On Wed, Apr 29, 2020 at 04:20:29PM -0400, Qian Cai wrote:
>
>
> > On Apr 28, 2020, at 11:52 AM, [email protected] wrote:
> >
> > From: Madhuparna Bhowmik <[email protected]>
> >
> > 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 <[email protected]>
> > Signed-off-by: Madhuparna Bhowmik <[email protected]>
> > ---
> > 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
> >
>
