Add debug traces to investigate irq == -1 syzbot
2026-07-12 4:36 ` Forwarded: [PATCH] KVM: x86: Add debug traces (KERN_WARNING) to investigate irq syzbot
0 siblings, 2 replies; 3+ messages in thread
From: syzbot @ 2026-07-09 16:33 UTC (permalink / raw)
To: bp, dave.hansen, hpa, kvm, linux-kernel, mingo, pbonzini, seanjc,
syzkaller-bugs, tglx, x86
Hello,
syzbot found the following issue on:
HEAD commit: 0e35b9b6ec0f Merge tag 'mm-hotfixes-stable-2026-07-06-17-4..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1144b739580000
kernel config: https://syzkaller.appspot.com/x/.config?x=48ef5c5c0f192153
dashboard link: https://syzkaller.appspot.com/bug?extid=9dcd0a11dc9703a49511
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=129d4389580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10de8432580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-0e35b9b6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c14bac7bee17/vmlinux-0e35b9b6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/36bfa5293255/bzImage-0e35b9b6.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9dcd0a11dc9703a49511@syzkaller.appspotmail.com
------------[ cut here ]------------
irq == -1
WARNING: arch/x86/kvm/x86.c:10800 at kvm_check_and_inject_events+0xf1e/0x1070 arch/x86/kvm/x86.c:10800, CPU#0: syz.2.478/7431
Modules linked in:
CPU: 0 UID: 0 PID: 7431 Comm: syz.2.478 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:kvm_check_and_inject_events+0xf1e/0x1070 arch/x86/kvm/x86.c:10800
Code: 00 48 8b 44 24 20 48 0d 00 01 01 00 48 89 44 24 10 e9 35 fd ff ff e8 51 44 7e 00 90 0f 0b 90 e9 b7 fe ff ff e8 43 44 7e 00 90 <0f> 0b 90 e9 2e f8 ff ff e8 d5 bd ee 00 e9 ae f6 ff ff 48 8b 7c 24
RSP: 0018:ffffc90003e77a20 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff8880564729c0 RCX: ffffffff818b8adc
RDX: ffff888027f40000 RSI: ffffffff818b8bfd RDI: ffff888027f40000
RBP: 00000000ffffffff R08: 0000000000000005 R09: 00000000ffffffff
R10: 00000000ffffffff R11: 0000000000000000 R12: ffff8880564735ec
R13: 0000000000000001 R14: ffff888056472ca8 R15: ffff8880564732f8
FS: 000055558b257500(0000) GS:ffff8880d5dec000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb475a73780 CR3: 0000000034df7000 CR4: 0000000000352ef0
Call Trace:
<TASK>
vcpu_enter_guest arch/x86/kvm/x86.c:11296 [inline]
vcpu_run+0xf1d/0x5d50 arch/x86/kvm/x86.c:11707
kvm_arch_vcpu_ioctl_run+0x5b6/0x1890 arch/x86/kvm/x86.c:12062
kvm_vcpu_ioctl+0x730/0x1700 virt/kvm/kvm_main.c:4470
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl fs/ioctl.c:583 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb475b9de59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc07cddbe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fb475e25fa0 RCX: 00007fb475b9de59
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 00007fb475c33e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb475e25fac R14: 00007fb475e25fa0 R15: 00007fb475e25fa0
</TASK>
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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If you want to overwrite report's subsystems, reply with:
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If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
^ permalink raw reply [flat|nested] 3+ messages in thread
* Forwarded: [PATCH] KVM: x86: Add debug traces to investigate irq == -1
2026-07-09 16:33 [syzbot] [kvm-x86?] WARNING in kvm_check_and_inject_events syzbot
@ 2026-07-12 2:09 ` syzbot
2026-07-12 4:36 ` Forwarded: [PATCH] KVM: x86: Add debug traces (KERN_WARNING) to investigate irq syzbot
1 sibling, 0 replies; 3+ messages in thread
From: syzbot @ 2026-07-12 2:09 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] KVM: x86: Add debug traces to investigate irq == -1
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Reported-by: syzbot+9dcd0a11dc9703a49511@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=9dcd0a11dc9703a49511
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
arch/x86/kvm/i8259.c | 37 ++++++++++++++++++++++++++++++++---
arch/x86/kvm/irq.c | 46 +++++++++++++++++++++++++++++++++++++++++---
2 files changed, 77 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 6a942ac622d5..4360ed7cc319 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -233,13 +233,33 @@ int kvm_pic_read_irq(struct kvm *kvm)
{
int irq, irq2, intno;
struct kvm_pic *s = kvm->arch.vpic;
-
- s->output = 0;
-
pic_lock(s);
+ printk(KERN_DEBUG
+ "KVM_DEBUG: pic_read_irq START "
+ "output=%d "
+ "IRR0=%02x IMR0=%02x "
+ "ISR0=%02x\n",
+ s->output,
+ s->pics[0].irr,
+ s->pics[0].imr,
+ s->pics[0].isr);
+ s->output = 0;
+ printk(KERN_DEBUG
+ "KVM_DEBUG: output set to 0!\n");
irq = pic_get_irq(&s->pics[0]);
+ printk(KERN_DEBUG
+ "KVM_DEBUG: pic_get_irq returned %d\n",
+ irq);
if (irq >= 0) {
pic_intack(&s->pics[0], irq);
+ printk(KERN_DEBUG
+ "KVM_DEBUG: after pic_intack "
+ "IRR0=%02x "
+ "ISR0=%02x "
+ "auto_eoi=%d\n",
+ s->pics[0].irr,
+ s->pics[0].isr,
+ s->pics[0].auto_eoi);
if (irq == 2) {
irq2 = pic_get_irq(&s->pics[1]);
if (irq2 >= 0)
@@ -253,6 +273,9 @@ int kvm_pic_read_irq(struct kvm *kvm)
} else
intno = s->pics[0].irq_base + irq;
} else {
+ printk(KERN_DEBUG
+ "KVM_DEBUG: spurious IRQ! "
+ "no irq found in IRR!\n");
/*
* spurious IRQ on host controller
*/
@@ -260,6 +283,14 @@ int kvm_pic_read_irq(struct kvm *kvm)
intno = s->pics[0].irq_base + irq;
}
pic_update_irq(s);
+ printk(KERN_DEBUG
+ "KVM_DEBUG: pic_read_irq END "
+ "intno=%d "
+ "output=%d "
+ "IRR0=%02x\n",
+ intno,
+ s->output,
+ s->pics[0].irr);
pic_unlock(s);
return intno;
diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 8c62c6d4d5c1..1c7541e01d4a 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -79,8 +79,19 @@ int kvm_cpu_has_extint(struct kvm_vcpu *v)
return 0;
#ifdef CONFIG_KVM_IOAPIC
- if (pic_in_kernel(v->kvm))
+ if (pic_in_kernel(v->kvm)) {
+ printk(KERN_DEBUG
+ "KVM_DEBUG: has_extint called "
+ "output=%d "
+ "IRR0=%02x IRR1=%02x "
+ "IMR0=%02x IMR1=%02x\n",
+ v->kvm->arch.vpic->output,
+ v->kvm->arch.vpic->pics[0].irr,
+ v->kvm->arch.vpic->pics[1].irr,
+ v->kvm->arch.vpic->pics[0].imr,
+ v->kvm->arch.vpic->pics[1].imr);
return v->kvm->arch.vpic->output;
+ }
#endif
WARN_ON_ONCE(!irqchip_split(v->kvm));
@@ -127,7 +138,24 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_cpu_has_interrupt);
*/
int kvm_cpu_get_extint(struct kvm_vcpu *v)
{
+ int result;
+ if (pic_in_kernel(v->kvm))
+ printk(KERN_DEBUG
+ "KVM_DEBUG: get_extint called "
+ "output=%d\n",
+ v->kvm->arch.vpic->output);
if (!kvm_cpu_has_extint(v)) {
+ if (pic_in_kernel(v->kvm)) {
+ printk(KERN_DEBUG
+ "KVM_DEBUG: has_extint=FALSE "
+ "returning -1! "
+ "output=%d\n",
+ v->kvm->arch.vpic->output);
+ }
+ else
+ printk(KERN_DEBUG
+ "KVM_DEBUG: has_extint=FALSE "
+ "no pic in kernel!\n");
WARN_ON(!lapic_in_kernel(v));
return -1;
}
@@ -141,8 +169,20 @@ int kvm_cpu_get_extint(struct kvm_vcpu *v)
#endif
#ifdef CONFIG_KVM_IOAPIC
- if (pic_in_kernel(v->kvm))
- return kvm_pic_read_irq(v->kvm); /* PIC */
+ if (pic_in_kernel(v->kvm)) {
+ printk(KERN_DEBUG
+ "KVM_DEBUG: calling pic_read_irq "
+ "output=%d\n",
+ v->kvm->arch.vpic->output);
+ result = kvm_pic_read_irq(v->kvm);
+ printk(KERN_DEBUG
+ "KVM_DEBUG: pic_read_irq returned "
+ "intno=%d "
+ "output=%d\n",
+ result,
+ v->kvm->arch.vpic->output);
+ return result; /* PIC */
+ }
#endif
WARN_ON_ONCE(!irqchip_split(v->kvm));
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Forwarded: [PATCH] KVM: x86: Add debug traces (KERN_WARNING) to investigate irq
2026-07-09 16:33 [syzbot] [kvm-x86?] WARNING in kvm_check_and_inject_events syzbot
2026-07-12 2:09 ` Forwarded: [PATCH] KVM: x86: Add debug traces to investigate irq == -1 syzbot
@ 2026-07-12 4:36 ` syzbot
1 sibling, 0 replies; 3+ messages in thread
From: syzbot @ 2026-07-12 4:36 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] KVM: x86: Add debug traces (KERN_WARNING) to investigate irq
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Reported-by: syzbot+9dcd0a11dc9703a49511@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=9dcd0a11dc9703a49511
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
arch/x86/kvm/i8259.c | 37 ++++++++++++++++++++++++++++++++---
arch/x86/kvm/irq.c | 46 +++++++++++++++++++++++++++++++++++++++++---
2 files changed, 77 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 6a942ac622d5..20b3b4855974 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -233,13 +233,33 @@ int kvm_pic_read_irq(struct kvm *kvm)
{
int irq, irq2, intno;
struct kvm_pic *s = kvm->arch.vpic;
-
- s->output = 0;
-
pic_lock(s);
+ printk(KERN_WARNING
+ "KVM_DEBUG: pic_read_irq START "
+ "output=%d "
+ "IRR0=%02x IMR0=%02x "
+ "ISR0=%02x\n",
+ s->output,
+ s->pics[0].irr,
+ s->pics[0].imr,
+ s->pics[0].isr);
+ s->output = 0;
+ printk(KERN_WARNING
+ "KVM_DEBUG: output set to 0!\n");
irq = pic_get_irq(&s->pics[0]);
+ printk(KERN_WARNING
+ "KVM_DEBUG: pic_get_irq returned %d\n",
+ irq);
if (irq >= 0) {
pic_intack(&s->pics[0], irq);
+ printk(KERN_WARNING
+ "KVM_DEBUG: after pic_intack "
+ "IRR0=%02x "
+ "ISR0=%02x "
+ "auto_eoi=%d\n",
+ s->pics[0].irr,
+ s->pics[0].isr,
+ s->pics[0].auto_eoi);
if (irq == 2) {
irq2 = pic_get_irq(&s->pics[1]);
if (irq2 >= 0)
@@ -253,6 +273,9 @@ int kvm_pic_read_irq(struct kvm *kvm)
} else
intno = s->pics[0].irq_base + irq;
} else {
+ printk(KERN_WARNING
+ "KVM_DEBUG: spurious IRQ! "
+ "no irq found in IRR!\n");
/*
* spurious IRQ on host controller
*/
@@ -260,6 +283,14 @@ int kvm_pic_read_irq(struct kvm *kvm)
intno = s->pics[0].irq_base + irq;
}
pic_update_irq(s);
+ printk(KERN_WARNING
+ "KVM_DEBUG: pic_read_irq END "
+ "intno=%d "
+ "output=%d "
+ "IRR0=%02x\n",
+ intno,
+ s->output,
+ s->pics[0].irr);
pic_unlock(s);
return intno;
diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 8c62c6d4d5c1..0dad5d3c5413 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -79,8 +79,19 @@ int kvm_cpu_has_extint(struct kvm_vcpu *v)
return 0;
#ifdef CONFIG_KVM_IOAPIC
- if (pic_in_kernel(v->kvm))
+ if (pic_in_kernel(v->kvm)) {
+ printk(KERN_WARNING
+ "KVM_DEBUG: has_extint called "
+ "output=%d "
+ "IRR0=%02x IRR1=%02x "
+ "IMR0=%02x IMR1=%02x\n",
+ v->kvm->arch.vpic->output,
+ v->kvm->arch.vpic->pics[0].irr,
+ v->kvm->arch.vpic->pics[1].irr,
+ v->kvm->arch.vpic->pics[0].imr,
+ v->kvm->arch.vpic->pics[1].imr);
return v->kvm->arch.vpic->output;
+ }
#endif
WARN_ON_ONCE(!irqchip_split(v->kvm));
@@ -127,7 +138,24 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_cpu_has_interrupt);
*/
int kvm_cpu_get_extint(struct kvm_vcpu *v)
{
+ int result;
+ if (pic_in_kernel(v->kvm))
+ printk(KERN_WARNING
+ "KVM_DEBUG: get_extint called "
+ "output=%d\n",
+ v->kvm->arch.vpic->output);
if (!kvm_cpu_has_extint(v)) {
+ if (pic_in_kernel(v->kvm)) {
+ printk(KERN_WARNING
+ "KVM_DEBUG: has_extint=FALSE "
+ "returning -1! "
+ "output=%d\n",
+ v->kvm->arch.vpic->output);
+ }
+ else
+ printk(KERN_WARNING
+ "KVM_DEBUG: has_extint=FALSE "
+ "no pic in kernel!\n");
WARN_ON(!lapic_in_kernel(v));
return -1;
}
@@ -141,8 +169,20 @@ int kvm_cpu_get_extint(struct kvm_vcpu *v)
#endif
#ifdef CONFIG_KVM_IOAPIC
- if (pic_in_kernel(v->kvm))
- return kvm_pic_read_irq(v->kvm); /* PIC */
+ if (pic_in_kernel(v->kvm)) {
+ printk(KERN_WARNING
+ "KVM_DEBUG: calling pic_read_irq "
+ "output=%d\n",
+ v->kvm->arch.vpic->output);
+ result = kvm_pic_read_irq(v->kvm);
+ printk(KERN_WARNING
+ "KVM_DEBUG: pic_read_irq returned "
+ "intno=%d "
+ "output=%d\n",
+ result,
+ v->kvm->arch.vpic->output);
+ return result; /* PIC */
+ }
#endif
WARN_ON_ONCE(!irqchip_split(v->kvm));
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-07-12 4:36 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-07-09 16:33 [syzbot] [kvm-x86?] WARNING in kvm_check_and_inject_events syzbot
2026-07-12 2:09 ` Forwarded: [PATCH] KVM: x86: Add debug traces to investigate irq == -1 syzbot
2026-07-12 4:36 ` Forwarded: [PATCH] KVM: x86: Add debug traces (KERN_WARNING) to investigate irq syzbot
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