From 62d02fd1f807bf5a259a242c483c9fb98a242630 Mon Sep 17 00:00:00 2001 From: Chuanxiao Dong Date: Mon, 26 Jun 2017 15:20:49 +0800 Subject: [PATCH] drm/i915/gvt: Fix possible recursive locking issue vfio_unpin_pages will hold a read semaphore however it is already hold in the same thread by vfio ioctl. It will cause below warning: [ 5102.127454] ============================================ [ 5102.133379] WARNING: possible recursive locking detected [ 5102.139304] 4.12.0-rc4+ #3 Not tainted [ 5102.143483] -------------------------------------------- [ 5102.149407] qemu-system-x86/1620 is trying to acquire lock: [ 5102.155624] (&container->group_lock){++++++}, at: [] vfio_unpin_pages+0x96/0xf0 [ 5102.165626] but task is already holding lock: [ 5102.172134] (&container->group_lock){++++++}, at: [] vfio_fops_unl_ioctl+0x5f/0x280 [ 5102.182522] other info that might help us debug this: [ 5102.189806] Possible unsafe locking scenario: [ 5102.196411] CPU0 [ 5102.199136] ---- [ 5102.201861] lock(&container->group_lock); [ 5102.206527] lock(&container->group_lock); [ 5102.211191] *** DEADLOCK *** [ 5102.217796] May be due to missing lock nesting notation [ 5102.225370] 3 locks held by qemu-system-x86/1620: [ 5102.230618] #0: (&container->group_lock){++++++}, at: [] vfio_fops_unl_ioctl+0x5f/0x280 [ 5102.241482] #1: (&(&iommu->notifier)->rwsem){++++..}, at: [] __blocking_notifier_call_chain+0x35/0x70 [ 5102.253713] #2: (&vgpu->vdev.cache_lock){+.+...}, at: [] intel_vgpu_iommu_notifier+0x77/0x120 [ 5102.265163] stack backtrace: [ 5102.270022] CPU: 5 PID: 1620 Comm: qemu-system-x86 Not tainted 4.12.0-rc4+ #3 [ 5102.277991] Hardware name: Intel Corporation S1200RP/S1200RP, BIOS S1200RP.86B.03.01.APER.061220151418 06/12/2015 [ 5102.289445] Call Trace: [ 5102.292175] dump_stack+0x85/0xc7 [ 5102.295871] validate_chain.isra.21+0x9da/0xaf0 [ 5102.300925] __lock_acquire+0x405/0x820 [ 5102.305202] lock_acquire+0xc7/0x220 [ 5102.309191] ? vfio_unpin_pages+0x96/0xf0 [ 5102.313666] down_read+0x2b/0x50 [ 5102.317259] ? vfio_unpin_pages+0x96/0xf0 [ 5102.321732] vfio_unpin_pages+0x96/0xf0 [ 5102.326024] intel_vgpu_iommu_notifier+0xe5/0x120 [ 5102.331283] notifier_call_chain+0x4a/0x70 [ 5102.335851] __blocking_notifier_call_chain+0x4d/0x70 [ 5102.341490] blocking_notifier_call_chain+0x16/0x20 [ 5102.346935] vfio_iommu_type1_ioctl+0x87b/0x920 [ 5102.351994] vfio_fops_unl_ioctl+0x81/0x280 [ 5102.356660] ? __fget+0xf0/0x210 [ 5102.360261] do_vfs_ioctl+0x93/0x6a0 [ 5102.364247] ? __fget+0x111/0x210 [ 5102.367942] SyS_ioctl+0x41/0x70 [ 5102.371542] entry_SYSCALL_64_fastpath+0x1f/0xbe put the vfio_unpin_pages in a workqueue can fix this. v2: - use for style instead of do{}while(1). (Zhenyu) v3: - rename gvt_cache_mark to gvt_cache_mark_remove. (Zhenyu) Fixes: 659643f7d814 ("drm/i915/gvt/kvmgt: add vfio/mdev support to KVMGT") Signed-off-by: Chuanxiao Dong Cc: Zhenyu Wang Cc: stable@vger.kernel.org # v4.10+ Signed-off-by: Zhenyu Wang --- drivers/gpu/drm/i915/gvt/gvt.h | 3 ++ drivers/gpu/drm/i915/gvt/kvmgt.c | 55 ++++++++++++++++++++++++++------ 2 files changed, 48 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/i915/gvt/gvt.h b/drivers/gpu/drm/i915/gvt/gvt.h index 930732e5c780..8b5876d63624 100644 --- a/drivers/gpu/drm/i915/gvt/gvt.h +++ b/drivers/gpu/drm/i915/gvt/gvt.h @@ -183,6 +183,9 @@ struct intel_vgpu { struct kvm *kvm; struct work_struct release_work; atomic_t released; + struct work_struct unpin_work; + spinlock_t unpin_lock; /* To protect unpin_list */ + struct list_head unpin_list; } vdev; #endif }; diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c index 1ae0b4083ce1..56a8d6a7d9c6 100644 --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -78,6 +78,7 @@ struct gvt_dma { struct rb_node node; gfn_t gfn; unsigned long iova; + struct list_head list; }; static inline bool handle_valid(unsigned long handle) @@ -166,6 +167,7 @@ static void gvt_cache_add(struct intel_vgpu *vgpu, gfn_t gfn, new->gfn = gfn; new->iova = iova; + INIT_LIST_HEAD(&new->list); mutex_lock(&vgpu->vdev.cache_lock); while (*link) { @@ -197,26 +199,52 @@ static void __gvt_cache_remove_entry(struct intel_vgpu *vgpu, kfree(entry); } -static void gvt_cache_remove(struct intel_vgpu *vgpu, gfn_t gfn) +static void intel_vgpu_unpin_work(struct work_struct *work) { + struct intel_vgpu *vgpu = container_of(work, struct intel_vgpu, + vdev.unpin_work); struct device *dev = mdev_dev(vgpu->vdev.mdev); struct gvt_dma *this; - unsigned long g1; - int rc; + unsigned long gfn; + + for (;;) { + spin_lock(&vgpu->vdev.unpin_lock); + if (list_empty(&vgpu->vdev.unpin_list)) { + spin_unlock(&vgpu->vdev.unpin_lock); + break; + } + this = list_first_entry(&vgpu->vdev.unpin_list, + struct gvt_dma, list); + list_del(&this->list); + spin_unlock(&vgpu->vdev.unpin_lock); + + gfn = this->gfn; + vfio_unpin_pages(dev, &gfn, 1); + kfree(this); + } +} + +static bool gvt_cache_mark_remove(struct intel_vgpu *vgpu, gfn_t gfn) +{ + struct gvt_dma *this; mutex_lock(&vgpu->vdev.cache_lock); this = __gvt_cache_find(vgpu, gfn); if (!this) { mutex_unlock(&vgpu->vdev.cache_lock); - return; + return false; } - - g1 = gfn; gvt_dma_unmap_iova(vgpu, this->iova); - rc = vfio_unpin_pages(dev, &g1, 1); - WARN_ON(rc != 1); - __gvt_cache_remove_entry(vgpu, this); + /* remove this from rb tree */ + rb_erase(&this->node, &vgpu->vdev.cache); mutex_unlock(&vgpu->vdev.cache_lock); + + /* put this to the unpin_list */ + spin_lock(&vgpu->vdev.unpin_lock); + list_move_tail(&this->list, &vgpu->vdev.unpin_list); + spin_unlock(&vgpu->vdev.unpin_lock); + + return true; } static void gvt_cache_init(struct intel_vgpu *vgpu) @@ -453,6 +481,9 @@ static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev) } INIT_WORK(&vgpu->vdev.release_work, intel_vgpu_release_work); + INIT_WORK(&vgpu->vdev.unpin_work, intel_vgpu_unpin_work); + spin_lock_init(&vgpu->vdev.unpin_lock); + INIT_LIST_HEAD(&vgpu->vdev.unpin_list); vgpu->vdev.mdev = mdev; mdev_set_drvdata(mdev, vgpu); @@ -482,6 +513,7 @@ static int intel_vgpu_iommu_notifier(struct notifier_block *nb, struct intel_vgpu *vgpu = container_of(nb, struct intel_vgpu, vdev.iommu_notifier); + bool sched_unmap = false; if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) { struct vfio_iommu_type1_dma_unmap *unmap = data; @@ -491,7 +523,10 @@ static int intel_vgpu_iommu_notifier(struct notifier_block *nb, end_gfn = gfn + unmap->size / PAGE_SIZE; while (gfn < end_gfn) - gvt_cache_remove(vgpu, gfn++); + sched_unmap |= gvt_cache_mark_remove(vgpu, gfn++); + + if (sched_unmap) + schedule_work(&vgpu->vdev.unpin_work); } return NOTIFY_OK; -- 2.20.1