Linaro-mm-sig

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3123 discussions

Re: CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is broken, was Re: [RFC PATCH 0/6] Deep talk about folio vmap

by Christoph Hellwig

On Mon, Apr 07, 2025 at 02:43:20PM +0800, Muchun Song wrote: > By the way, in case you truly struggle to comprehend the fundamental > aspects of HVO, I would like to summarize for you the user-visible > behaviors in comparison to the situation where HVO is disabled. > > HVO Status Tail Page Structures Head Page Structures > Enabled Read-Only (RO) Read-Write (RW) > Disabled Read-Write (RW) Read-Write (RW) > > The sole distinction between the two scenarios lies in whether the > tail page structures are allowed to be written or not. Please refrain > from getting bogged down in the details of the implementation of HVO. This feels extremely fragile to me. I doubt many people know what operations needs read vs write access to tail pages. Or for higher level operations if needs access to tail pages at all.

7 months

[PATCH v7 00/11] TEE subsystem for protected dma-buf allocations

by Jens Wiklander

Hi, This patch set allocates the protected DMA-bufs from a DMA-heap instantiated from the TEE subsystem. The TEE subsystem handles the DMA-buf allocations since it is the TEE (OP-TEE, AMD-TEE, TS-TEE, or perhaps a future QTEE) which sets up the protection for the memory used for the DMA-bufs. The DMA-heap uses a protected memory pool provided by the backend TEE driver, allowing it to choose how to allocate the protected physical memory. The allocated DMA-bufs must be imported with a new TEE_IOC_SHM_REGISTER_FD before they can be passed as arguments when requesting services from the secure world. Three use-cases (Secure Video Playback, Trusted UI, and Secure Video Recording) has been identified so far to serve as examples of what can be expected. The use-cases has predefined DMA-heap names, "protected,secure-video", "protected,trusted-ui", and "protected,secure-video-record". The backend driver registers protected memory pools for the use-cases it supports. Each use-case has it's own protected memory pool since different use-cases requires isolation from different parts of the system. A protected memory pool can be based on a static carveout instantiated while probing the TEE backend driver, or dynamically allocated from CMA and made protected as needed by the TEE. This can be tested on a RockPi 4B+ with the following steps: repo init -u https://github.com/jenswi-linaro/manifest.git -m rockpi4.xml \ -b prototype/sdp-v7 repo sync -j8 cd build make toolchains -j$(nproc) make all -j$(nproc) # Copy ../out/rockpi4.img to an SD card and boot the RockPi from that # Connect a monitor to the RockPi # login and at the prompt: gst-launch-1.0 videotestsrc ! \ aesenc key=1f9423681beb9a79215820f6bda73d0f \ iv=e9aa8e834d8d70b7e0d254ff670dd718 serialize-iv=true ! \ aesdec key=1f9423681beb9a79215820f6bda73d0f ! \ kmssink The aesdec module has been hacked to use an OP-TEE TA to decrypt the stream into protected DMA-bufs which are consumed by the kmssink. The primitive QEMU tests from previous patch set can be tested on RockPi in the same way with: xtest --sdp-basic The primitive test are tested on QEMU with the following steps: repo init -u https://github.com/jenswi-linaro/manifest.git -m qemu_v8.xml \ -b prototype/sdp-v7 repo sync -j8 cd build make toolchains -j$(nproc) make SPMC_AT_EL=1 all -j$(nproc) make SPMC_AT_EL=1 run-only # login and at the prompt: xtest --sdp-basic The SPMC_AT_EL=1 parameter configures the build with FF-A and an SPMC at S-EL1 inside OP-TEE. The parameter can be changed into SPMC_AT_EL=n to test without FF-A using the original SMC ABI instead. Please remember to do %rm -rf ../trusted-firmware-a/build/qemu for TF-A to be rebuilt properly using the new configuration. https://optee.readthedocs.io/en/latest/building/prerequisites.html list dependencies needed to build the above. The tests are pretty basic, mostly checking that a Trusted Application in the secure world can access and manipulate the memory. There are also some negative tests for out of bounds buffers etc. Thanks, Jens Changes since V6: * Restricted memory is now known as protected memory since to use the same term as https://docs.vulkan.org/guide/latest/protected.html. Update all patches to consistently use protected memory. * In "tee: implement protected DMA-heap" add the hidden config option TEE_DMABUF_HEAP to tell if the DMABUF_HEAPS functions are available for the TEE subsystem * Adding "tee: refactor params_from_user()", broken out from the patch "tee: new ioctl to a register tee_shm from a dmabuf file descriptor" * For "tee: new ioctl to a register tee_shm from a dmabuf file descriptor": - Update commit message to mention protected memory - Remove and open code tee_shm_get_parent_shm() in param_from_user_memref() * In "tee: add tee_shm_alloc_cma_phys_mem" add the hidden config option TEE_CMA to tell if the CMA functions are available for the TEE subsystem * For "tee: tee_device_alloc(): copy dma_mask from parent device" and "optee: pass parent device to tee_device_alloc", added Reviewed-by: Sumit Garg <sumit.garg(a)kernel.org> Changes since V5: * Removing "tee: add restricted memory allocation" and "tee: add TEE_IOC_RSTMEM_FD_INFO" * Adding "tee: implement restricted DMA-heap", "tee: new ioctl to a register tee_shm from a dmabuf file descriptor", "tee: add tee_shm_alloc_cma_phys_mem()", "optee: pass parent device to tee_device_alloc()", and "tee: tee_device_alloc(): copy dma_mask from parent device" * The two TEE driver OPs "rstmem_alloc()" and "rstmem_free()" are replaced with a struct tee_rstmem_pool abstraction. * Replaced the the TEE_IOC_RSTMEM_ALLOC user space API with the DMA-heap API Changes since V4: * Adding the patch "tee: add TEE_IOC_RSTMEM_FD_INFO" needed by the GStreamer demo * Removing the dummy CPU access and mmap functions from the dma_buf_ops * Fixing a compile error in "optee: FF-A: dynamic restricted memory allocation" reported by kernel test robot <lkp(a)intel.com> Changes since V3: * Make the use_case and flags field in struct tee_shm u32's instead of u16's * Add more description for TEE_IOC_RSTMEM_ALLOC in the header file * Import namespace DMA_BUF in module tee, reported by lkp(a)intel.com * Added a note in the commit message for "optee: account for direction while converting parameters" why it's needed * Factor out dynamic restricted memory allocation from "optee: support restricted memory allocation" into two new commits "optee: FF-A: dynamic restricted memory allocation" and "optee: smc abi: dynamic restricted memory allocation" * Guard CMA usage with #ifdef CONFIG_CMA, effectively disabling dynamic restricted memory allocate if CMA isn't configured Changes since the V2 RFC: * Based on v6.12 * Replaced the flags for SVP and Trusted UID memory with a u32 field with unique id for each use case * Added dynamic allocation of restricted memory pools * Added OP-TEE ABI both with and without FF-A for dynamic restricted memory * Added support for FF-A with FFA_LEND Changes since the V1 RFC: * Based on v6.11 * Complete rewrite, replacing the restricted heap with TEE_IOC_RSTMEM_ALLOC Changes since Olivier's post [2]: * Based on Yong Wu's post [1] where much of dma-buf handling is done in the generic restricted heap * Simplifications and cleanup * New commit message for "dma-buf: heaps: add Linaro restricted dmabuf heap support" * Replaced the word "secure" with "restricted" where applicable Etienne Carriere (1): tee: new ioctl to a register tee_shm from a dmabuf file descriptor Jens Wiklander (10): tee: tee_device_alloc(): copy dma_mask from parent device optee: pass parent device to tee_device_alloc() optee: account for direction while converting parameters optee: sync secure world ABI headers tee: implement protected DMA-heap tee: refactor params_from_user() tee: add tee_shm_alloc_cma_phys_mem() optee: support protected memory allocation optee: FF-A: dynamic protected memory allocation optee: smc abi: dynamic protected memory allocation drivers/tee/Kconfig | 10 + drivers/tee/Makefile | 1 + drivers/tee/optee/Makefile | 1 + drivers/tee/optee/call.c | 10 +- drivers/tee/optee/core.c | 1 + drivers/tee/optee/ffa_abi.c | 195 ++++++++++++- drivers/tee/optee/optee_ffa.h | 27 +- drivers/tee/optee/optee_msg.h | 83 +++++- drivers/tee/optee/optee_private.h | 55 +++- drivers/tee/optee/optee_smc.h | 71 ++++- drivers/tee/optee/protmem.c | 330 +++++++++++++++++++++ drivers/tee/optee/rpc.c | 31 +- drivers/tee/optee/smc_abi.c | 192 ++++++++++-- drivers/tee/tee_core.c | 157 +++++++--- drivers/tee/tee_heap.c | 469 ++++++++++++++++++++++++++++++ drivers/tee/tee_private.h | 16 + drivers/tee/tee_shm.c | 164 ++++++++++- include/linux/tee_core.h | 70 +++++ include/linux/tee_drv.h | 10 + include/uapi/linux/tee.h | 31 ++ 20 files changed, 1792 insertions(+), 132 deletions(-) create mode 100644 drivers/tee/optee/protmem.c create mode 100644 drivers/tee/tee_heap.c base-commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557 -- 2.43.0

7 months

Re: [PATCH v2] drm/nouveau: Prevent signalled fences in pending list

by Christian König

Am 03.04.25 um 16:40 schrieb Philipp Stanner: >>>>> >>>> >>>> That looks like a really really awkward approach. The driver >>>> basically uses a the DMA fence infrastructure as middle layer and >>>> callbacks into itself to cleanup it's own structures. >>>> >>> >>> What else are callbacks good for, if not to do something >>> automatically >>> when the fence gets signaled? >>> >> >> Well if you add a callback for a signal you issued yourself then >> that's kind of awkward. >> >> E.g. you call into the DMA fence code, just for the DMA fence code >> to call yourself back again. > Now we're entering CS-Philosophy, because it depends on who "you" and > "yourself" are. In case of the driver, yes, naturally it registers a > callback because at some other place (e.g., in the driver's interrupt > handler) the fence will be signaled and the driver wants the callback > stuff to be done. > > If that's not dma_fences' callbacks' purpose, then I'd be interested in > knowing what their purpose is, because from my POV this discussion > seems to imply that we effectively must never use them for anything. > > How could it ever be different? Who, for example, registers dma_fence > callbacks while not signaling them "himself"? Let me try to improve that explanation. First of all we have components, they can be drivers, frameworks, helpers like the DRM scheduler or generally any code which is more or less stand alone. The definition of components is a bit tricky, but in general people usually get what they mean. E.g. in this case here we have nouveau as single component. Now the DMA fence interface allows sending signals between different components in a standardized way, one component can send a signal to another one and they don't necessarily need to know anything from each other except that both are using the DMA fence framework in the documented manner. When a component is now both the provide and the consumer at the same time you actually need a reason for that. Could be for example that it wants to consume signals from both itself as well as others, but this doesn't apply for this use case here. Considering pool or billiard you can of course do a trick shot and try to hit the 8, but going straight for it just has a better chance to succeed. > > >> >> >>> >>>> >>>> Additional to that we don't guarantee any callback order for the >>>> DMA >>>> fence and so it can be that mix cleaning up the callback with >>>> other >>>> work which is certainly not good when you want to guarantee that >>>> the >>>> cleanup happens under the same lock. >>>> >>> >>> Isn't my perception correct that the primary issue you have with >>> this >>> approach is that dma_fence_put() is called from within the >>> callback? Or >>> do you also take issue with deleting from the list? >>> >> >> Well kind of both. The issue is that the caller of >> dma_fence_signal() or dma_fence_signal_locked() must hold the >> reference until the function returns. >> >> When you do the list cleanup and the drop inside the callback it is >> perfectly possible that the fence pointer becomes stale before you >> return and that's really not a good idea. > In other words, you would prefer if this patch would have a function > with my callback's code in a function, and that function would be > called at every place where the driver signals a fence? > > If that's your opinion, then, IOW, it would mean for us to go almost > back to status quo, with nouveau_fence_signal2.0, but with the > dma_fence_is_signaled() part fixed. Well it could potentially be cleaned up more, but as far as I can see only the two lines I pointed out in the other mail need to move at the right place, yes. I mean it's just two lines. If you open code that or if you make a nouveau_cleanup_list_ref() function (or similar) is perfectly up to you. Regards, Christian. > > > P. > >> >> >>> >>> >>> >>>> >>>> Instead the call to dma_fence_signal_locked() should probably be >>>> removed from nouveau_fence_signal() and into >>>> nouveau_fence_context_kill() and nouveau_fence_update(). >>>> >>>> This way nouveau_fence_is_signaled() can call this function as >>>> well. >>>> >>> >>> Which "this function"? dma_fence_signal_locked() >>> >> >> No the cleanup function for the list entry. Whatever you call that >> then, the name nouveau_fence_signal() is probably not appropriate any >> more. >> >> >>> >>> >>> >>>> >>>> BTW: nouveau_fence_no_signaling() looks completely broken as >>>> well. It >>>> calls nouveau_fence_is_signaled() and then list_del() on the >>>> fence >>>> head. >>>> >>> >>> I can assure you that a great many things in Nouveau look >>> completely >>> broken. >>> >>> The question for us is always the cost-benefit-ratio when fixing >>> bugs. >>> There are fixes that solve the bug with reasonable effort, and >>> there >>> are great reworks towards an ideal state. >>> >> >> I would just simply drop that function. As far as I can see it >> severs no purpose other than doing exactly what the common DMA fence >> code does anyway. >> >> Just one less thing which could fail. >> >> Christian. >> >> >>> >>> >>> P. >>> >>> >>> >>>> >>>> As far as I can see that is completely superfluous and should >>>> probably be dropped. IIRC I once had a patch to clean that up but >>>> it >>>> was dropped for some reason. >>>> >>>> Regards, >>>> Christian. >>>> >>>> >>>> >>>>> >>>>> + dma_fence_put(&fence->base); >>>>> + if (ret) >>>>> + return ret; >>>>> + >>>>> ret = fctx->emit(fence); >>>>> if (!ret) { >>>>> dma_fence_get(&fence->base); >>>>> @@ -246,8 +251,7 @@ nouveau_fence_emit(struct nouveau_fence >>>>> *fence) >>>>> return -ENODEV; >>>>> } >>>>> >>>>> - if (nouveau_fence_update(chan, fctx)) >>>>> - nvif_event_block(&fctx->event); >>>>> + nouveau_fence_update(chan, fctx); >>>>> >>>>> list_add_tail(&fence->head, &fctx->pending); >>>>> spin_unlock_irq(&fctx->lock); >>>>> @@ -270,8 +274,8 @@ nouveau_fence_done(struct nouveau_fence >>>>> *fence) >>>>> >>>>> spin_lock_irqsave(&fctx->lock, flags); >>>>> chan = rcu_dereference_protected(fence- >>>>>> channel, >>>>> lockdep_is_held(&fctx->lock)); >>>>> - if (chan && nouveau_fence_update(chan, fctx)) >>>>> - nvif_event_block(&fctx->event); >>>>> + if (chan) >>>>> + nouveau_fence_update(chan, fctx); >>>>> spin_unlock_irqrestore(&fctx->lock, flags); >>>>> } >>>>> return dma_fence_is_signaled(&fence->base); >>>>> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.h >>>>> b/drivers/gpu/drm/nouveau/nouveau_fence.h >>>>> index 8bc065acfe35..e6b2df7fdc42 100644 >>>>> --- a/drivers/gpu/drm/nouveau/nouveau_fence.h >>>>> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.h >>>>> @@ -10,6 +10,7 @@ struct nouveau_bo; >>>>> >>>>> struct nouveau_fence { >>>>> struct dma_fence base; >>>>> + struct dma_fence_cb cb; >>>>> >>>>> struct list_head head; >>>>> >>>>> >>>> >>> >> >>

7 months

CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is broken, was Re: [RFC PATCH 0/6] Deep talk about folio vmap

by Christoph Hellwig

After the btrfs compressed bio discussion I think the hugetlb changes that skip the tail pages are fundamentally unsafe in the current kernel. That is because the bio_vec representation assumes tail pages do exist, so as soon as you are doing direct I/O that generates a bvec starting beyond the present head page things will blow up. Other users of bio_vecs might do the same, but the way the block bio_vecs are generated are very suspect to that. So we'll first need to sort that out and a few other things before we can even think of enabling such a feature.

7 months

[PATCH] dma-buf/sw_sync: Decrement refcount on error in sw_sync_ioctl_get_deadline()

by Dan Carpenter

Call dma_fence_put(fence) before returning an error on this error path. Fixes: 70e67aaec2f4 ("dma-buf/sw_sync: Add fence deadline support") Signed-off-by: Dan Carpenter <dan.carpenter(a)linaro.org> --- drivers/dma-buf/sw_sync.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c index f5905d67dedb..b7615c5c6cac 100644 --- a/drivers/dma-buf/sw_sync.c +++ b/drivers/dma-buf/sw_sync.c @@ -438,8 +438,10 @@ static int sw_sync_ioctl_get_deadline(struct sync_timeline *obj, unsigned long a return -EINVAL; pt = dma_fence_to_sync_pt(fence); - if (!pt) + if (!pt) { + dma_fence_put(fence); return -EINVAL; + } spin_lock_irqsave(fence->lock, flags); if (test_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags)) { -- 2.47.2

7 months

Re: [PATCH v2] drm/nouveau: Prevent signalled fences in pending list

by Christian König

Am 03.04.25 um 15:15 schrieb Danilo Krummrich: > On Thu, Apr 03, 2025 at 02:58:13PM +0200, Philipp Stanner wrote: >> On Thu, 2025-04-03 at 14:08 +0200, Christian König wrote: >>> Am 03.04.25 um 12:13 schrieb Philipp Stanner: >>> BTW: nouveau_fence_no_signaling() looks completely broken as well. It >>> calls nouveau_fence_is_signaled() and then list_del() on the fence >>> head. >> I can assure you that a great many things in Nouveau look completely >> broken. >> >> The question for us is always the cost-benefit-ratio when fixing bugs. >> There are fixes that solve the bug with reasonable effort, and there >> are great reworks towards an ideal state. > That's just an additional thing that Christian noticed. It isn't really directly > related to what you want to fix with your patch. Well there is some relation. From nouveau_fence_no_signaling(): if (nouveau_fence_is_signaled(f)) { list_del(&fence->head); dma_fence_put(&fence->base); return false; } That looks like somebody realized that the fence needs to be removed from the pending list and the reference dropped. It's just that this was added to the wrong function, e.g. those lines need to be in nouveau_fence_is_signaled() and not here. Regards, Christian. > > I think the function can simply be dropped.

7 months, 1 week

Re: [PATCH v2] drm/nouveau: Prevent signalled fences in pending list

by Christian König

Am 03.04.25 um 14:58 schrieb Philipp Stanner: > On Thu, 2025-04-03 at 14:08 +0200, Christian König wrote: >> Am 03.04.25 um 12:13 schrieb Philipp Stanner: >>> Nouveau currently relies on the assumption that dma_fences will >>> only >>> ever get signalled through nouveau_fence_signal(), which takes care >>> of >>> removing a signalled fence from the list >>> nouveau_fence_chan.pending. >>> >>> This self-imposed rule is violated in nouveau_fence_done(), where >>> dma_fence_is_signaled() can signal the fence without removing it >>> from >>> the list. This enables accesses to already signalled fences through >>> the >>> list, which is a bug. >>> >>> Furthermore, it must always be possible to use standard dma_fence >>> methods an a dma_fence and observe valid behavior. The canonical >>> way of >>> ensuring that signalling a fence has additional effects is to add >>> those >>> effects to a callback and register it on that fence. >>> >>> Move the code from nouveau_fence_signal() into a dma_fence >>> callback. >>> Register that callback when creating the fence. >>> >>> Cc: <stable(a)vger.kernel.org> # 4.10+ >>> Signed-off-by: Philipp Stanner <phasta(a)kernel.org> >>> --- >>> Changes in v2: >>> - Remove Fixes: tag. (Danilo) >>> - Remove integer "drop" and call nvif_event_block() in the fence >>> callback. (Danilo) >>> --- >>> drivers/gpu/drm/nouveau/nouveau_fence.c | 52 +++++++++++++-------- >>> ---- >>> drivers/gpu/drm/nouveau/nouveau_fence.h | 1 + >>> 2 files changed, 29 insertions(+), 24 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c >>> b/drivers/gpu/drm/nouveau/nouveau_fence.c >>> index 7cc84472cece..cf510ef9641a 100644 >>> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c >>> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c >>> @@ -50,24 +50,24 @@ nouveau_fctx(struct nouveau_fence *fence) >>> return container_of(fence->base.lock, struct >>> nouveau_fence_chan, lock); >>> } >>> >>> -static int >>> -nouveau_fence_signal(struct nouveau_fence *fence) >>> +static void >>> +nouveau_fence_cleanup_cb(struct dma_fence *dfence, struct >>> dma_fence_cb *cb) >>> { >>> - int drop = 0; >>> + struct nouveau_fence_chan *fctx; >>> + struct nouveau_fence *fence; >>> + >>> + fence = container_of(dfence, struct nouveau_fence, base); >>> + fctx = nouveau_fctx(fence); >>> >>> - dma_fence_signal_locked(&fence->base); >>> list_del(&fence->head); >>> rcu_assign_pointer(fence->channel, NULL); >>> >>> if (test_bit(DMA_FENCE_FLAG_USER_BITS, &fence- >>>> base.flags)) { >>> - struct nouveau_fence_chan *fctx = >>> nouveau_fctx(fence); >>> - >>> if (!--fctx->notify_ref) >>> - drop = 1; >>> + nvif_event_block(&fctx->event); >>> } >>> >>> dma_fence_put(&fence->base); >>> - return drop; >>> } >>> >>> static struct nouveau_fence * >>> @@ -93,8 +93,7 @@ nouveau_fence_context_kill(struct >>> nouveau_fence_chan *fctx, int error) >>> if (error) >>> dma_fence_set_error(&fence->base, error); >>> >>> - if (nouveau_fence_signal(fence)) >>> - nvif_event_block(&fctx->event); >>> + dma_fence_signal_locked(&fence->base); >>> } >>> fctx->killed = 1; >>> spin_unlock_irqrestore(&fctx->lock, flags); >>> @@ -127,11 +126,10 @@ nouveau_fence_context_free(struct >>> nouveau_fence_chan *fctx) >>> kref_put(&fctx->fence_ref, nouveau_fence_context_put); >>> } >>> >>> -static int >>> +static void >>> nouveau_fence_update(struct nouveau_channel *chan, struct >>> nouveau_fence_chan *fctx) >>> { >>> struct nouveau_fence *fence; >>> - int drop = 0; >>> u32 seq = fctx->read(chan); >>> >>> while (!list_empty(&fctx->pending)) { >>> @@ -140,10 +138,8 @@ nouveau_fence_update(struct nouveau_channel >>> *chan, struct nouveau_fence_chan *fc >>> if ((int)(seq - fence->base.seqno) < 0) >>> break; >>> >>> - drop |= nouveau_fence_signal(fence); >>> + dma_fence_signal_locked(&fence->base); >>> } >>> - >>> - return drop; >>> } >>> >>> static void >>> @@ -152,7 +148,6 @@ nouveau_fence_uevent_work(struct work_struct >>> *work) >>> struct nouveau_fence_chan *fctx = container_of(work, >>> struct nouveau_fence_chan, >>> >>> uevent_work); >>> unsigned long flags; >>> - int drop = 0; >>> >>> spin_lock_irqsave(&fctx->lock, flags); >>> if (!list_empty(&fctx->pending)) { >>> @@ -161,11 +156,8 @@ nouveau_fence_uevent_work(struct work_struct >>> *work) >>> >>> fence = list_entry(fctx->pending.next, >>> typeof(*fence), head); >>> chan = rcu_dereference_protected(fence->channel, >>> lockdep_is_held(&fctx->lock)); >>> - if (nouveau_fence_update(chan, fctx)) >>> - drop = 1; >>> + nouveau_fence_update(chan, fctx); >>> } >>> - if (drop) >>> - nvif_event_block(&fctx->event); >>> >>> spin_unlock_irqrestore(&fctx->lock, flags); >>> } >>> @@ -235,6 +227,19 @@ nouveau_fence_emit(struct nouveau_fence >>> *fence) >>> &fctx->lock, fctx->context, ++fctx- >>>> sequence); >>> kref_get(&fctx->fence_ref); >>> >>> + fence->cb.func = nouveau_fence_cleanup_cb; >>> + /* Adding a callback runs into >>> __dma_fence_enable_signaling(), which will >>> + * ultimately run into nouveau_fence_no_signaling(), where >>> a WARN_ON >>> + * would fire because the refcount can be dropped there. >>> + * >>> + * Increment the refcount here temporarily to work around >>> that. >>> + */ >>> + dma_fence_get(&fence->base); >>> + ret = dma_fence_add_callback(&fence->base, &fence->cb, >>> nouveau_fence_cleanup_cb); >> That looks like a really really awkward approach. The driver >> basically uses a the DMA fence infrastructure as middle layer and >> callbacks into itself to cleanup it's own structures. > What else are callbacks good for, if not to do something automatically > when the fence gets signaled? Well if you add a callback for a signal you issued yourself then that's kind of awkward. E.g. you call into the DMA fence code, just for the DMA fence code to call yourself back again. >> Additional to that we don't guarantee any callback order for the DMA >> fence and so it can be that mix cleaning up the callback with other >> work which is certainly not good when you want to guarantee that the >> cleanup happens under the same lock. > Isn't my perception correct that the primary issue you have with this > approach is that dma_fence_put() is called from within the callback? Or > do you also take issue with deleting from the list? Well kind of both. The issue is that the caller of dma_fence_signal() or dma_fence_signal_locked() must hold the reference until the function returns. When you do the list cleanup and the drop inside the callback it is perfectly possible that the fence pointer becomes stale before you return and that's really not a good idea. > >> Instead the call to dma_fence_signal_locked() should probably be >> removed from nouveau_fence_signal() and into >> nouveau_fence_context_kill() and nouveau_fence_update(). >> >> This way nouveau_fence_is_signaled() can call this function as well. > Which "this function"? dma_fence_signal_locked() No the cleanup function for the list entry. Whatever you call that then, the name nouveau_fence_signal() is probably not appropriate any more. > >> BTW: nouveau_fence_no_signaling() looks completely broken as well. It >> calls nouveau_fence_is_signaled() and then list_del() on the fence >> head. > I can assure you that a great many things in Nouveau look completely > broken. > > The question for us is always the cost-benefit-ratio when fixing bugs. > There are fixes that solve the bug with reasonable effort, and there > are great reworks towards an ideal state. I would just simply drop that function. As far as I can see it severs no purpose other than doing exactly what the common DMA fence code does anyway. Just one less thing which could fail. Christian. > > P. > > >> As far as I can see that is completely superfluous and should >> probably be dropped. IIRC I once had a patch to clean that up but it >> was dropped for some reason. >> >> Regards, >> Christian. >> >> >>> + dma_fence_put(&fence->base); >>> + if (ret) >>> + return ret; >>> + >>> ret = fctx->emit(fence); >>> if (!ret) { >>> dma_fence_get(&fence->base); >>> @@ -246,8 +251,7 @@ nouveau_fence_emit(struct nouveau_fence *fence) >>> return -ENODEV; >>> } >>> >>> - if (nouveau_fence_update(chan, fctx)) >>> - nvif_event_block(&fctx->event); >>> + nouveau_fence_update(chan, fctx); >>> >>> list_add_tail(&fence->head, &fctx->pending); >>> spin_unlock_irq(&fctx->lock); >>> @@ -270,8 +274,8 @@ nouveau_fence_done(struct nouveau_fence *fence) >>> >>> spin_lock_irqsave(&fctx->lock, flags); >>> chan = rcu_dereference_protected(fence->channel, >>> lockdep_is_held(&fctx->lock)); >>> - if (chan && nouveau_fence_update(chan, fctx)) >>> - nvif_event_block(&fctx->event); >>> + if (chan) >>> + nouveau_fence_update(chan, fctx); >>> spin_unlock_irqrestore(&fctx->lock, flags); >>> } >>> return dma_fence_is_signaled(&fence->base); >>> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.h >>> b/drivers/gpu/drm/nouveau/nouveau_fence.h >>> index 8bc065acfe35..e6b2df7fdc42 100644 >>> --- a/drivers/gpu/drm/nouveau/nouveau_fence.h >>> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.h >>> @@ -10,6 +10,7 @@ struct nouveau_bo; >>> >>> struct nouveau_fence { >>> struct dma_fence base; >>> + struct dma_fence_cb cb; >>> >>> struct list_head head; >>>

7 months, 1 week

Re: [PATCH v2] drm/nouveau: Prevent signalled fences in pending list

by Christian König

Am 03.04.25 um 12:25 schrieb Danilo Krummrich: > On Thu, Apr 03, 2025 at 12:17:29PM +0200, Philipp Stanner wrote: >> On Thu, 2025-04-03 at 12:13 +0200, Philipp Stanner wrote: >>> -static int >>> -nouveau_fence_signal(struct nouveau_fence *fence) >>> +static void >>> +nouveau_fence_cleanup_cb(struct dma_fence *dfence, struct >>> dma_fence_cb *cb) >>> { >>> - int drop = 0; >>> + struct nouveau_fence_chan *fctx; >>> + struct nouveau_fence *fence; >>> + >>> + fence = container_of(dfence, struct nouveau_fence, base); >>> + fctx = nouveau_fctx(fence); >>> >>> - dma_fence_signal_locked(&fence->base); >>> list_del(&fence->head); >>> rcu_assign_pointer(fence->channel, NULL); >>> >>> if (test_bit(DMA_FENCE_FLAG_USER_BITS, &fence->base.flags)) >>> { >>> - struct nouveau_fence_chan *fctx = >>> nouveau_fctx(fence); >>> - >>> if (!--fctx->notify_ref) >>> - drop = 1; >>> + nvif_event_block(&fctx->event); >>> } >>> >>> dma_fence_put(&fence->base); >> What I realized while coding this v2 is that we might want to think >> about whether we really want the dma_fence_put() in the fence callback? >> >> It should work fine, since it's exactly identical to the previous >> code's behavior – but effectively it means that the driver's reference >> will be dropped whenever it signals that fence. > Not quite, it's the reference of the fence context's pending list. > > When the fence is emitted, dma_fence_init() is called, which initializes the > reference count to 1. Subsequently, another reference is taken, when the fence > is added to the pending list. Once the fence is signaled and hence removed from > the pending list, we can (and have to) drop this reference. The general idea is that the caller must hold the reference until the signaling is completed. So for signaling from the interrupt handler it means that you need to call dma_fence_put() for the list reference *after* you called dma_fence_signal_locked(). For signaling from the .enable_signaling or .signaled callback you need to remove the fence from the linked list and call dma_fence_put() *before* you return (because the caller is holding the potential last reference). That's why I'm pretty sure that the approach with installing the callback won't work. As far as I know no other DMA fence implementation is doing that. Regards, Christian.

7 months, 1 week

Re: [PATCH v2] drm/nouveau: Prevent signalled fences in pending list

by Christian König

Am 03.04.25 um 12:13 schrieb Philipp Stanner: > Nouveau currently relies on the assumption that dma_fences will only > ever get signalled through nouveau_fence_signal(), which takes care of > removing a signalled fence from the list nouveau_fence_chan.pending. > > This self-imposed rule is violated in nouveau_fence_done(), where > dma_fence_is_signaled() can signal the fence without removing it from > the list. This enables accesses to already signalled fences through the > list, which is a bug. > > Furthermore, it must always be possible to use standard dma_fence > methods an a dma_fence and observe valid behavior. The canonical way of > ensuring that signalling a fence has additional effects is to add those > effects to a callback and register it on that fence. > > Move the code from nouveau_fence_signal() into a dma_fence callback. > Register that callback when creating the fence. > > Cc: <stable(a)vger.kernel.org> # 4.10+ > Signed-off-by: Philipp Stanner <phasta(a)kernel.org> > --- > Changes in v2: > - Remove Fixes: tag. (Danilo) > - Remove integer "drop" and call nvif_event_block() in the fence > callback. (Danilo) > --- > drivers/gpu/drm/nouveau/nouveau_fence.c | 52 +++++++++++++------------ > drivers/gpu/drm/nouveau/nouveau_fence.h | 1 + > 2 files changed, 29 insertions(+), 24 deletions(-) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c > index 7cc84472cece..cf510ef9641a 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_fence.c > +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c > @@ -50,24 +50,24 @@ nouveau_fctx(struct nouveau_fence *fence) > return container_of(fence->base.lock, struct nouveau_fence_chan, lock); > } > > -static int > -nouveau_fence_signal(struct nouveau_fence *fence) > +static void > +nouveau_fence_cleanup_cb(struct dma_fence *dfence, struct dma_fence_cb *cb) > { > - int drop = 0; > + struct nouveau_fence_chan *fctx; > + struct nouveau_fence *fence; > + > + fence = container_of(dfence, struct nouveau_fence, base); > + fctx = nouveau_fctx(fence); > > - dma_fence_signal_locked(&fence->base); > list_del(&fence->head); > rcu_assign_pointer(fence->channel, NULL); > > if (test_bit(DMA_FENCE_FLAG_USER_BITS, &fence->base.flags)) { > - struct nouveau_fence_chan *fctx = nouveau_fctx(fence); > - > if (!--fctx->notify_ref) > - drop = 1; > + nvif_event_block(&fctx->event); > } > > dma_fence_put(&fence->base); > - return drop; > } > > static struct nouveau_fence * > @@ -93,8 +93,7 @@ nouveau_fence_context_kill(struct nouveau_fence_chan *fctx, int error) > if (error) > dma_fence_set_error(&fence->base, error); > > - if (nouveau_fence_signal(fence)) > - nvif_event_block(&fctx->event); > + dma_fence_signal_locked(&fence->base); > } > fctx->killed = 1; > spin_unlock_irqrestore(&fctx->lock, flags); > @@ -127,11 +126,10 @@ nouveau_fence_context_free(struct nouveau_fence_chan *fctx) > kref_put(&fctx->fence_ref, nouveau_fence_context_put); > } > > -static int > +static void > nouveau_fence_update(struct nouveau_channel *chan, struct nouveau_fence_chan *fctx) > { > struct nouveau_fence *fence; > - int drop = 0; > u32 seq = fctx->read(chan); > > while (!list_empty(&fctx->pending)) { > @@ -140,10 +138,8 @@ nouveau_fence_update(struct nouveau_channel *chan, struct nouveau_fence_chan *fc > if ((int)(seq - fence->base.seqno) < 0) > break; > > - drop |= nouveau_fence_signal(fence); > + dma_fence_signal_locked(&fence->base); > } > - > - return drop; > } > > static void > @@ -152,7 +148,6 @@ nouveau_fence_uevent_work(struct work_struct *work) > struct nouveau_fence_chan *fctx = container_of(work, struct nouveau_fence_chan, > uevent_work); > unsigned long flags; > - int drop = 0; > > spin_lock_irqsave(&fctx->lock, flags); > if (!list_empty(&fctx->pending)) { > @@ -161,11 +156,8 @@ nouveau_fence_uevent_work(struct work_struct *work) > > fence = list_entry(fctx->pending.next, typeof(*fence), head); > chan = rcu_dereference_protected(fence->channel, lockdep_is_held(&fctx->lock)); > - if (nouveau_fence_update(chan, fctx)) > - drop = 1; > + nouveau_fence_update(chan, fctx); > } > - if (drop) > - nvif_event_block(&fctx->event); > > spin_unlock_irqrestore(&fctx->lock, flags); > } > @@ -235,6 +227,19 @@ nouveau_fence_emit(struct nouveau_fence *fence) > &fctx->lock, fctx->context, ++fctx->sequence); > kref_get(&fctx->fence_ref); > > + fence->cb.func = nouveau_fence_cleanup_cb; > + /* Adding a callback runs into __dma_fence_enable_signaling(), which will > + * ultimately run into nouveau_fence_no_signaling(), where a WARN_ON > + * would fire because the refcount can be dropped there. > + * > + * Increment the refcount here temporarily to work around that. > + */ > + dma_fence_get(&fence->base); > + ret = dma_fence_add_callback(&fence->base, &fence->cb, nouveau_fence_cleanup_cb); That looks like a really really awkward approach. The driver basically uses a the DMA fence infrastructure as middle layer and callbacks into itself to cleanup it's own structures. Additional to that we don't guarantee any callback order for the DMA fence and so it can be that mix cleaning up the callback with other work which is certainly not good when you want to guarantee that the cleanup happens under the same lock. Instead the call to dma_fence_signal_locked() should probably be removed from nouveau_fence_signal() and into nouveau_fence_context_kill() and nouveau_fence_update(). This way nouveau_fence_is_signaled() can call this function as well. BTW: nouveau_fence_no_signaling() looks completely broken as well. It calls nouveau_fence_is_signaled() and then list_del() on the fence head. As far as I can see that is completely superfluous and should probably be dropped. IIRC I once had a patch to clean that up but it was dropped for some reason. Regards, Christian. > + dma_fence_put(&fence->base); > + if (ret) > + return ret; > + > ret = fctx->emit(fence); > if (!ret) { > dma_fence_get(&fence->base); > @@ -246,8 +251,7 @@ nouveau_fence_emit(struct nouveau_fence *fence) > return -ENODEV; > } > > - if (nouveau_fence_update(chan, fctx)) > - nvif_event_block(&fctx->event); > + nouveau_fence_update(chan, fctx); > > list_add_tail(&fence->head, &fctx->pending); > spin_unlock_irq(&fctx->lock); > @@ -270,8 +274,8 @@ nouveau_fence_done(struct nouveau_fence *fence) > > spin_lock_irqsave(&fctx->lock, flags); > chan = rcu_dereference_protected(fence->channel, lockdep_is_held(&fctx->lock)); > - if (chan && nouveau_fence_update(chan, fctx)) > - nvif_event_block(&fctx->event); > + if (chan) > + nouveau_fence_update(chan, fctx); > spin_unlock_irqrestore(&fctx->lock, flags); > } > return dma_fence_is_signaled(&fence->base); > diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.h b/drivers/gpu/drm/nouveau/nouveau_fence.h > index 8bc065acfe35..e6b2df7fdc42 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_fence.h > +++ b/drivers/gpu/drm/nouveau/nouveau_fence.h > @@ -10,6 +10,7 @@ struct nouveau_bo; > > struct nouveau_fence { > struct dma_fence base; > + struct dma_fence_cb cb; > > struct list_head head; >

7 months, 1 week

[PATCH v2 0/2] dma-buf: heaps: Support carved-out heaps

by Maxime Ripard

Hi, This series is the follow-up of the discussion that John and I had some time ago here: https://lore.kernel.org/all/CANDhNCquJn6bH3KxKf65BWiTYLVqSd9892-xtFDHHqqyrr… The initial problem we were discussing was that I'm currently working on a platform which has a memory layout with ECC enabled. However, enabling the ECC has a number of drawbacks on that platform: lower performance, increased memory usage, etc. So for things like framebuffers, the trade-off isn't great and thus there's a memory region with ECC disabled to allocate from for such use cases. After a suggestion from John, I chose to first start using heap allocations flags to allow for userspace to ask for a particular ECC setup. This is then backed by a new heap type that runs from reserved memory chunks flagged as such, and the existing DT properties to specify the ECC properties. After further discussion, it was considered that flags were not the right solution, and relying on the names of the heaps would be enough to let userspace know the kind of buffer it deals with. Thus, even though the uAPI part of it has been dropped in this second version, we still need a driver to create heaps out of carved-out memory regions. In addition to the original usecase, a similar driver can be found in BSPs from most vendors, so I believe it would be a useful addition to the kernel. I submitted a draft PR to the DT schema for the bindings used in this PR: https://github.com/devicetree-org/dt-schema/pull/138 Let me know what you think, Maxime Signed-off-by: Maxime Ripard <mripard(a)kernel.org> --- Changes in v2: - Add vmap/vunmap operations - Drop ECC flags uapi - Rebase on top of 6.14 - Link to v1: https://lore.kernel.org/r/20240515-dma-buf-ecc-heap-v1-0-54cbbd049511@kerne… --- Maxime Ripard (2): dma-buf: heaps: system: Remove global variable dma-buf: heaps: Introduce a new heap for reserved memory drivers/dma-buf/heaps/Kconfig | 8 + drivers/dma-buf/heaps/Makefile | 1 + drivers/dma-buf/heaps/carveout_heap.c | 360 ++++++++++++++++++++++++++++++++++ drivers/dma-buf/heaps/system_heap.c | 17 +- 4 files changed, 381 insertions(+), 5 deletions(-) --- base-commit: fcbf30774e82a441890b722bf0c26542fb82150f change-id: 20240515-dma-buf-ecc-heap-28a311d2c94e Best regards, -- Maxime Ripard <mripard(a)kernel.org>

7 months, 1 week

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