| Message ID | 20240122141007.401490-6-janusz.krzysztofik@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: Fix VMA UAF on destroy against deactivate race | expand |
On Mon, Jan 22, 2024 at 03:04:42PM +0100, Janusz Krzysztofik wrote: > Object debugging tools were sporadically reporting illegal attempts to > free a still active i915 VMA object when parking a GPU tile believed to be > idle. > > [161.359441] ODEBUG: free active (active state 0) object: ffff88811643b958 object type: i915_active hint: __i915_vma_active+0x0/0x50 [i915] > [161.360082] WARNING: CPU: 5 PID: 276 at lib/debugobjects.c:514 debug_print_object+0x80/0xb0 > ... > [161.360304] CPU: 5 PID: 276 Comm: kworker/5:2 Not tainted 6.5.0-rc1-CI_DRM_13375-g003f860e5577+ #1 > [161.360314] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022 > [161.360322] Workqueue: i915-unordered __intel_wakeref_put_work [i915] > [161.360592] RIP: 0010:debug_print_object+0x80/0xb0 > ... > [161.361347] debug_object_free+0xeb/0x110 > [161.361362] i915_active_fini+0x14/0x130 [i915] > [161.361866] release_references+0xfe/0x1f0 [i915] > [161.362543] i915_vma_parked+0x1db/0x380 [i915] > [161.363129] __gt_park+0x121/0x230 [i915] > [161.363515] ____intel_wakeref_put_last+0x1f/0x70 [i915] > > That has been tracked down to be happening when another thread is > deactivating the VMA inside __active_retire() helper, after the VMA's > active counter has been already decremented to 0, but before deactivation > of the VMA's object is reported to the object debugging tool. > > We could prevent from that race by serializing i915_active_fini() with > __active_retire() via ref->tree_lock, but that wouldn't stop the VMA from > being used, e.g. from __i915_vma_retire() called at the end of > __active_retire(), after that VMA has been already freed by a concurrent > i915_vma_destroy() on return from the i915_active_fini(). Then, we should > rather fix the issue at the VMA level, not in i915_active. > > Since __i915_vma_parked() is called from __gt_park() on last put of the > GT's wakeref, the issue could be addressed by holding the GT wakeref long > enough for __active_retire() to complete before that wakeref is released > and the GT parked. > > A VMA associated with a request doesn't acquire a GT wakeref by itself. > Instead, it depends on a wakeref held directly by the request's active > intel_context for a GT associated with its VM, and indirectly on that > intel_context's engine wakeref if the engine belongs to the same GT as the > VMA's VM. In case of single-tile platforms, at least one of those > wakerefs is usually held long enough for the request's VMA to be > deactivated on time, before it is destroyed on last put of its VM GT > wakeref. However, on multi-tile platforms, a request may use a VMA from a > tile other than the one that hosts the request's engine, then it is > protected only with the intel_context's VM GT wakeref. > > There was an attempt to fix this issue on 2-tile Meteor Lake by acquiring please do not confuse the terminology here. MTL is 1-tile platform, with multiple GTs (1 for Render/Compute and 1 for Media). Also you could probably avoid mentioning the other case here when you are actively trying to resolve the RKL's single GT case. > an extra wakeref for a Primary GT from i915_gem_do_execbuffer() -- see > commit f56fe3e91787 ("drm/i915: Fix a VMA UAF for multi-gt platform"). > However, it occurred insufficient -- the issue was still reported by CI. > That wakeref was released on exit from i915_gem_do_execbuffer(), then > potentially before completion of the request and deactivation of its > associated VMAs. > > OTOH, CI reports indicate that single-tile platforms also suffer > sporadically from the same race. > > I believe the issue was introduced by commit d93939730347 ("drm/i915: > Remove the vma refcount") which moved a call to i915_active_fini() from > a dropped i915_vma_release(), called on last put of the removed VMA kref, > to i915_vma_parked() processing path called on last put of a GT wakeref. > However, its visibility to the object debugging tool was suppressed by a > bug in i915_active that was fixed two weeks later with commit e92eb246feb9 > ("drm/i915/active: Fix missing debug object activation"). > > Fix the issue by getting a wakeref for the VMA's tile when activating it, > and putting that wakeref only after the VMA is deactivated. However, > exclude global GTT from that processing path, otherwise the GPU never goes > idle. Since __i915_vma_retire() may be called from atomic contexts, use > async variant of wakeref put. okay, this explains the first block of the patch below, but I'm afraid that it doesn't explain why: - if (flags & PIN_GLOBAL) > > v4: Refresh on top of commit 5e4e06e4087e ("drm/i915: Track gt pm > wakerefs") (Andi), > - for more easy backporting, split out removal of former insufficient > workarounds and move them to separate patches (Nirmoy). > - clean up commit message and description a bit. > v3: Identify root cause more precisely, and a commit to blame, > - identify and drop former workarounds, > - update commit message and description. > v2: Get the wakeref before VM mutex to avoid circular locking dependency, > - drop questionable Fixes: tag. > > Fixes: d93939730347 ("drm/i915: Remove the vma refcount") > Closes: https://gitlab.freedesktop.org/drm/intel/issues/8875 > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com> > Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> > Cc: Nirmoy Das <nirmoy.das@intel.com> > Cc: Andi Shyti <andi.shyti@linux.intel.com> > Cc: stable@vger.kernel.org # v5.19+ > --- > drivers/gpu/drm/i915/i915_vma.c | 26 +++++++++++++++++++------- > drivers/gpu/drm/i915/i915_vma_types.h | 1 + > 2 files changed, 20 insertions(+), 7 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c > index d09aad34ba37f..604d420b9e1fd 100644 > --- a/drivers/gpu/drm/i915/i915_vma.c > +++ b/drivers/gpu/drm/i915/i915_vma.c > @@ -34,6 +34,7 @@ > #include "gt/intel_engine.h" > #include "gt/intel_engine_heartbeat.h" > #include "gt/intel_gt.h" > +#include "gt/intel_gt_pm.h" > #include "gt/intel_gt_requests.h" > #include "gt/intel_tlb.h" > > @@ -103,12 +104,25 @@ static inline struct i915_vma *active_to_vma(struct i915_active *ref) > > static int __i915_vma_active(struct i915_active *ref) > { > - return i915_vma_tryget(active_to_vma(ref)) ? 0 : -ENOENT; > + struct i915_vma *vma = active_to_vma(ref); > + > + if (!i915_vma_tryget(vma)) > + return -ENOENT; > + > + if (!i915_vma_is_ggtt(vma)) > + vma->wakeref = intel_gt_pm_get(vma->vm->gt); > + > + return 0; > } > > static void __i915_vma_retire(struct i915_active *ref) > { > - i915_vma_put(active_to_vma(ref)); > + struct i915_vma *vma = active_to_vma(ref); > + > + if (!i915_vma_is_ggtt(vma)) > + intel_gt_pm_put_async(vma->vm->gt, vma->wakeref); > + > + i915_vma_put(vma); > } > > static struct i915_vma * > @@ -1404,7 +1418,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > struct i915_vma_work *work = NULL; > struct dma_fence *moving = NULL; > struct i915_vma_resource *vma_res = NULL; > - intel_wakeref_t wakeref = 0; > + intel_wakeref_t wakeref; > unsigned int bound; > int err; > > @@ -1424,8 +1438,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > if (err) > return err; > > - if (flags & PIN_GLOBAL) > - wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm); > + wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm); > > if (flags & vma->vm->bind_async_flags) { > /* lock VM */ > @@ -1561,8 +1574,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > if (work) > dma_fence_work_commit_imm(&work->base); > err_rpm: > - if (wakeref) > - intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref); > + intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref); > > if (moving) > dma_fence_put(moving); > diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h > index 64472b7f0e770..f0086fadff4d3 100644 > --- a/drivers/gpu/drm/i915/i915_vma_types.h > +++ b/drivers/gpu/drm/i915/i915_vma_types.h > @@ -264,6 +264,7 @@ struct i915_vma { > #define I915_VMA_SCANOUT ((int)BIT(I915_VMA_SCANOUT_BIT)) > > struct i915_active active; > + intel_wakeref_t wakeref; > > #define I915_VMA_PAGES_BIAS 24 > #define I915_VMA_PAGES_ACTIVE (BIT(24) | 1) > -- > 2.43.0 >
Hi Rodrigo, Thank you for review. On Monday, 22 January 2024 22:09:38 CET Rodrigo Vivi wrote: > On Mon, Jan 22, 2024 at 03:04:42PM +0100, Janusz Krzysztofik wrote: > > Object debugging tools were sporadically reporting illegal attempts to > > free a still active i915 VMA object when parking a GPU tile believed to be > > idle. > > > > [161.359441] ODEBUG: free active (active state 0) object: ffff88811643b958 object type: i915_active hint: __i915_vma_active+0x0/0x50 [i915] > > [161.360082] WARNING: CPU: 5 PID: 276 at lib/debugobjects.c:514 debug_print_object+0x80/0xb0 > > ... > > [161.360304] CPU: 5 PID: 276 Comm: kworker/5:2 Not tainted 6.5.0-rc1-CI_DRM_13375-g003f860e5577+ #1 > > [161.360314] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022 > > [161.360322] Workqueue: i915-unordered __intel_wakeref_put_work [i915] > > [161.360592] RIP: 0010:debug_print_object+0x80/0xb0 > > ... > > [161.361347] debug_object_free+0xeb/0x110 > > [161.361362] i915_active_fini+0x14/0x130 [i915] > > [161.361866] release_references+0xfe/0x1f0 [i915] > > [161.362543] i915_vma_parked+0x1db/0x380 [i915] > > [161.363129] __gt_park+0x121/0x230 [i915] > > [161.363515] ____intel_wakeref_put_last+0x1f/0x70 [i915] > > > > That has been tracked down to be happening when another thread is > > deactivating the VMA inside __active_retire() helper, after the VMA's > > active counter has been already decremented to 0, but before deactivation > > of the VMA's object is reported to the object debugging tool. > > > > We could prevent from that race by serializing i915_active_fini() with > > __active_retire() via ref->tree_lock, but that wouldn't stop the VMA from > > being used, e.g. from __i915_vma_retire() called at the end of > > __active_retire(), after that VMA has been already freed by a concurrent > > i915_vma_destroy() on return from the i915_active_fini(). Then, we should > > rather fix the issue at the VMA level, not in i915_active. > > > > Since __i915_vma_parked() is called from __gt_park() on last put of the > > GT's wakeref, the issue could be addressed by holding the GT wakeref long > > enough for __active_retire() to complete before that wakeref is released > > and the GT parked. > > > > A VMA associated with a request doesn't acquire a GT wakeref by itself. > > Instead, it depends on a wakeref held directly by the request's active > > intel_context for a GT associated with its VM, and indirectly on that > > intel_context's engine wakeref if the engine belongs to the same GT as the > > VMA's VM. In case of single-tile platforms, at least one of those > > wakerefs is usually held long enough for the request's VMA to be > > deactivated on time, before it is destroyed on last put of its VM GT > > wakeref. However, on multi-tile platforms, a request may use a VMA from a > > tile other than the one that hosts the request's engine, then it is > > protected only with the intel_context's VM GT wakeref. > > > > There was an attempt to fix this issue on 2-tile Meteor Lake by acquiring > > please do not confuse the terminology here. MTL is 1-tile platform, > with multiple GTs (1 for Render/Compute and 1 for Media). I didn't realize that "tile" is not the same as "GT". I can review the whole description and replace all occurrences of "tile" with "GT". > > Also you could probably avoid mentioning the other case here when > you are actively trying to resolve the RKL's single GT case. OK, but let me keep that part of commit description in the cover letter then, because: - historically, the issue was more frequently reproduced in CI on MTL than on other platforms, and that was the initial scope I started working on, - the full description as is better reflects phases of my process of reproduction and root cause analysis of the issue, - the MTL case was specifically addressed by the former insufficient workaround which now I'm now proposing to drop. > > an extra wakeref for a Primary GT from i915_gem_do_execbuffer() -- see > > commit f56fe3e91787 ("drm/i915: Fix a VMA UAF for multi-gt platform"). > > However, it occurred insufficient -- the issue was still reported by CI. > > That wakeref was released on exit from i915_gem_do_execbuffer(), then > > potentially before completion of the request and deactivation of its > > associated VMAs. > > > > OTOH, CI reports indicate that single-tile platforms also suffer > > sporadically from the same race. > > > > I believe the issue was introduced by commit d93939730347 ("drm/i915: > > Remove the vma refcount") which moved a call to i915_active_fini() from > > a dropped i915_vma_release(), called on last put of the removed VMA kref, > > to i915_vma_parked() processing path called on last put of a GT wakeref. > > However, its visibility to the object debugging tool was suppressed by a > > bug in i915_active that was fixed two weeks later with commit e92eb246feb9 > > ("drm/i915/active: Fix missing debug object activation"). > > > > Fix the issue by getting a wakeref for the VMA's tile when activating it, > > and putting that wakeref only after the VMA is deactivated. However, > > exclude global GTT from that processing path, otherwise the GPU never goes > > idle. Since __i915_vma_retire() may be called from atomic contexts, use > > async variant of wakeref put. > > okay, this explains the first block of the patch below, but I'm afraid > that it doesn't explain why: > > - if (flags & PIN_GLOBAL) That's explained in v2 changelog below, I believe. I can add that information to the body of commit description as well. Thanks, Janusz > > > > v4: Refresh on top of commit 5e4e06e4087e ("drm/i915: Track gt pm > > wakerefs") (Andi), > > - for more easy backporting, split out removal of former insufficient > > workarounds and move them to separate patches (Nirmoy). > > - clean up commit message and description a bit. > > v3: Identify root cause more precisely, and a commit to blame, > > - identify and drop former workarounds, > > - update commit message and description. > > v2: Get the wakeref before VM mutex to avoid circular locking dependency, > > - drop questionable Fixes: tag. > > > > Fixes: d93939730347 ("drm/i915: Remove the vma refcount") > > Closes: https://gitlab.freedesktop.org/drm/intel/issues/8875 > > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com> > > Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> > > Cc: Nirmoy Das <nirmoy.das@intel.com> > > Cc: Andi Shyti <andi.shyti@linux.intel.com> > > Cc: stable@vger.kernel.org # v5.19+ > > --- > > drivers/gpu/drm/i915/i915_vma.c | 26 +++++++++++++++++++------- > > drivers/gpu/drm/i915/i915_vma_types.h | 1 + > > 2 files changed, 20 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c > > index d09aad34ba37f..604d420b9e1fd 100644 > > --- a/drivers/gpu/drm/i915/i915_vma.c > > +++ b/drivers/gpu/drm/i915/i915_vma.c > > @@ -34,6 +34,7 @@ > > #include "gt/intel_engine.h" > > #include "gt/intel_engine_heartbeat.h" > > #include "gt/intel_gt.h" > > +#include "gt/intel_gt_pm.h" > > #include "gt/intel_gt_requests.h" > > #include "gt/intel_tlb.h" > > > > @@ -103,12 +104,25 @@ static inline struct i915_vma *active_to_vma(struct i915_active *ref) > > > > static int __i915_vma_active(struct i915_active *ref) > > { > > - return i915_vma_tryget(active_to_vma(ref)) ? 0 : -ENOENT; > > + struct i915_vma *vma = active_to_vma(ref); > > + > > + if (!i915_vma_tryget(vma)) > > + return -ENOENT; > > + > > + if (!i915_vma_is_ggtt(vma)) > > + vma->wakeref = intel_gt_pm_get(vma->vm->gt); > > + > > + return 0; > > } > > > > static void __i915_vma_retire(struct i915_active *ref) > > { > > - i915_vma_put(active_to_vma(ref)); > > + struct i915_vma *vma = active_to_vma(ref); > > + > > + if (!i915_vma_is_ggtt(vma)) > > + intel_gt_pm_put_async(vma->vm->gt, vma->wakeref); > > + > > + i915_vma_put(vma); > > } > > > > static struct i915_vma * > > @@ -1404,7 +1418,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > > struct i915_vma_work *work = NULL; > > struct dma_fence *moving = NULL; > > struct i915_vma_resource *vma_res = NULL; > > - intel_wakeref_t wakeref = 0; > > + intel_wakeref_t wakeref; > > unsigned int bound; > > int err; > > > > @@ -1424,8 +1438,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > > if (err) > > return err; > > > > - if (flags & PIN_GLOBAL) > > - wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm); > > + wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm); > > > > if (flags & vma->vm->bind_async_flags) { > > /* lock VM */ > > @@ -1561,8 +1574,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > > if (work) > > dma_fence_work_commit_imm(&work->base); > > err_rpm: > > - if (wakeref) > > - intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref); > > + intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref); > > > > if (moving) > > dma_fence_put(moving); > > diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h > > index 64472b7f0e770..f0086fadff4d3 100644 > > --- a/drivers/gpu/drm/i915/i915_vma_types.h > > +++ b/drivers/gpu/drm/i915/i915_vma_types.h > > @@ -264,6 +264,7 @@ struct i915_vma { > > #define I915_VMA_SCANOUT ((int)BIT(I915_VMA_SCANOUT_BIT)) > > > > struct i915_active active; > > + intel_wakeref_t wakeref; > > > > #define I915_VMA_PAGES_BIAS 24 > > #define I915_VMA_PAGES_ACTIVE (BIT(24) | 1) >
On Tue, Jan 23, 2024 at 11:51:15AM +0100, Janusz Krzysztofik wrote: > Hi Rodrigo, > > Thank you for review. > > On Monday, 22 January 2024 22:09:38 CET Rodrigo Vivi wrote: > > On Mon, Jan 22, 2024 at 03:04:42PM +0100, Janusz Krzysztofik wrote: > > > Object debugging tools were sporadically reporting illegal attempts to > > > free a still active i915 VMA object when parking a GPU tile believed to be > > > idle. > > > > > > [161.359441] ODEBUG: free active (active state 0) object: ffff88811643b958 object type: i915_active hint: __i915_vma_active+0x0/0x50 [i915] > > > [161.360082] WARNING: CPU: 5 PID: 276 at lib/debugobjects.c:514 debug_print_object+0x80/0xb0 > > > ... > > > [161.360304] CPU: 5 PID: 276 Comm: kworker/5:2 Not tainted 6.5.0-rc1-CI_DRM_13375-g003f860e5577+ #1 > > > [161.360314] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022 > > > [161.360322] Workqueue: i915-unordered __intel_wakeref_put_work [i915] > > > [161.360592] RIP: 0010:debug_print_object+0x80/0xb0 > > > ... > > > [161.361347] debug_object_free+0xeb/0x110 > > > [161.361362] i915_active_fini+0x14/0x130 [i915] > > > [161.361866] release_references+0xfe/0x1f0 [i915] > > > [161.362543] i915_vma_parked+0x1db/0x380 [i915] > > > [161.363129] __gt_park+0x121/0x230 [i915] > > > [161.363515] ____intel_wakeref_put_last+0x1f/0x70 [i915] > > > > > > That has been tracked down to be happening when another thread is > > > deactivating the VMA inside __active_retire() helper, after the VMA's > > > active counter has been already decremented to 0, but before deactivation > > > of the VMA's object is reported to the object debugging tool. > > > > > > We could prevent from that race by serializing i915_active_fini() with > > > __active_retire() via ref->tree_lock, but that wouldn't stop the VMA from > > > being used, e.g. from __i915_vma_retire() called at the end of > > > __active_retire(), after that VMA has been already freed by a concurrent > > > i915_vma_destroy() on return from the i915_active_fini(). Then, we should > > > rather fix the issue at the VMA level, not in i915_active. > > > > > > Since __i915_vma_parked() is called from __gt_park() on last put of the > > > GT's wakeref, the issue could be addressed by holding the GT wakeref long > > > enough for __active_retire() to complete before that wakeref is released > > > and the GT parked. > > > > > > A VMA associated with a request doesn't acquire a GT wakeref by itself. > > > Instead, it depends on a wakeref held directly by the request's active > > > intel_context for a GT associated with its VM, and indirectly on that > > > intel_context's engine wakeref if the engine belongs to the same GT as the > > > VMA's VM. In case of single-tile platforms, at least one of those > > > wakerefs is usually held long enough for the request's VMA to be > > > deactivated on time, before it is destroyed on last put of its VM GT > > > wakeref. However, on multi-tile platforms, a request may use a VMA from a > > > tile other than the one that hosts the request's engine, then it is > > > protected only with the intel_context's VM GT wakeref. > > > > > > There was an attempt to fix this issue on 2-tile Meteor Lake by acquiring > > > > please do not confuse the terminology here. MTL is 1-tile platform, > > with multiple GTs (1 for Render/Compute and 1 for Media). > > I didn't realize that "tile" is not the same as "GT". I can review the whole > description and replace all occurrences of "tile" with "GT". yeap, in i915 it is a 1-1 map... a tile is implemented within the intel_gt. In Xe there's a good split and a good doc picture is here: https://dri.freedesktop.org/docs/drm/gpu/driver-uapi.html#drm-xe-uapi > > > > > Also you could probably avoid mentioning the other case here when > > you are actively trying to resolve the RKL's single GT case. > > OK, but let me keep that part of commit description in the cover letter then, > because: > - historically, the issue was more frequently reproduced in CI on MTL than on > other platforms, and that was the initial scope I started working on, > - the full description as is better reflects phases of my process of > reproduction and root cause analysis of the issue, > - the MTL case was specifically addressed by the former insufficient > workaround which now I'm now proposing to drop. > > > > an extra wakeref for a Primary GT from i915_gem_do_execbuffer() -- see > > > commit f56fe3e91787 ("drm/i915: Fix a VMA UAF for multi-gt platform"). > > > However, it occurred insufficient -- the issue was still reported by CI. > > > That wakeref was released on exit from i915_gem_do_execbuffer(), then > > > potentially before completion of the request and deactivation of its > > > associated VMAs. > > > > > > OTOH, CI reports indicate that single-tile platforms also suffer > > > sporadically from the same race. > > > > > > I believe the issue was introduced by commit d93939730347 ("drm/i915: > > > Remove the vma refcount") which moved a call to i915_active_fini() from > > > a dropped i915_vma_release(), called on last put of the removed VMA kref, > > > to i915_vma_parked() processing path called on last put of a GT wakeref. > > > However, its visibility to the object debugging tool was suppressed by a > > > bug in i915_active that was fixed two weeks later with commit e92eb246feb9 > > > ("drm/i915/active: Fix missing debug object activation"). > > > > > > Fix the issue by getting a wakeref for the VMA's tile when activating it, > > > and putting that wakeref only after the VMA is deactivated. However, > > > exclude global GTT from that processing path, otherwise the GPU never goes > > > idle. Since __i915_vma_retire() may be called from atomic contexts, use > > > async variant of wakeref put. > > > > okay, this explains the first block of the patch below, but I'm afraid > > that it doesn't explain why: > > > > - if (flags & PIN_GLOBAL) > > That's explained in v2 changelog below, I believe. I can add that information > to the body of commit description as well. > > Thanks, > Janusz > > > > > > > > v4: Refresh on top of commit 5e4e06e4087e ("drm/i915: Track gt pm > > > wakerefs") (Andi), > > > - for more easy backporting, split out removal of former insufficient > > > workarounds and move them to separate patches (Nirmoy). > > > - clean up commit message and description a bit. > > > v3: Identify root cause more precisely, and a commit to blame, > > > - identify and drop former workarounds, > > > - update commit message and description. > > > v2: Get the wakeref before VM mutex to avoid circular locking dependency, > > > - drop questionable Fixes: tag. > > > > > > Fixes: d93939730347 ("drm/i915: Remove the vma refcount") > > > Closes: https://gitlab.freedesktop.org/drm/intel/issues/8875 > > > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com> > > > Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> > > > Cc: Nirmoy Das <nirmoy.das@intel.com> > > > Cc: Andi Shyti <andi.shyti@linux.intel.com> > > > Cc: stable@vger.kernel.org # v5.19+ > > > --- > > > drivers/gpu/drm/i915/i915_vma.c | 26 +++++++++++++++++++------- > > > drivers/gpu/drm/i915/i915_vma_types.h | 1 + > > > 2 files changed, 20 insertions(+), 7 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c > > > index d09aad34ba37f..604d420b9e1fd 100644 > > > --- a/drivers/gpu/drm/i915/i915_vma.c > > > +++ b/drivers/gpu/drm/i915/i915_vma.c > > > @@ -34,6 +34,7 @@ > > > #include "gt/intel_engine.h" > > > #include "gt/intel_engine_heartbeat.h" > > > #include "gt/intel_gt.h" > > > +#include "gt/intel_gt_pm.h" > > > #include "gt/intel_gt_requests.h" > > > #include "gt/intel_tlb.h" > > > > > > @@ -103,12 +104,25 @@ static inline struct i915_vma *active_to_vma(struct i915_active *ref) > > > > > > static int __i915_vma_active(struct i915_active *ref) > > > { > > > - return i915_vma_tryget(active_to_vma(ref)) ? 0 : -ENOENT; > > > + struct i915_vma *vma = active_to_vma(ref); > > > + > > > + if (!i915_vma_tryget(vma)) > > > + return -ENOENT; > > > + > > > + if (!i915_vma_is_ggtt(vma)) > > > + vma->wakeref = intel_gt_pm_get(vma->vm->gt); > > > + > > > + return 0; > > > } > > > > > > static void __i915_vma_retire(struct i915_active *ref) > > > { > > > - i915_vma_put(active_to_vma(ref)); > > > + struct i915_vma *vma = active_to_vma(ref); > > > + > > > + if (!i915_vma_is_ggtt(vma)) > > > + intel_gt_pm_put_async(vma->vm->gt, vma->wakeref); > > > + > > > + i915_vma_put(vma); > > > } > > > > > > static struct i915_vma * > > > @@ -1404,7 +1418,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > > > struct i915_vma_work *work = NULL; > > > struct dma_fence *moving = NULL; > > > struct i915_vma_resource *vma_res = NULL; > > > - intel_wakeref_t wakeref = 0; > > > + intel_wakeref_t wakeref; > > > unsigned int bound; > > > int err; > > > > > > @@ -1424,8 +1438,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > > > if (err) > > > return err; > > > > > > - if (flags & PIN_GLOBAL) > > > - wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm); > > > + wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm); > > > > > > if (flags & vma->vm->bind_async_flags) { > > > /* lock VM */ > > > @@ -1561,8 +1574,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, > > > if (work) > > > dma_fence_work_commit_imm(&work->base); > > > err_rpm: > > > - if (wakeref) > > > - intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref); > > > + intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref); > > > > > > if (moving) > > > dma_fence_put(moving); > > > diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h > > > index 64472b7f0e770..f0086fadff4d3 100644 > > > --- a/drivers/gpu/drm/i915/i915_vma_types.h > > > +++ b/drivers/gpu/drm/i915/i915_vma_types.h > > > @@ -264,6 +264,7 @@ struct i915_vma { > > > #define I915_VMA_SCANOUT ((int)BIT(I915_VMA_SCANOUT_BIT)) > > > > > > struct i915_active active; > > > + intel_wakeref_t wakeref; > > > > > > #define I915_VMA_PAGES_BIAS 24 > > > #define I915_VMA_PAGES_ACTIVE (BIT(24) | 1) > > > > > >
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c index d09aad34ba37f..604d420b9e1fd 100644 --- a/drivers/gpu/drm/i915/i915_vma.c +++ b/drivers/gpu/drm/i915/i915_vma.c @@ -34,6 +34,7 @@ #include "gt/intel_engine.h" #include "gt/intel_engine_heartbeat.h" #include "gt/intel_gt.h" +#include "gt/intel_gt_pm.h" #include "gt/intel_gt_requests.h" #include "gt/intel_tlb.h" @@ -103,12 +104,25 @@ static inline struct i915_vma *active_to_vma(struct i915_active *ref) static int __i915_vma_active(struct i915_active *ref) { - return i915_vma_tryget(active_to_vma(ref)) ? 0 : -ENOENT; + struct i915_vma *vma = active_to_vma(ref); + + if (!i915_vma_tryget(vma)) + return -ENOENT; + + if (!i915_vma_is_ggtt(vma)) + vma->wakeref = intel_gt_pm_get(vma->vm->gt); + + return 0; } static void __i915_vma_retire(struct i915_active *ref) { - i915_vma_put(active_to_vma(ref)); + struct i915_vma *vma = active_to_vma(ref); + + if (!i915_vma_is_ggtt(vma)) + intel_gt_pm_put_async(vma->vm->gt, vma->wakeref); + + i915_vma_put(vma); } static struct i915_vma * @@ -1404,7 +1418,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, struct i915_vma_work *work = NULL; struct dma_fence *moving = NULL; struct i915_vma_resource *vma_res = NULL; - intel_wakeref_t wakeref = 0; + intel_wakeref_t wakeref; unsigned int bound; int err; @@ -1424,8 +1438,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, if (err) return err; - if (flags & PIN_GLOBAL) - wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm); + wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm); if (flags & vma->vm->bind_async_flags) { /* lock VM */ @@ -1561,8 +1574,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, if (work) dma_fence_work_commit_imm(&work->base); err_rpm: - if (wakeref) - intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref); + intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref); if (moving) dma_fence_put(moving); diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h index 64472b7f0e770..f0086fadff4d3 100644 --- a/drivers/gpu/drm/i915/i915_vma_types.h +++ b/drivers/gpu/drm/i915/i915_vma_types.h @@ -264,6 +264,7 @@ struct i915_vma { #define I915_VMA_SCANOUT ((int)BIT(I915_VMA_SCANOUT_BIT)) struct i915_active active; + intel_wakeref_t wakeref; #define I915_VMA_PAGES_BIAS 24 #define I915_VMA_PAGES_ACTIVE (BIT(24) | 1)
Object debugging tools were sporadically reporting illegal attempts to free a still active i915 VMA object when parking a GPU tile believed to be idle. [161.359441] ODEBUG: free active (active state 0) object: ffff88811643b958 object type: i915_active hint: __i915_vma_active+0x0/0x50 [i915] [161.360082] WARNING: CPU: 5 PID: 276 at lib/debugobjects.c:514 debug_print_object+0x80/0xb0 ... [161.360304] CPU: 5 PID: 276 Comm: kworker/5:2 Not tainted 6.5.0-rc1-CI_DRM_13375-g003f860e5577+ #1 [161.360314] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022 [161.360322] Workqueue: i915-unordered __intel_wakeref_put_work [i915] [161.360592] RIP: 0010:debug_print_object+0x80/0xb0 ... [161.361347] debug_object_free+0xeb/0x110 [161.361362] i915_active_fini+0x14/0x130 [i915] [161.361866] release_references+0xfe/0x1f0 [i915] [161.362543] i915_vma_parked+0x1db/0x380 [i915] [161.363129] __gt_park+0x121/0x230 [i915] [161.363515] ____intel_wakeref_put_last+0x1f/0x70 [i915] That has been tracked down to be happening when another thread is deactivating the VMA inside __active_retire() helper, after the VMA's active counter has been already decremented to 0, but before deactivation of the VMA's object is reported to the object debugging tool. We could prevent from that race by serializing i915_active_fini() with __active_retire() via ref->tree_lock, but that wouldn't stop the VMA from being used, e.g. from __i915_vma_retire() called at the end of __active_retire(), after that VMA has been already freed by a concurrent i915_vma_destroy() on return from the i915_active_fini(). Then, we should rather fix the issue at the VMA level, not in i915_active. Since __i915_vma_parked() is called from __gt_park() on last put of the GT's wakeref, the issue could be addressed by holding the GT wakeref long enough for __active_retire() to complete before that wakeref is released and the GT parked. A VMA associated with a request doesn't acquire a GT wakeref by itself. Instead, it depends on a wakeref held directly by the request's active intel_context for a GT associated with its VM, and indirectly on that intel_context's engine wakeref if the engine belongs to the same GT as the VMA's VM. In case of single-tile platforms, at least one of those wakerefs is usually held long enough for the request's VMA to be deactivated on time, before it is destroyed on last put of its VM GT wakeref. However, on multi-tile platforms, a request may use a VMA from a tile other than the one that hosts the request's engine, then it is protected only with the intel_context's VM GT wakeref. There was an attempt to fix this issue on 2-tile Meteor Lake by acquiring an extra wakeref for a Primary GT from i915_gem_do_execbuffer() -- see commit f56fe3e91787 ("drm/i915: Fix a VMA UAF for multi-gt platform"). However, it occurred insufficient -- the issue was still reported by CI. That wakeref was released on exit from i915_gem_do_execbuffer(), then potentially before completion of the request and deactivation of its associated VMAs. OTOH, CI reports indicate that single-tile platforms also suffer sporadically from the same race. I believe the issue was introduced by commit d93939730347 ("drm/i915: Remove the vma refcount") which moved a call to i915_active_fini() from a dropped i915_vma_release(), called on last put of the removed VMA kref, to i915_vma_parked() processing path called on last put of a GT wakeref. However, its visibility to the object debugging tool was suppressed by a bug in i915_active that was fixed two weeks later with commit e92eb246feb9 ("drm/i915/active: Fix missing debug object activation"). Fix the issue by getting a wakeref for the VMA's tile when activating it, and putting that wakeref only after the VMA is deactivated. However, exclude global GTT from that processing path, otherwise the GPU never goes idle. Since __i915_vma_retire() may be called from atomic contexts, use async variant of wakeref put. v4: Refresh on top of commit 5e4e06e4087e ("drm/i915: Track gt pm wakerefs") (Andi), - for more easy backporting, split out removal of former insufficient workarounds and move them to separate patches (Nirmoy). - clean up commit message and description a bit. v3: Identify root cause more precisely, and a commit to blame, - identify and drop former workarounds, - update commit message and description. v2: Get the wakeref before VM mutex to avoid circular locking dependency, - drop questionable Fixes: tag. Fixes: d93939730347 ("drm/i915: Remove the vma refcount") Closes: https://gitlab.freedesktop.org/drm/intel/issues/8875 Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Nirmoy Das <nirmoy.das@intel.com> Cc: Andi Shyti <andi.shyti@linux.intel.com> Cc: stable@vger.kernel.org # v5.19+ --- drivers/gpu/drm/i915/i915_vma.c | 26 +++++++++++++++++++------- drivers/gpu/drm/i915/i915_vma_types.h | 1 + 2 files changed, 20 insertions(+), 7 deletions(-)