Message ID | 20190821215030.31660-1-daniel.vetter@ffwll.ch (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | [1/3] dma_resv: prime lockdep annotations | expand |
Quoting Daniel Vetter (2019-08-21 22:50:28) > Full audit of everyone: > > - i915, radeon, amdgpu should be clean per their maintainers. > > - vram helpers should be fine, they don't do command submission, so > really no business holding struct_mutex while doing copy_*_user. But > I haven't checked them all. > > - panfrost seems to dma_resv_lock only in panfrost_job_push, which > looks clean. > > - v3d holds dma_resv locks in the tail of its v3d_submit_cl_ioctl(), > copying from/to userspace happens all in v3d_lookup_bos which is > outside of the critical section. > > - vmwgfx has a bunch of ioctls that do their own copy_*_user: > - vmw_execbuf_process: First this does some copies in > vmw_execbuf_cmdbuf() and also in the vmw_execbuf_process() itself. > Then comes the usual ttm reserve/validate sequence, then actual > submission/fencing, then unreserving, and finally some more > copy_to_user in vmw_execbuf_copy_fence_user. Glossing over tons of > details, but looks all safe. > - vmw_fence_event_ioctl: No ttm_reserve/dma_resv_lock anywhere to be > seen, seems to only create a fence and copy it out. > - a pile of smaller ioctl in vmwgfx_ioctl.c, no reservations to be > found there. > Summary: vmwgfx seems to be fine too. > > - virtio: There's virtio_gpu_execbuffer_ioctl, which does all the > copying from userspace before even looking up objects through their > handles, so safe. Plus the getparam/getcaps ioctl, also both safe. > > - qxl only has qxl_execbuffer_ioctl, which calls into > qxl_process_single_command. There's a lovely comment before the > __copy_from_user_inatomic that the slowpath should be copied from > i915, but I guess that never happened. Try not to be unlucky and get > your CS data evicted between when it's written and the kernel tries > to read it. The only other copy_from_user is for relocs, but those > are done before qxl_release_reserve_list(), which seems to be the > only thing reserving buffers (in the ttm/dma_resv sense) in that > code. So looks safe. > > - A debugfs file in nouveau_debugfs_pstate_set() and the usif ioctl in > usif_ioctl() look safe. nouveau_gem_ioctl_pushbuf() otoh breaks this > everywhere and needs to be fixed up. > > v2: Thomas pointed at that vmwgfx calls dma_resv_init while it holds a > dma_resv lock of a different object already. Christian mentioned that > ttm core does this too for ghost objects. intel-gfx-ci highlighted > that i915 has similar issues. > > Unfortunately we can't do this in the usual module init functions, > because kernel threads don't have an ->mm - we have to wait around for > some user thread to do this. > > Solution is to spawn a worker (but only once). It's horrible, but it > works. > > Cc: Alex Deucher <alexander.deucher@amd.com> > Cc: Christian König <christian.koenig@amd.com> > Cc: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Thomas Zimmermann <tzimmermann@suse.de> > Cc: Rob Herring <robh@kernel.org> > Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com> > Cc: Eric Anholt <eric@anholt.net> > Cc: Dave Airlie <airlied@redhat.com> > Cc: Gerd Hoffmann <kraxel@redhat.com> > Cc: Ben Skeggs <bskeggs@redhat.com> > Cc: "VMware Graphics" <linux-graphics-maintainer@vmware.com> > Cc: Thomas Hellstrom <thellstrom@vmware.com> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> > --- > drivers/dma-buf/dma-resv.c | 42 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c > index 42a8f3f11681..29988b1564c1 100644 > --- a/drivers/dma-buf/dma-resv.c > +++ b/drivers/dma-buf/dma-resv.c > @@ -34,6 +34,7 @@ > > #include <linux/dma-resv.h> > #include <linux/export.h> > +#include <linux/sched/mm.h> > > /** > * DOC: Reservation Object Overview > @@ -95,6 +96,28 @@ static void dma_resv_list_free(struct dma_resv_list *list) > kfree_rcu(list, rcu); > } > > +#if IS_ENABLED(CONFIG_LOCKDEP) > +struct lockdep_work { > + struct work_struct work; > + struct dma_resv obj; > + struct mm_struct *mm; > +} lockdep_work; > + > +void lockdep_work_fn(struct work_struct *work) > +{ > + dma_resv_init(&lockdep_work.obj); > + > + down_read(&lockdep_work.mm->mmap_sem); > + ww_mutex_lock(&lockdep_work.obj.lock, NULL); > + fs_reclaim_acquire(GFP_KERNEL); > + fs_reclaim_release(GFP_KERNEL); > + ww_mutex_unlock(&lockdep_work.obj.lock); > + up_read(&lockdep_work.mm->mmap_sem); > + > + mmput(lockdep_work.mm); > +} > +#endif #if IS_ENABLED(CONFIG_LOCKDEP) static void dma_resv_lockmap(void) { struct mm_struct *mm = alloc_mm(); struct dma_resv obj; dma_resv_init(&obj); down_read(&mm->mmap_sem); ww_mutex_lock(&obj.lock, NULL); fs_reclaim_acquire(GFP_KERNEL); fs_reclaim_release(GFP_KERNEL); ww_mutex_unlock(&obj.lock); up_read(&mm->mmap_sem); mmput(mm); } core_initcall(dma_resv_lockmap); #endif as a thought. -Chris
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index 42a8f3f11681..29988b1564c1 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -34,6 +34,7 @@ #include <linux/dma-resv.h> #include <linux/export.h> +#include <linux/sched/mm.h> /** * DOC: Reservation Object Overview @@ -95,6 +96,28 @@ static void dma_resv_list_free(struct dma_resv_list *list) kfree_rcu(list, rcu); } +#if IS_ENABLED(CONFIG_LOCKDEP) +struct lockdep_work { + struct work_struct work; + struct dma_resv obj; + struct mm_struct *mm; +} lockdep_work; + +void lockdep_work_fn(struct work_struct *work) +{ + dma_resv_init(&lockdep_work.obj); + + down_read(&lockdep_work.mm->mmap_sem); + ww_mutex_lock(&lockdep_work.obj.lock, NULL); + fs_reclaim_acquire(GFP_KERNEL); + fs_reclaim_release(GFP_KERNEL); + ww_mutex_unlock(&lockdep_work.obj.lock); + up_read(&lockdep_work.mm->mmap_sem); + + mmput(lockdep_work.mm); +} +#endif + /** * dma_resv_init - initialize a reservation object * @obj: the reservation object @@ -107,6 +130,25 @@ void dma_resv_init(struct dma_resv *obj) &reservation_seqcount_class); RCU_INIT_POINTER(obj->fence, NULL); RCU_INIT_POINTER(obj->fence_excl, NULL); + +#if IS_ENABLED(CONFIG_LOCKDEP) + if (current->mm) { + static atomic_t lockdep_primed; + + /* + * This gets called from all kinds of places, launch a worker. + * Usual init sections don't work for kernel threads lack an + * ->mm. + */ + if (atomic_cmpxchg(&lockdep_primed, 0, 1) == 0) { + INIT_WORK(&lockdep_work.work, lockdep_work_fn); + lockdep_work.mm = current->mm; + mmget(lockdep_work.mm); + + schedule_work(&lockdep_work.work); + } + } +#endif } EXPORT_SYMBOL(dma_resv_init);
Full audit of everyone: - i915, radeon, amdgpu should be clean per their maintainers. - vram helpers should be fine, they don't do command submission, so really no business holding struct_mutex while doing copy_*_user. But I haven't checked them all. - panfrost seems to dma_resv_lock only in panfrost_job_push, which looks clean. - v3d holds dma_resv locks in the tail of its v3d_submit_cl_ioctl(), copying from/to userspace happens all in v3d_lookup_bos which is outside of the critical section. - vmwgfx has a bunch of ioctls that do their own copy_*_user: - vmw_execbuf_process: First this does some copies in vmw_execbuf_cmdbuf() and also in the vmw_execbuf_process() itself. Then comes the usual ttm reserve/validate sequence, then actual submission/fencing, then unreserving, and finally some more copy_to_user in vmw_execbuf_copy_fence_user. Glossing over tons of details, but looks all safe. - vmw_fence_event_ioctl: No ttm_reserve/dma_resv_lock anywhere to be seen, seems to only create a fence and copy it out. - a pile of smaller ioctl in vmwgfx_ioctl.c, no reservations to be found there. Summary: vmwgfx seems to be fine too. - virtio: There's virtio_gpu_execbuffer_ioctl, which does all the copying from userspace before even looking up objects through their handles, so safe. Plus the getparam/getcaps ioctl, also both safe. - qxl only has qxl_execbuffer_ioctl, which calls into qxl_process_single_command. There's a lovely comment before the __copy_from_user_inatomic that the slowpath should be copied from i915, but I guess that never happened. Try not to be unlucky and get your CS data evicted between when it's written and the kernel tries to read it. The only other copy_from_user is for relocs, but those are done before qxl_release_reserve_list(), which seems to be the only thing reserving buffers (in the ttm/dma_resv sense) in that code. So looks safe. - A debugfs file in nouveau_debugfs_pstate_set() and the usif ioctl in usif_ioctl() look safe. nouveau_gem_ioctl_pushbuf() otoh breaks this everywhere and needs to be fixed up. v2: Thomas pointed at that vmwgfx calls dma_resv_init while it holds a dma_resv lock of a different object already. Christian mentioned that ttm core does this too for ghost objects. intel-gfx-ci highlighted that i915 has similar issues. Unfortunately we can't do this in the usual module init functions, because kernel threads don't have an ->mm - we have to wait around for some user thread to do this. Solution is to spawn a worker (but only once). It's horrible, but it works. Cc: Alex Deucher <alexander.deucher@amd.com> Cc: Christian König <christian.koenig@amd.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Rob Herring <robh@kernel.org> Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com> Cc: Eric Anholt <eric@anholt.net> Cc: Dave Airlie <airlied@redhat.com> Cc: Gerd Hoffmann <kraxel@redhat.com> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: "VMware Graphics" <linux-graphics-maintainer@vmware.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> --- drivers/dma-buf/dma-resv.c | 42 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+)