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authorDaniel Vetter <daniel.vetter@ffwll.ch>2019-11-04 18:37:59 +0100
committerDaniel Vetter <daniel.vetter@ffwll.ch>2019-11-06 11:23:15 +0100
commitb2a8116e25923643e9613ac5b65dd6e78dc5ee77 (patch)
treeac147a1d824c2692e1a9c2be40869355b5142d9b /drivers/dma-buf
parent8a537de0f3d8b655cb901c948ed863bf0b23277b (diff)
downloadlinux-b2a8116e25923643e9613ac5b65dd6e78dc5ee77.tar.bz2
dma_resv: prime lockdep annotations
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. v3: We can allocate mm! (Chris). Horrible worker hack out, clean initcall solution in. v4: Annotate with __init (Rob Herring) Cc: Rob Herring <robh@kernel.org> 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> Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com> Reviewed-by: Christian König <christian.koenig@amd.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Tested-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191104173801.2972-1-daniel.vetter@ffwll.ch
Diffstat (limited to 'drivers/dma-buf')
-rw-r--r--drivers/dma-buf/dma-resv.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 709002515550..a05ff542be22 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 +96,29 @@ static void dma_resv_list_free(struct dma_resv_list *list)
kfree_rcu(list, rcu);
}
+#if IS_ENABLED(CONFIG_LOCKDEP)
+static void __init dma_resv_lockdep(void)
+{
+ struct mm_struct *mm = mm_alloc();
+ struct dma_resv obj;
+
+ if (!mm)
+ return;
+
+ 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);
+}
+subsys_initcall(dma_resv_lockdep);
+#endif
+
/**
* dma_resv_init - initialize a reservation object
* @obj: the reservation object