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[PATCH RFC 0/5] memcg: dma-buf per-cgroup accounting via pid_fd

by Albert Esteve

This RFC builds on T.J. Mercier's earlier series [1] which added a memory.stat counter for exported dma-bufs and a binder-backed mechanism to transfer charges between cgroups. The first commit is taken almost verbatim from TJ's series: it introduces MEMCG_DMABUF as a dedicated per-cgroup stat, so that the total exported dma-buf footprint is visible both system-wide (via the root cgroup) and per-application (via per-process cgroups). This avoids the overhead of DMABUF_SYSFS_STATS and integrates naturally into the existing cgroup memory hierarchy. The rest of the series departs from TJ's approach. While the first commit introduces the memcg stat infrastructure for dmabufs, the export-time charging it introduces in dma_buf_export() is then superseded: we charge at dma_heap_ioctl_allocate() time, using a new charge_pid_fd field in struct dma_heap_allocation_data. The allocator opens a pidfd for its client (e.g., from binder's sender_pid), passes it to the ioctl, and the kernel charges the buffer directly to the client's cgroup at allocation time, so no transfer step is needed. This decouples the accounting path from binder entirely: any allocator that knows its client's PID can use the pid_fd mechanism regardless of the IPC transport in use. The cross-cgroup charging capability requires access control. Patches #3 and #4 add a generic LSM hook (security_dma_heap_alloc) and an SELinux implementation based on a new dma_heap object class with a charge_to permission, so policy authors can express which domains are allowed to charge memory to another domain's cgroup. Last patch adds some tests to verify the new charge_pid_fd field. We are sending it as an RFC to spark broader discussion. It may or may not be the right path forward, and we welcome feedback on the trade-offs. Collision note: Eric Chanudet's series [2] adds __GFP_ACCOUNT to system_heap page allocations as an opt-in module parameter. That approach charges pages to the allocator's own kmem, which overlaps with MEMCG_DMABUF. This series explicitly removes __GFP_ACCOUNT from system heap allocations and routes all accounting through the MEMCG_DMABUF path to avoid double-counting. [1] https://lore.kernel.org/cgroups/20230109213809.418135-1-tjmercier@google.co… [2] https://lore.kernel.org/r/20260113-dmabuf-heap-system-memcg-v2-0-e85722cc2f… Signed-off-by: Albert Esteve <aesteve(a)redhat.com> --- Albert Esteve (4): dma-heap: charge dma-buf memory via explicit memcg security: dma-heap: Add dma_heap_alloc LSM hook selinux: Restrict cross-cgroup dma-heap charging selftests/dmabuf-heaps: Add dma-buf memcg accounting tests T.J. Mercier (1): memcg: Track exported dma-buffers Documentation/admin-guide/cgroup-v2.rst | 5 + drivers/dma-buf/dma-buf.c | 7 + drivers/dma-buf/dma-heap.c | 54 +++++- drivers/dma-buf/heaps/system_heap.c | 2 - include/linux/dma-buf.h | 4 + include/linux/lsm_hook_defs.h | 1 + include/linux/memcontrol.h | 37 ++++ include/linux/security.h | 7 + include/uapi/linux/dma-heap.h | 6 + mm/memcontrol.c | 19 ++ security/security.c | 16 ++ security/selinux/hooks.c | 7 + security/selinux/include/classmap.h | 1 + tools/testing/selftests/cgroup/Makefile | 2 +- tools/testing/selftests/cgroup/test_memcontrol.c | 143 +++++++++++++- tools/testing/selftests/dmabuf-heaps/config | 1 + tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c | 126 ++++++++++++- tools/testing/selftests/dmabuf-heaps/vmtest.sh | 205 +++++++++++++++++++++ 18 files changed, 633 insertions(+), 10 deletions(-) --- base-commit: 74fe02ce122a6103f207d29fafc8b3a53de6abaf change-id: 20260508-v2_20230123_tjmercier_google_com-f44fcfb16530 Best regards, -- Albert Esteve <aesteve(a)redhat.com>

4 hours, 41 minutes

Re: [PATCH 4/8] drm/panthor: Add support for protected memory allocation in panthor

by Liviu Dudau

On Tue, May 12, 2026 at 04:11:11PM +0200, Boris Brezillon wrote: > On Tue, 12 May 2026 14:47:27 +0100 > Liviu Dudau <liviu.dudau(a)arm.com> wrote: > > > On Thu, May 07, 2026 at 01:53:56PM +0200, Boris Brezillon wrote: > > > On Thu, 7 May 2026 11:02:26 +0200 > > > Marcin Ślusarz <marcin.slusarz(a)arm.com> wrote: > > > > > > > On Tue, May 05, 2026 at 06:15:23PM +0200, Boris Brezillon wrote: > > > > > > @@ -277,9 +286,21 @@ int panthor_device_init(struct panthor_device *ptdev) > > > > > > return ret; > > > > > > } > > > > > > > > > > > > + /* If a protected heap name is specified but not found, defer the probe until created */ > > > > > > + if (protected_heap_name && strlen(protected_heap_name)) { > > > > > > > > > > Do we really need this strlen() > 0? Won't dma_heap_find() fail is the > > > > > name is "" already? > > > > > > > > If dma_heap_find() will fail, then the whole probe with fail too. > > > > This check prevents that. > > > > > > Yeah, that's also a questionable design choice. I mean, we can > > > currently probe and boot the FW even though we never setup the > > > protected FW sections, so why should we defer the probe here? Can't we > > > just retry the next time a group with the protected bit is created and > > > fail if we can find a protected heap? > > > > The problem we have with the current firmware is that it does a number of setup steps at "boot" > > time only. One of the steps is preparing its internal structures for when it enters protected > > mode and it stores them in the buffer passed in at firmware loading. We cannot later run the > > process when we have a group with protected mode set. > > No, but we can force a full/slow reset and have that thing > re-initialized, can't we? I mean, that's basically what we do when a > fast reset fails: we re-initialize all the sections and reset again, at > which point the FW should start from a fresh state, and be able to > properly initialize the protected-related stuff if protected sections > are populated. Am I missing something? Right, we can do that. For some reason I keep associating the reset with the error handling and not with "normal" operations. Best regards, Liviu -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯

7 hours, 56 minutes

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8 hours, 33 minutes

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by Jamestoah113＠gmail.com

8 hours, 33 minutes

Re: [PATCH 4/8] drm/panthor: Add support for protected memory allocation in panthor

by Liviu Dudau

On Thu, May 07, 2026 at 01:53:56PM +0200, Boris Brezillon wrote: > On Thu, 7 May 2026 11:02:26 +0200 > Marcin Ślusarz <marcin.slusarz(a)arm.com> wrote: > > > On Tue, May 05, 2026 at 06:15:23PM +0200, Boris Brezillon wrote: > > > > @@ -277,9 +286,21 @@ int panthor_device_init(struct panthor_device *ptdev) > > > > return ret; > > > > } > > > > > > > > + /* If a protected heap name is specified but not found, defer the probe until created */ > > > > + if (protected_heap_name && strlen(protected_heap_name)) { > > > > > > Do we really need this strlen() > 0? Won't dma_heap_find() fail is the > > > name is "" already? > > > > If dma_heap_find() will fail, then the whole probe with fail too. > > This check prevents that. > > Yeah, that's also a questionable design choice. I mean, we can > currently probe and boot the FW even though we never setup the > protected FW sections, so why should we defer the probe here? Can't we > just retry the next time a group with the protected bit is created and > fail if we can find a protected heap? The problem we have with the current firmware is that it does a number of setup steps at "boot" time only. One of the steps is preparing its internal structures for when it enters protected mode and it stores them in the buffer passed in at firmware loading. We cannot later run the process when we have a group with protected mode set. So unfortunately adding support for protected mode where the heap name is provided means we have to try our best to set it up at boot time, or otherwise disable protected mode support. Best regards, Liviu > > > I'm not sure why it's needed at all, but if > > it is really needed, then s/strlen(protected_heap_name)/protected_heap_name[0]/ > > would simplify this. > > It's not so much about how you do the test, and more about the case > you're trying to protect against. I guess here you assume that > panthor.protected_heap_name="" means "I don't have a protected heap for > you". If it's deemed acceptable, this should most certainly be > described somewhere. > > > > > > > + ptdev->protm.heap = dma_heap_find(protected_heap_name); > > > > + if (!ptdev->protm.heap) { > > > > + drm_warn(&ptdev->base, > > > > + "Protected heap \'%s\' not (yet) available - deferring probe", > > > > + protected_heap_name); > > > > + ret = -EPROBE_DEFER; > > > > + goto err_rpm_put; > > > > > > If you move the heap retrieval before the rpm enablement, you can get > > > rid of this goto err_rpm_put. > > > > > > > + } > > > > + } > > > > + > > > > ret = panthor_hw_init(ptdev); > > > > if (ret) > > > > - goto err_rpm_put; > > > > + goto err_dma_heap_put; > > > > > > > > ret = panthor_pwr_init(ptdev); > > > > if (ret) > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯

9 hours, 47 minutes

Re: [PATCH 3/8] drm/panthor: De-duplicate FW memory section sync

by Liviu Dudau

On Tue, May 05, 2026 at 04:05:09PM +0200, Ketil Johnsen wrote: > Handle the sync to device of FW memory sections inside > panthor_fw_init_section_mem() so that the callers do not have to. > > This small improvement is also critical for protected FW sections, > so we avoid issuing memory transactions to protected memory from > CPU running in normal mode. > > Signed-off-by: Ketil Johnsen <ketil.johnsen(a)arm.com> Reviewed-by: Liviu Dudau <liviu.dudau(a)arm.com> Best regards, Liviu > --- > drivers/gpu/drm/panthor/panthor_fw.c | 22 ++++++---------------- > 1 file changed, 6 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c > index be0da5b1f3abf..0d07a133dc3af 100644 > --- a/drivers/gpu/drm/panthor/panthor_fw.c > +++ b/drivers/gpu/drm/panthor/panthor_fw.c > @@ -446,6 +446,7 @@ static void panthor_fw_init_section_mem(struct panthor_device *ptdev, > struct panthor_fw_section *section) > { > bool was_mapped = !!section->mem->kmap; > + struct sg_table *sgt; > int ret; > > if (!section->data.size && > @@ -464,6 +465,11 @@ static void panthor_fw_init_section_mem(struct panthor_device *ptdev, > > if (!was_mapped) > panthor_kernel_bo_vunmap(section->mem); > + > + /* An sgt should have been requested when the kernel BO was GPU-mapped. */ > + sgt = to_panthor_bo(section->mem->obj)->dmap.sgt; > + if (!drm_WARN_ON_ONCE(&ptdev->base, !sgt)) > + dma_sync_sgtable_for_device(ptdev->base.dev, sgt, DMA_TO_DEVICE); > } > > /** > @@ -626,7 +632,6 @@ static int panthor_fw_load_section_entry(struct panthor_device *ptdev, > section_size = hdr.va.end - hdr.va.start; > if (section_size) { > u32 cache_mode = hdr.flags & CSF_FW_BINARY_IFACE_ENTRY_CACHE_MODE_MASK; > - struct panthor_gem_object *bo; > u32 vm_map_flags = 0; > u64 va = hdr.va.start; > > @@ -663,14 +668,6 @@ static int panthor_fw_load_section_entry(struct panthor_device *ptdev, > } > > panthor_fw_init_section_mem(ptdev, section); > - > - bo = to_panthor_bo(section->mem->obj); > - > - /* An sgt should have been requested when the kernel BO was GPU-mapped. */ > - if (drm_WARN_ON_ONCE(&ptdev->base, !bo->dmap.sgt)) > - return -EINVAL; > - > - dma_sync_sgtable_for_device(ptdev->base.dev, bo->dmap.sgt, DMA_TO_DEVICE); > } > > if (hdr.va.start == CSF_MCU_SHARED_REGION_START) > @@ -724,17 +721,10 @@ panthor_reload_fw_sections(struct panthor_device *ptdev, bool full_reload) > struct panthor_fw_section *section; > > list_for_each_entry(section, &ptdev->fw->sections, node) { > - struct sg_table *sgt; > - > if (!full_reload && !(section->flags & CSF_FW_BINARY_IFACE_ENTRY_WR)) > continue; > > panthor_fw_init_section_mem(ptdev, section); > - > - /* An sgt should have been requested when the kernel BO was GPU-mapped. */ > - sgt = to_panthor_bo(section->mem->obj)->dmap.sgt; > - if (!drm_WARN_ON_ONCE(&ptdev->base, !sgt)) > - dma_sync_sgtable_for_device(ptdev->base.dev, sgt, DMA_TO_DEVICE); > } > } > > -- > 2.43.0 > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯

9 hours, 57 minutes

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by cold.puma.etfk＠hidingmail.net

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15 hours, 7 minutes

Re: [PATCH v3 00/10] Add dmabuf read/write via io_uring

by Christoph Hellwig

What tree is this against? I can't apply it against the usual candidates, even accounting for the time lag in getting to it. Can you provide a git tree?

16 hours, 34 minutes

Re: [PATCH v2] drm/virtio: move cursor resv lock acquisition to prepare_fb

by Dmitry Osipenko

On 5/12/26 05:07, Deepanshu Kartikey wrote: > virtio_gpu_cursor_plane_update() allocates a virtio_gpu_object_array, > locks its dma_resv, and queues a fenced transfer to the host. The > lock acquisition can fail in two ways: > > - dma_resv_lock_interruptible() returns -EINTR when a signal is > delivered while waiting for the reservation lock. > - dma_resv_reserve_fences() returns -ENOMEM if it fails to allocate > a fence slot; in this case lock_resv unlocks before returning. > > The return value was ignored, so the cursor path could proceed with > the resv lock not held. The queue path then walks the object array > and calls dma_resv_add_fence(), which requires the lock; with lockdep > enabled this trips dma_resv_assert_held(): > > WARNING: drivers/dma-buf/dma-resv.c:296 at dma_resv_add_fence+0x71e/0x840 > Call Trace: > virtio_gpu_array_add_fence > virtio_gpu_queue_ctrl_sgs > virtio_gpu_queue_fenced_ctrl_buffer > virtio_gpu_cursor_plane_update > drm_atomic_helper_commit_planes > drm_atomic_helper_commit_tail > commit_tail > drm_atomic_helper_commit > drm_atomic_commit > drm_atomic_helper_update_plane > __setplane_atomic > drm_mode_cursor_universal > drm_mode_cursor_common > drm_mode_cursor_ioctl > drm_ioctl > __x64_sys_ioctl > > Beyond the WARN, mutating the dma_resv fence list without the lock > races with concurrent readers/writers and can corrupt the list. > > The DRM atomic helpers do not allow .atomic_update to fail: by the > time it runs, the commit has been signed off to userspace and there > is no clean rollback path. Move the fallible work -- objs allocation, > dma_resv locking, and fence slot reservation -- into > virtio_gpu_plane_prepare_fb, which is the designated callback for > resource acquisition and may return errors that the framework > handles by rolling back the commit. Stash the prepared object array > on virtio_gpu_plane_state so the update step can consume it. > > Make virtio_gpu_plane_cleanup_fb release the objs if the commit was > rolled back before update ran (i.e., objs not consumed). The queue > path already unlocks the resv after attaching the fence (vq.c:411) > and frees the array via put_free_delayed after host completion > (vq.c:271), so the update step only needs to clear vgplane_st->objs > to transfer ownership. > > Simplify virtio_gpu_cursor_plane_update to a no-fail queue submission > that hands the prepared, locked objs to the queue path. > > The bug was reported by syzbot, triggered via fault injection > (fail_nth) on the DRM_IOCTL_MODE_CURSOR path, which forces the > -ENOMEM branch in dma_resv_reserve_fences(). > > Reported-by: syzbot+72bd3dd3a5d5f39a0271(a)syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=72bd3dd3a5d5f39a0271 > Fixes: 5cfd31c5b3a3 ("drm/virtio: fix virtio_gpu_cursor_plane_update().") > Cc: stable(a)vger.kernel.org > Link: https://lore.kernel.org/all/20260510053025.100224-1-kartikey406@gmail.com/T/ [v1] > Signed-off-by: Deepanshu Kartikey <kartikey406(a)gmail.com> > --- > v2: Move resv lock acquisition from .atomic_update (which must not > fail) to .prepare_fb (which may), per maintainer review of v1. > The previous approach of silently skipping the cursor update on > lock failure violated the atomic-commit contract with userspace. > --- > drivers/gpu/drm/virtio/virtgpu_drv.h | 1 + > drivers/gpu/drm/virtio/virtgpu_plane.c | 38 ++++++++++++++++++++------ > 2 files changed, 30 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h > index f17660a71a3e..e51f959dce46 100644 > --- a/drivers/gpu/drm/virtio/virtgpu_drv.h > +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h > @@ -198,6 +198,7 @@ struct virtio_gpu_framebuffer { > struct virtio_gpu_plane_state { > struct drm_plane_state base; > struct virtio_gpu_fence *fence; > + struct virtio_gpu_object_array *objs; > }; > #define to_virtio_gpu_plane_state(x) \ > container_of(x, struct virtio_gpu_plane_state, base) > diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c > index a126d1b25f46..b0511ace89e6 100644 > --- a/drivers/gpu/drm/virtio/virtgpu_plane.c > +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c > @@ -381,6 +381,23 @@ static int virtio_gpu_plane_prepare_fb(struct drm_plane *plane, > goto err_fence; > } > > + if (plane->type == DRM_PLANE_TYPE_CURSOR && bo->dumb) { > + struct virtio_gpu_object_array *objs; > + > + objs = virtio_gpu_array_alloc(1); > + if (!objs) { > + ret = -ENOMEM; > + goto err_fence; > + } > + virtio_gpu_array_add_obj(objs, vgfb->base.obj[0]); > + ret = virtio_gpu_array_lock_resv(objs); > + if (ret) { > + virtio_gpu_array_put_free(objs); > + goto err_fence; > + } > + vgplane_st->objs = objs; > + } > + > return 0; > > err_fence: > @@ -417,6 +434,12 @@ static void virtio_gpu_plane_cleanup_fb(struct drm_plane *plane, > vgplane_st->fence = NULL; > } > > + if (vgplane_st->objs) { > + virtio_gpu_array_unlock_resv(vgplane_st->objs); > + virtio_gpu_array_put_free(vgplane_st->objs); > + vgplane_st->objs = NULL; > + } > + > obj = state->fb->obj[0]; > if (drm_gem_is_imported(obj)) > virtio_gpu_cleanup_imported_obj(obj); > @@ -452,21 +475,18 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane *plane, > } > > if (bo && bo->dumb && (plane->state->fb != old_state->fb)) { > - /* new cursor -- update & wait */ > - struct virtio_gpu_object_array *objs; > - > - objs = virtio_gpu_array_alloc(1); > - if (!objs) > - return; > - virtio_gpu_array_add_obj(objs, vgfb->base.obj[0]); > - virtio_gpu_array_lock_resv(objs); > + /* objs and fence were prepared in virtio_gpu_plane_prepare_fb; > + * the resv is already locked. The queue path takes ownership > + * of objs and unlocks the resv after attaching the fence. > + */ > virtio_gpu_cmd_transfer_to_host_2d > (vgdev, 0, > plane->state->crtc_w, > plane->state->crtc_h, > - 0, 0, objs, vgplane_st->fence); > + 0, 0, vgplane_st->objs, vgplane_st->fence); > virtio_gpu_notify(vgdev); > dma_fence_wait(&vgplane_st->fence->f, true); > + vgplane_st->objs = NULL; > } > > if (plane->state->fb != old_state->fb) { I'm getting lockup with this patch applied and now see that virtio_gpu_resource_flush() also locks BO. Easiest option might be to add uninterruptible variant of virtio_gpu_array_lock_resv(). Could you please try it for v3? -- Best regards, Dmitry

17 hours

Re: [RFC PATCH 04/12] vfio/pci: Allow MMIO regions to be exported through dma-buf

by Jason Gunthorpe

On Tue, May 12, 2026 at 09:42:01AM +1000, Alexey Kardashevskiy wrote: > > true but either way dmabuf slicing will be directed by QEMU's msix-table > > emulation MR and this slicing needs to match the TDISP report so I'll > > have to teach QEMU these reports, right? > > Or TDISP devices are going to align MSIX BARs to 4K, and QEMU will > do the same and it should "just work", and if it does not - the host > won't crash. Can this work? Thanks, Host crashing stuff is a different issue, I think the plan was to revoke the entire MMIO space from userspace and remove it from the kernel mapping. Entire because we don't want to parse the TDISP report to figure out something more narrow. Therefore there is no way the host can crash. When qemu constructs the VM memory map it already has a scheme to insert a hole for a SW emulated page for MSI. That will keep working exactly as it is. When the VM validates the MMIO the hole has to fall within a T=0 space of the TDISP report or the VM will reject it. This means devices need to have a T=0 hole around their MSI-X/etc suitable for a 64K page size OS. This is already the case, if a device mixes MSIx with other things qemu will work but it becomes horribly slow and a little broken. Jason

23 hours, 38 minutes

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