* [PATCH] kvm: Fix false positive RCU usage warning
@ 2020-04-28 15:52 ` madhuparnabhowmik10
0 siblings, 0 replies; 6+ messages in thread
From: madhuparnabhowmik10 @ 2020-04-28 15:52 UTC (permalink / raw)
To: sean.j.christopherson, wanpengli, jmattson, tglx, bp, mingo
Cc: cai, paulmck, joel, frextrite, x86, kvm, linux-kernel-mentees,
linux-kernel, Madhuparna Bhowmik
From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Fix the following false positive warnings:
[ 9403.765413][T61744] =============================
[ 9403.786541][T61744] WARNING: suspicious RCU usage
[ 9403.807865][T61744] 5.7.0-rc1-next-20200417 #4 Tainted: G L
[ 9403.838945][T61744] -----------------------------
[ 9403.860099][T61744] arch/x86/kvm/mmu/page_track.c:257 RCU-list traversed in non-reader section!!
and
[ 9405.859252][T61751] =============================
[ 9405.859258][T61751] WARNING: suspicious RCU usage
[ 9405.880867][T61755] -----------------------------
[ 9405.911936][T61751] 5.7.0-rc1-next-20200417 #4 Tainted: G L
[ 9405.911942][T61751] -----------------------------
[ 9405.911950][T61751] arch/x86/kvm/mmu/page_track.c:232 RCU-list traversed in non-reader section!!
Since srcu read lock is held, these are false positive warnings.
Therefore, pass condition srcu_read_lock_held() to
list_for_each_entry_rcu().
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
---
arch/x86/kvm/mmu/page_track.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index ddc1ec3bdacd..1ad79c7aa05b 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -229,7 +229,8 @@ void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
return;
idx = srcu_read_lock(&head->track_srcu);
- hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
+ hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
+ srcu_read_lock_held(&head->track_srcu))
if (n->track_write)
n->track_write(vcpu, gpa, new, bytes, n);
srcu_read_unlock(&head->track_srcu, idx);
@@ -254,7 +255,8 @@ void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
return;
idx = srcu_read_lock(&head->track_srcu);
- hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
+ hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
+ srcu_read_lock_held(&head->track_srcu))
if (n->track_flush_slot)
n->track_flush_slot(kvm, slot, n);
srcu_read_unlock(&head->track_srcu, idx);
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [Linux-kernel-mentees] [PATCH] kvm: Fix false positive RCU usage warning
@ 2020-04-28 15:52 ` madhuparnabhowmik10
0 siblings, 0 replies; 6+ messages in thread
From: madhuparnabhowmik10 @ 2020-04-28 15:52 UTC (permalink / raw)
To: sean.j.christopherson, wanpengli, jmattson, tglx, bp, mingo
Cc: paulmck, kvm, x86, linux-kernel, Madhuparna Bhowmik, cai, joel,
linux-kernel-mentees
From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Fix the following false positive warnings:
[ 9403.765413][T61744] =============================
[ 9403.786541][T61744] WARNING: suspicious RCU usage
[ 9403.807865][T61744] 5.7.0-rc1-next-20200417 #4 Tainted: G L
[ 9403.838945][T61744] -----------------------------
[ 9403.860099][T61744] arch/x86/kvm/mmu/page_track.c:257 RCU-list traversed in non-reader section!!
and
[ 9405.859252][T61751] =============================
[ 9405.859258][T61751] WARNING: suspicious RCU usage
[ 9405.880867][T61755] -----------------------------
[ 9405.911936][T61751] 5.7.0-rc1-next-20200417 #4 Tainted: G L
[ 9405.911942][T61751] -----------------------------
[ 9405.911950][T61751] arch/x86/kvm/mmu/page_track.c:232 RCU-list traversed in non-reader section!!
Since srcu read lock is held, these are false positive warnings.
Therefore, pass condition srcu_read_lock_held() to
list_for_each_entry_rcu().
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
---
arch/x86/kvm/mmu/page_track.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index ddc1ec3bdacd..1ad79c7aa05b 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -229,7 +229,8 @@ void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
return;
idx = srcu_read_lock(&head->track_srcu);
- hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
+ hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
+ srcu_read_lock_held(&head->track_srcu))
if (n->track_write)
n->track_write(vcpu, gpa, new, bytes, n);
srcu_read_unlock(&head->track_srcu, idx);
@@ -254,7 +255,8 @@ void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
return;
idx = srcu_read_lock(&head->track_srcu);
- hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
+ hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
+ srcu_read_lock_held(&head->track_srcu))
if (n->track_flush_slot)
n->track_flush_slot(kvm, slot, n);
srcu_read_unlock(&head->track_srcu, idx);
--
2.17.1
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] kvm: Fix false positive RCU usage warning
2020-04-28 15:52 ` [Linux-kernel-mentees] " madhuparnabhowmik10
@ 2020-04-29 20:20 ` Qian Cai
-1 siblings, 0 replies; 6+ messages in thread
From: Qian Cai @ 2020-04-29 20:20 UTC (permalink / raw)
To: Madhuparna Bhowmik
Cc: Sean Christopherson, wanpengli, jmattson, Thomas Gleixner,
Borislav Petkov, Ingo Molnar, paul E. McKenney,
Joel Fernandes (Google),
Amol Grover, x86, kvm, linux-kernel-mentees, LKML, Paolo Bonzini
> On Apr 28, 2020, at 11:52 AM, madhuparnabhowmik10@gmail.com wrote:
>
> From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
>
> Fix the following false positive warnings:
>
> [ 9403.765413][T61744] =============================
> [ 9403.786541][T61744] WARNING: suspicious RCU usage
> [ 9403.807865][T61744] 5.7.0-rc1-next-20200417 #4 Tainted: G L
> [ 9403.838945][T61744] -----------------------------
> [ 9403.860099][T61744] arch/x86/kvm/mmu/page_track.c:257 RCU-list traversed in non-reader section!!
>
> and
>
> [ 9405.859252][T61751] =============================
> [ 9405.859258][T61751] WARNING: suspicious RCU usage
> [ 9405.880867][T61755] -----------------------------
> [ 9405.911936][T61751] 5.7.0-rc1-next-20200417 #4 Tainted: G L
> [ 9405.911942][T61751] -----------------------------
> [ 9405.911950][T61751] arch/x86/kvm/mmu/page_track.c:232 RCU-list traversed in non-reader section!!
>
> Since srcu read lock is held, these are false positive warnings.
> Therefore, pass condition srcu_read_lock_held() to
> list_for_each_entry_rcu().
You forgot to add KVM maintainer (adding Paolo now). On the other hand, there could be more places need to audit in x86 KVM. Not sure you want to add them together to one patch or doing separately for each file. For example,
[29179.937976][T75781] WARNING: suspicious RCU usage
[29179.942789][T75781] 5.7.0-rc3-next-20200429 #1 Tainted: G O L
[29179.949752][T75781] -----------------------------
[29179.954498][T75781] arch/x86/kvm/../../../virt/kvm/eventfd.c:472 RCU-list traversed in non-reader section!!
[29179.964768][T75781]
[29179.964768][T75781] other info that might help us debug this:
[29179.964768][T75781]
[29179.974958][T75781]
[29179.974958][T75781] rcu_scheduler_active = 2, debug_locks = 1
[29179.982961][T75781] 3 locks held by qemu-kvm/75781:
[29179.988145][T75781] #0: ffff95b3755300d0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0xbd/0x860 [kvm]
[29179.998450][T75781] #1: ffffa45946cd7e10 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x94e/0x2e50 [kvm]
[29180.009264][T75781] #2: ffffa45946cd8b98 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x92/0x290 [kvm]
[29180.020471][T75781]
[29180.020471][T75781] stack backtrace:
[29180.026318][T75781] CPU: 16 PID: 75781 Comm: qemu-kvm Tainted: G O L 5.7.0-rc3-next-20200429 #1
[29180.036480][T75781] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 03/09/2018
[29180.045765][T75781] Call Trace:
[29180.048942][T75781] dump_stack+0xab/0x100
[29180.053132][T75781] lockdep_rcu_suspicious+0xea/0xf3
[29180.058802][T75781] kvm_notify_acked_gsi+0x10d/0x120 [kvm]
[29180.065386][T75781] kvm_notify_acked_irq+0xe5/0x290 [kvm]
[29180.071529][T75781] pic_clear_isr+0xa1/0xc0 [kvm]
[29180.077118][T75781] pic_ioport_write+0x335/0x5e0 [kvm]
[29180.082453][T75781] ? do_raw_spin_lock+0x115/0x1b0
[29180.088205][T75781] picdev_write+0x7d/0x130 [kvm]
[29180.093677][T75781] picdev_master_write+0x3a/0x50 [kvm]
[29180.099730][T75781] __kvm_io_bus_write+0x147/0x180 [kvm]
[29180.105700][T75781] kvm_io_bus_write+0xfc/0x1b0 [kvm]
[29180.111701][T75781] kernel_pio+0xeb/0x110 [kvm]
[29180.116991][T75781] emulator_pio_out+0x14f/0x400 [kvm]
[29180.122342][T75781] ? __lock_acquire+0x5c2/0x23f0
[29180.127229][T75781] ? __svm_vcpu_run+0x95/0x110 [kvm_amd]
[29180.133481][T75781] kvm_fast_pio+0x12f/0x200 [kvm]
[29180.138733][T75781] io_interception+0xba/0xe0 [kvm_amd]
[29180.144164][T75781] ? svm_sync_dirty_debug_regs+0x170/0x170 [kvm_amd]
[29180.150843][T75781] handle_exit+0x403/0x9f0 [kvm_amd]
[29180.156652][T75781] ? kvm_arch_vcpu_ioctl_run+0x286/0xb50 [kvm]
[29180.163648][T75781] vcpu_enter_guest+0xa08/0x2e50 [kvm]
[29180.169007][T75781] ? lock_acquire+0xcd/0x450
[29180.174364][T75781] ? kvm_skip_emulated_instruction+0x67/0x80 [kvm]
[29180.181422][T75781] kvm_arch_vcpu_ioctl_run+0x286/0xb50 [kvm]
[29180.188256][T75781] kvm_vcpu_ioctl+0x2d4/0x860 [kvm]
[29180.193391][T75781] ? __fget_light+0xa3/0x170
[29180.197879][T75781] ksys_ioctl+0x227/0xb90
[29180.202159][T75781] ? find_held_lock+0x35/0xa0
[29180.206777][T75781] __x64_sys_ioctl+0x4c/0x5d
[29180.211443][T75781] do_syscall_64+0x91/0xb10
[29180.215840][T75781] ? trace_hardirqs_off_thunk+0x1a/0x1c
[29180.221307][T75781] entry_SYSCALL_64_after_hwframe+0x49/0xb3
[29180.227100][T75781] RIP: 0033:0x7f2f5a90487b
[29180.231414][T75781] Code: 0f 1e fa 48 8b 05 0d 96 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d dd 95 2c 00 f7 d8 64 89 01 48
[29180.251241][T75781] RSP: 002b:00007f2f4b7fd678 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[29180.259660][T75781] RAX: ffffffffffffffda RBX: 00007f2f5fc31001 RCX: 00007f2f5a90487b
[29180.267730][T75781] RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000011
[29180.275619][T75781] RBP: 0000000000000001 R08: 000055c707b6fad0 R09: 00000000000000ff
[29180.283533][T75781] R10: 0000000000000001 R11: 0000000000000246 R12: 000055c707b58100
[29180.291622][T75781] R13: 0000000000000000 R14: 00007f2f5fc30000 R15: 000055c70a1b4c60
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
> ---
> arch/x86/kvm/mmu/page_track.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
> index ddc1ec3bdacd..1ad79c7aa05b 100644
> --- a/arch/x86/kvm/mmu/page_track.c
> +++ b/arch/x86/kvm/mmu/page_track.c
> @@ -229,7 +229,8 @@ void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
> return;
>
> idx = srcu_read_lock(&head->track_srcu);
> - hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> + hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
> + srcu_read_lock_held(&head->track_srcu))
> if (n->track_write)
> n->track_write(vcpu, gpa, new, bytes, n);
> srcu_read_unlock(&head->track_srcu, idx);
> @@ -254,7 +255,8 @@ void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
> return;
>
> idx = srcu_read_lock(&head->track_srcu);
> - hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> + hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
> + srcu_read_lock_held(&head->track_srcu))
> if (n->track_flush_slot)
> n->track_flush_slot(kvm, slot, n);
> srcu_read_unlock(&head->track_srcu, idx);
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH] kvm: Fix false positive RCU usage warning
@ 2020-04-29 20:20 ` Qian Cai
0 siblings, 0 replies; 6+ messages in thread
From: Qian Cai @ 2020-04-29 20:20 UTC (permalink / raw)
To: Madhuparna Bhowmik
Cc: wanpengli, kvm, paul E. McKenney, x86, LKML, Sean Christopherson,
Ingo Molnar, Borislav Petkov, Joel Fernandes (Google),
Paolo Bonzini, Thomas Gleixner, linux-kernel-mentees, jmattson
> On Apr 28, 2020, at 11:52 AM, madhuparnabhowmik10@gmail.com wrote:
>
> From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
>
> Fix the following false positive warnings:
>
> [ 9403.765413][T61744] =============================
> [ 9403.786541][T61744] WARNING: suspicious RCU usage
> [ 9403.807865][T61744] 5.7.0-rc1-next-20200417 #4 Tainted: G L
> [ 9403.838945][T61744] -----------------------------
> [ 9403.860099][T61744] arch/x86/kvm/mmu/page_track.c:257 RCU-list traversed in non-reader section!!
>
> and
>
> [ 9405.859252][T61751] =============================
> [ 9405.859258][T61751] WARNING: suspicious RCU usage
> [ 9405.880867][T61755] -----------------------------
> [ 9405.911936][T61751] 5.7.0-rc1-next-20200417 #4 Tainted: G L
> [ 9405.911942][T61751] -----------------------------
> [ 9405.911950][T61751] arch/x86/kvm/mmu/page_track.c:232 RCU-list traversed in non-reader section!!
>
> Since srcu read lock is held, these are false positive warnings.
> Therefore, pass condition srcu_read_lock_held() to
> list_for_each_entry_rcu().
You forgot to add KVM maintainer (adding Paolo now). On the other hand, there could be more places need to audit in x86 KVM. Not sure you want to add them together to one patch or doing separately for each file. For example,
[29179.937976][T75781] WARNING: suspicious RCU usage
[29179.942789][T75781] 5.7.0-rc3-next-20200429 #1 Tainted: G O L
[29179.949752][T75781] -----------------------------
[29179.954498][T75781] arch/x86/kvm/../../../virt/kvm/eventfd.c:472 RCU-list traversed in non-reader section!!
[29179.964768][T75781]
[29179.964768][T75781] other info that might help us debug this:
[29179.964768][T75781]
[29179.974958][T75781]
[29179.974958][T75781] rcu_scheduler_active = 2, debug_locks = 1
[29179.982961][T75781] 3 locks held by qemu-kvm/75781:
[29179.988145][T75781] #0: ffff95b3755300d0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0xbd/0x860 [kvm]
[29179.998450][T75781] #1: ffffa45946cd7e10 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x94e/0x2e50 [kvm]
[29180.009264][T75781] #2: ffffa45946cd8b98 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x92/0x290 [kvm]
[29180.020471][T75781]
[29180.020471][T75781] stack backtrace:
[29180.026318][T75781] CPU: 16 PID: 75781 Comm: qemu-kvm Tainted: G O L 5.7.0-rc3-next-20200429 #1
[29180.036480][T75781] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 03/09/2018
[29180.045765][T75781] Call Trace:
[29180.048942][T75781] dump_stack+0xab/0x100
[29180.053132][T75781] lockdep_rcu_suspicious+0xea/0xf3
[29180.058802][T75781] kvm_notify_acked_gsi+0x10d/0x120 [kvm]
[29180.065386][T75781] kvm_notify_acked_irq+0xe5/0x290 [kvm]
[29180.071529][T75781] pic_clear_isr+0xa1/0xc0 [kvm]
[29180.077118][T75781] pic_ioport_write+0x335/0x5e0 [kvm]
[29180.082453][T75781] ? do_raw_spin_lock+0x115/0x1b0
[29180.088205][T75781] picdev_write+0x7d/0x130 [kvm]
[29180.093677][T75781] picdev_master_write+0x3a/0x50 [kvm]
[29180.099730][T75781] __kvm_io_bus_write+0x147/0x180 [kvm]
[29180.105700][T75781] kvm_io_bus_write+0xfc/0x1b0 [kvm]
[29180.111701][T75781] kernel_pio+0xeb/0x110 [kvm]
[29180.116991][T75781] emulator_pio_out+0x14f/0x400 [kvm]
[29180.122342][T75781] ? __lock_acquire+0x5c2/0x23f0
[29180.127229][T75781] ? __svm_vcpu_run+0x95/0x110 [kvm_amd]
[29180.133481][T75781] kvm_fast_pio+0x12f/0x200 [kvm]
[29180.138733][T75781] io_interception+0xba/0xe0 [kvm_amd]
[29180.144164][T75781] ? svm_sync_dirty_debug_regs+0x170/0x170 [kvm_amd]
[29180.150843][T75781] handle_exit+0x403/0x9f0 [kvm_amd]
[29180.156652][T75781] ? kvm_arch_vcpu_ioctl_run+0x286/0xb50 [kvm]
[29180.163648][T75781] vcpu_enter_guest+0xa08/0x2e50 [kvm]
[29180.169007][T75781] ? lock_acquire+0xcd/0x450
[29180.174364][T75781] ? kvm_skip_emulated_instruction+0x67/0x80 [kvm]
[29180.181422][T75781] kvm_arch_vcpu_ioctl_run+0x286/0xb50 [kvm]
[29180.188256][T75781] kvm_vcpu_ioctl+0x2d4/0x860 [kvm]
[29180.193391][T75781] ? __fget_light+0xa3/0x170
[29180.197879][T75781] ksys_ioctl+0x227/0xb90
[29180.202159][T75781] ? find_held_lock+0x35/0xa0
[29180.206777][T75781] __x64_sys_ioctl+0x4c/0x5d
[29180.211443][T75781] do_syscall_64+0x91/0xb10
[29180.215840][T75781] ? trace_hardirqs_off_thunk+0x1a/0x1c
[29180.221307][T75781] entry_SYSCALL_64_after_hwframe+0x49/0xb3
[29180.227100][T75781] RIP: 0033:0x7f2f5a90487b
[29180.231414][T75781] Code: 0f 1e fa 48 8b 05 0d 96 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d dd 95 2c 00 f7 d8 64 89 01 48
[29180.251241][T75781] RSP: 002b:00007f2f4b7fd678 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[29180.259660][T75781] RAX: ffffffffffffffda RBX: 00007f2f5fc31001 RCX: 00007f2f5a90487b
[29180.267730][T75781] RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000011
[29180.275619][T75781] RBP: 0000000000000001 R08: 000055c707b6fad0 R09: 00000000000000ff
[29180.283533][T75781] R10: 0000000000000001 R11: 0000000000000246 R12: 000055c707b58100
[29180.291622][T75781] R13: 0000000000000000 R14: 00007f2f5fc30000 R15: 000055c70a1b4c60
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
> ---
> arch/x86/kvm/mmu/page_track.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
> index ddc1ec3bdacd..1ad79c7aa05b 100644
> --- a/arch/x86/kvm/mmu/page_track.c
> +++ b/arch/x86/kvm/mmu/page_track.c
> @@ -229,7 +229,8 @@ void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
> return;
>
> idx = srcu_read_lock(&head->track_srcu);
> - hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> + hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
> + srcu_read_lock_held(&head->track_srcu))
> if (n->track_write)
> n->track_write(vcpu, gpa, new, bytes, n);
> srcu_read_unlock(&head->track_srcu, idx);
> @@ -254,7 +255,8 @@ void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
> return;
>
> idx = srcu_read_lock(&head->track_srcu);
> - hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> + hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
> + srcu_read_lock_held(&head->track_srcu))
> if (n->track_flush_slot)
> n->track_flush_slot(kvm, slot, n);
> srcu_read_unlock(&head->track_srcu, idx);
> --
> 2.17.1
>
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] kvm: Fix false positive RCU usage warning
2020-04-29 20:20 ` [Linux-kernel-mentees] " Qian Cai
@ 2020-04-30 16:21 ` Madhuparna Bhowmik
-1 siblings, 0 replies; 6+ messages in thread
From: Madhuparna Bhowmik @ 2020-04-30 16:21 UTC (permalink / raw)
To: Qian Cai
Cc: Madhuparna Bhowmik, Sean Christopherson, wanpengli, jmattson,
Thomas Gleixner, Borislav Petkov, Ingo Molnar, paul E. McKenney,
Joel Fernandes (Google),
Amol Grover, x86, kvm, linux-kernel-mentees, LKML, Paolo Bonzini
On Wed, Apr 29, 2020 at 04:20:29PM -0400, Qian Cai wrote:
>
>
> > On Apr 28, 2020, at 11:52 AM, madhuparnabhowmik10@gmail.com wrote:
> >
> > From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
> >
> > Fix the following false positive warnings:
> >
> > [ 9403.765413][T61744] =============================
> > [ 9403.786541][T61744] WARNING: suspicious RCU usage
> > [ 9403.807865][T61744] 5.7.0-rc1-next-20200417 #4 Tainted: G L
> > [ 9403.838945][T61744] -----------------------------
> > [ 9403.860099][T61744] arch/x86/kvm/mmu/page_track.c:257 RCU-list traversed in non-reader section!!
> >
> > and
> >
> > [ 9405.859252][T61751] =============================
> > [ 9405.859258][T61751] WARNING: suspicious RCU usage
> > [ 9405.880867][T61755] -----------------------------
> > [ 9405.911936][T61751] 5.7.0-rc1-next-20200417 #4 Tainted: G L
> > [ 9405.911942][T61751] -----------------------------
> > [ 9405.911950][T61751] arch/x86/kvm/mmu/page_track.c:232 RCU-list traversed in non-reader section!!
> >
> > Since srcu read lock is held, these are false positive warnings.
> > Therefore, pass condition srcu_read_lock_held() to
> > list_for_each_entry_rcu().
>
> You forgot to add KVM maintainer (adding Paolo now). On the other hand, there could be more places need to audit in x86 KVM. Not sure you want to add them together to one patch or doing separately for each file. For example,
>
Thank you for adding him.
I am looking into these other warnings.
I will send a seperate patch for them.
Regards,
Madhuparna
> [29179.937976][T75781] WARNING: suspicious RCU usage
> [29179.942789][T75781] 5.7.0-rc3-next-20200429 #1 Tainted: G O L
> [29179.949752][T75781] -----------------------------
> [29179.954498][T75781] arch/x86/kvm/../../../virt/kvm/eventfd.c:472 RCU-list traversed in non-reader section!!
> [29179.964768][T75781]
> [29179.964768][T75781] other info that might help us debug this:
> [29179.964768][T75781]
> [29179.974958][T75781]
> [29179.974958][T75781] rcu_scheduler_active = 2, debug_locks = 1
> [29179.982961][T75781] 3 locks held by qemu-kvm/75781:
> [29179.988145][T75781] #0: ffff95b3755300d0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0xbd/0x860 [kvm]
> [29179.998450][T75781] #1: ffffa45946cd7e10 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x94e/0x2e50 [kvm]
> [29180.009264][T75781] #2: ffffa45946cd8b98 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x92/0x290 [kvm]
> [29180.020471][T75781]
> [29180.020471][T75781] stack backtrace:
> [29180.026318][T75781] CPU: 16 PID: 75781 Comm: qemu-kvm Tainted: G O L 5.7.0-rc3-next-20200429 #1
> [29180.036480][T75781] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 03/09/2018
> [29180.045765][T75781] Call Trace:
> [29180.048942][T75781] dump_stack+0xab/0x100
> [29180.053132][T75781] lockdep_rcu_suspicious+0xea/0xf3
> [29180.058802][T75781] kvm_notify_acked_gsi+0x10d/0x120 [kvm]
> [29180.065386][T75781] kvm_notify_acked_irq+0xe5/0x290 [kvm]
> [29180.071529][T75781] pic_clear_isr+0xa1/0xc0 [kvm]
> [29180.077118][T75781] pic_ioport_write+0x335/0x5e0 [kvm]
> [29180.082453][T75781] ? do_raw_spin_lock+0x115/0x1b0
> [29180.088205][T75781] picdev_write+0x7d/0x130 [kvm]
> [29180.093677][T75781] picdev_master_write+0x3a/0x50 [kvm]
> [29180.099730][T75781] __kvm_io_bus_write+0x147/0x180 [kvm]
> [29180.105700][T75781] kvm_io_bus_write+0xfc/0x1b0 [kvm]
> [29180.111701][T75781] kernel_pio+0xeb/0x110 [kvm]
> [29180.116991][T75781] emulator_pio_out+0x14f/0x400 [kvm]
> [29180.122342][T75781] ? __lock_acquire+0x5c2/0x23f0
> [29180.127229][T75781] ? __svm_vcpu_run+0x95/0x110 [kvm_amd]
> [29180.133481][T75781] kvm_fast_pio+0x12f/0x200 [kvm]
> [29180.138733][T75781] io_interception+0xba/0xe0 [kvm_amd]
> [29180.144164][T75781] ? svm_sync_dirty_debug_regs+0x170/0x170 [kvm_amd]
> [29180.150843][T75781] handle_exit+0x403/0x9f0 [kvm_amd]
> [29180.156652][T75781] ? kvm_arch_vcpu_ioctl_run+0x286/0xb50 [kvm]
> [29180.163648][T75781] vcpu_enter_guest+0xa08/0x2e50 [kvm]
> [29180.169007][T75781] ? lock_acquire+0xcd/0x450
> [29180.174364][T75781] ? kvm_skip_emulated_instruction+0x67/0x80 [kvm]
> [29180.181422][T75781] kvm_arch_vcpu_ioctl_run+0x286/0xb50 [kvm]
> [29180.188256][T75781] kvm_vcpu_ioctl+0x2d4/0x860 [kvm]
> [29180.193391][T75781] ? __fget_light+0xa3/0x170
> [29180.197879][T75781] ksys_ioctl+0x227/0xb90
> [29180.202159][T75781] ? find_held_lock+0x35/0xa0
> [29180.206777][T75781] __x64_sys_ioctl+0x4c/0x5d
> [29180.211443][T75781] do_syscall_64+0x91/0xb10
> [29180.215840][T75781] ? trace_hardirqs_off_thunk+0x1a/0x1c
> [29180.221307][T75781] entry_SYSCALL_64_after_hwframe+0x49/0xb3
> [29180.227100][T75781] RIP: 0033:0x7f2f5a90487b
> [29180.231414][T75781] Code: 0f 1e fa 48 8b 05 0d 96 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d dd 95 2c 00 f7 d8 64 89 01 48
> [29180.251241][T75781] RSP: 002b:00007f2f4b7fd678 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> [29180.259660][T75781] RAX: ffffffffffffffda RBX: 00007f2f5fc31001 RCX: 00007f2f5a90487b
> [29180.267730][T75781] RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000011
> [29180.275619][T75781] RBP: 0000000000000001 R08: 000055c707b6fad0 R09: 00000000000000ff
> [29180.283533][T75781] R10: 0000000000000001 R11: 0000000000000246 R12: 000055c707b58100
> [29180.291622][T75781] R13: 0000000000000000 R14: 00007f2f5fc30000 R15: 000055c70a1b4c60
>
> >
> > Reported-by: kernel test robot <lkp@intel.com>
> > Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
> > ---
> > arch/x86/kvm/mmu/page_track.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
> > index ddc1ec3bdacd..1ad79c7aa05b 100644
> > --- a/arch/x86/kvm/mmu/page_track.c
> > +++ b/arch/x86/kvm/mmu/page_track.c
> > @@ -229,7 +229,8 @@ void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
> > return;
> >
> > idx = srcu_read_lock(&head->track_srcu);
> > - hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> > + hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
> > + srcu_read_lock_held(&head->track_srcu))
> > if (n->track_write)
> > n->track_write(vcpu, gpa, new, bytes, n);
> > srcu_read_unlock(&head->track_srcu, idx);
> > @@ -254,7 +255,8 @@ void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
> > return;
> >
> > idx = srcu_read_lock(&head->track_srcu);
> > - hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> > + hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
> > + srcu_read_lock_held(&head->track_srcu))
> > if (n->track_flush_slot)
> > n->track_flush_slot(kvm, slot, n);
> > srcu_read_unlock(&head->track_srcu, idx);
> > --
> > 2.17.1
> >
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH] kvm: Fix false positive RCU usage warning
@ 2020-04-30 16:21 ` Madhuparna Bhowmik
0 siblings, 0 replies; 6+ messages in thread
From: Madhuparna Bhowmik @ 2020-04-30 16:21 UTC (permalink / raw)
To: Qian Cai
Cc: wanpengli, kvm, paul E. McKenney, x86, LKML, Sean Christopherson,
Madhuparna Bhowmik, Ingo Molnar, Borislav Petkov,
Joel Fernandes (Google),
Paolo Bonzini, Thomas Gleixner, linux-kernel-mentees, jmattson
On Wed, Apr 29, 2020 at 04:20:29PM -0400, Qian Cai wrote:
>
>
> > On Apr 28, 2020, at 11:52 AM, madhuparnabhowmik10@gmail.com wrote:
> >
> > From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
> >
> > Fix the following false positive warnings:
> >
> > [ 9403.765413][T61744] =============================
> > [ 9403.786541][T61744] WARNING: suspicious RCU usage
> > [ 9403.807865][T61744] 5.7.0-rc1-next-20200417 #4 Tainted: G L
> > [ 9403.838945][T61744] -----------------------------
> > [ 9403.860099][T61744] arch/x86/kvm/mmu/page_track.c:257 RCU-list traversed in non-reader section!!
> >
> > and
> >
> > [ 9405.859252][T61751] =============================
> > [ 9405.859258][T61751] WARNING: suspicious RCU usage
> > [ 9405.880867][T61755] -----------------------------
> > [ 9405.911936][T61751] 5.7.0-rc1-next-20200417 #4 Tainted: G L
> > [ 9405.911942][T61751] -----------------------------
> > [ 9405.911950][T61751] arch/x86/kvm/mmu/page_track.c:232 RCU-list traversed in non-reader section!!
> >
> > Since srcu read lock is held, these are false positive warnings.
> > Therefore, pass condition srcu_read_lock_held() to
> > list_for_each_entry_rcu().
>
> You forgot to add KVM maintainer (adding Paolo now). On the other hand, there could be more places need to audit in x86 KVM. Not sure you want to add them together to one patch or doing separately for each file. For example,
>
Thank you for adding him.
I am looking into these other warnings.
I will send a seperate patch for them.
Regards,
Madhuparna
> [29179.937976][T75781] WARNING: suspicious RCU usage
> [29179.942789][T75781] 5.7.0-rc3-next-20200429 #1 Tainted: G O L
> [29179.949752][T75781] -----------------------------
> [29179.954498][T75781] arch/x86/kvm/../../../virt/kvm/eventfd.c:472 RCU-list traversed in non-reader section!!
> [29179.964768][T75781]
> [29179.964768][T75781] other info that might help us debug this:
> [29179.964768][T75781]
> [29179.974958][T75781]
> [29179.974958][T75781] rcu_scheduler_active = 2, debug_locks = 1
> [29179.982961][T75781] 3 locks held by qemu-kvm/75781:
> [29179.988145][T75781] #0: ffff95b3755300d0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0xbd/0x860 [kvm]
> [29179.998450][T75781] #1: ffffa45946cd7e10 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x94e/0x2e50 [kvm]
> [29180.009264][T75781] #2: ffffa45946cd8b98 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x92/0x290 [kvm]
> [29180.020471][T75781]
> [29180.020471][T75781] stack backtrace:
> [29180.026318][T75781] CPU: 16 PID: 75781 Comm: qemu-kvm Tainted: G O L 5.7.0-rc3-next-20200429 #1
> [29180.036480][T75781] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 03/09/2018
> [29180.045765][T75781] Call Trace:
> [29180.048942][T75781] dump_stack+0xab/0x100
> [29180.053132][T75781] lockdep_rcu_suspicious+0xea/0xf3
> [29180.058802][T75781] kvm_notify_acked_gsi+0x10d/0x120 [kvm]
> [29180.065386][T75781] kvm_notify_acked_irq+0xe5/0x290 [kvm]
> [29180.071529][T75781] pic_clear_isr+0xa1/0xc0 [kvm]
> [29180.077118][T75781] pic_ioport_write+0x335/0x5e0 [kvm]
> [29180.082453][T75781] ? do_raw_spin_lock+0x115/0x1b0
> [29180.088205][T75781] picdev_write+0x7d/0x130 [kvm]
> [29180.093677][T75781] picdev_master_write+0x3a/0x50 [kvm]
> [29180.099730][T75781] __kvm_io_bus_write+0x147/0x180 [kvm]
> [29180.105700][T75781] kvm_io_bus_write+0xfc/0x1b0 [kvm]
> [29180.111701][T75781] kernel_pio+0xeb/0x110 [kvm]
> [29180.116991][T75781] emulator_pio_out+0x14f/0x400 [kvm]
> [29180.122342][T75781] ? __lock_acquire+0x5c2/0x23f0
> [29180.127229][T75781] ? __svm_vcpu_run+0x95/0x110 [kvm_amd]
> [29180.133481][T75781] kvm_fast_pio+0x12f/0x200 [kvm]
> [29180.138733][T75781] io_interception+0xba/0xe0 [kvm_amd]
> [29180.144164][T75781] ? svm_sync_dirty_debug_regs+0x170/0x170 [kvm_amd]
> [29180.150843][T75781] handle_exit+0x403/0x9f0 [kvm_amd]
> [29180.156652][T75781] ? kvm_arch_vcpu_ioctl_run+0x286/0xb50 [kvm]
> [29180.163648][T75781] vcpu_enter_guest+0xa08/0x2e50 [kvm]
> [29180.169007][T75781] ? lock_acquire+0xcd/0x450
> [29180.174364][T75781] ? kvm_skip_emulated_instruction+0x67/0x80 [kvm]
> [29180.181422][T75781] kvm_arch_vcpu_ioctl_run+0x286/0xb50 [kvm]
> [29180.188256][T75781] kvm_vcpu_ioctl+0x2d4/0x860 [kvm]
> [29180.193391][T75781] ? __fget_light+0xa3/0x170
> [29180.197879][T75781] ksys_ioctl+0x227/0xb90
> [29180.202159][T75781] ? find_held_lock+0x35/0xa0
> [29180.206777][T75781] __x64_sys_ioctl+0x4c/0x5d
> [29180.211443][T75781] do_syscall_64+0x91/0xb10
> [29180.215840][T75781] ? trace_hardirqs_off_thunk+0x1a/0x1c
> [29180.221307][T75781] entry_SYSCALL_64_after_hwframe+0x49/0xb3
> [29180.227100][T75781] RIP: 0033:0x7f2f5a90487b
> [29180.231414][T75781] Code: 0f 1e fa 48 8b 05 0d 96 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d dd 95 2c 00 f7 d8 64 89 01 48
> [29180.251241][T75781] RSP: 002b:00007f2f4b7fd678 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> [29180.259660][T75781] RAX: ffffffffffffffda RBX: 00007f2f5fc31001 RCX: 00007f2f5a90487b
> [29180.267730][T75781] RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000011
> [29180.275619][T75781] RBP: 0000000000000001 R08: 000055c707b6fad0 R09: 00000000000000ff
> [29180.283533][T75781] R10: 0000000000000001 R11: 0000000000000246 R12: 000055c707b58100
> [29180.291622][T75781] R13: 0000000000000000 R14: 00007f2f5fc30000 R15: 000055c70a1b4c60
>
> >
> > Reported-by: kernel test robot <lkp@intel.com>
> > Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
> > ---
> > arch/x86/kvm/mmu/page_track.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
> > index ddc1ec3bdacd..1ad79c7aa05b 100644
> > --- a/arch/x86/kvm/mmu/page_track.c
> > +++ b/arch/x86/kvm/mmu/page_track.c
> > @@ -229,7 +229,8 @@ void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
> > return;
> >
> > idx = srcu_read_lock(&head->track_srcu);
> > - hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> > + hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
> > + srcu_read_lock_held(&head->track_srcu))
> > if (n->track_write)
> > n->track_write(vcpu, gpa, new, bytes, n);
> > srcu_read_unlock(&head->track_srcu, idx);
> > @@ -254,7 +255,8 @@ void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
> > return;
> >
> > idx = srcu_read_lock(&head->track_srcu);
> > - hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> > + hlist_for_each_entry_rcu(n, &head->track_notifier_list, node,
> > + srcu_read_lock_held(&head->track_srcu))
> > if (n->track_flush_slot)
> > n->track_flush_slot(kvm, slot, n);
> > srcu_read_unlock(&head->track_srcu, idx);
> > --
> > 2.17.1
> >
>
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-04-30 16:21 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-04-28 15:52 [PATCH] kvm: Fix false positive RCU usage warning madhuparnabhowmik10
2020-04-28 15:52 ` [Linux-kernel-mentees] " madhuparnabhowmik10
2020-04-29 20:20 ` Qian Cai
2020-04-29 20:20 ` [Linux-kernel-mentees] " Qian Cai
2020-04-30 16:21 ` Madhuparna Bhowmik
2020-04-30 16:21 ` [Linux-kernel-mentees] " Madhuparna Bhowmik
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