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Re: [RFC PATCH 4/7] dma-buf: uapi: Mechanism to revoke DMABUFs via ioctl()

by Christian König

On 2/26/26 21:22, Matt Evans wrote: > Add a new dma-buf ioctl() op, DMA_BUF_IOCTL_REVOKE, connected to a new > (optional) dma_buf_ops callback, revoke(). An exporter receiving this > will _permanently_ revoke the DMABUF, meaning it can no longer be > mapped/attached/mmap()ed. It also guarantees that existing > importers have been detached (e.g. via move_notify) and all mappings > made inaccessible. > > This is useful for lifecycle management in scenarios where a process > has created a DMABUF representing a resource, then delegated it to > a client process; access to the resource is revoked when the client is > deemed "done", and the resource can be safely re-used elsewhere. Well that means revoking from the importer side. That absolutely doesn't make sense to me. Why would you do that? Regards, Christian. > > Signed-off-by: Matt Evans <mattev(a)meta.com> > --- > drivers/dma-buf/dma-buf.c | 5 +++++ > include/linux/dma-buf.h | 22 ++++++++++++++++++++++ > include/uapi/linux/dma-buf.h | 1 + > 3 files changed, 28 insertions(+) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index edaa9e4ee4ae..b9b315317f2d 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c > @@ -561,6 +561,11 @@ static long dma_buf_ioctl(struct file *file, > case DMA_BUF_IOCTL_IMPORT_SYNC_FILE: > return dma_buf_import_sync_file(dmabuf, (const void __user *)arg); > #endif > + case DMA_BUF_IOCTL_REVOKE: > + if (dmabuf->ops->revoke) > + return dmabuf->ops->revoke(dmabuf); > + else > + return -EINVAL; > > default: > return -ENOTTY; > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > index 0bc492090237..a68c9ad7aebd 100644 > --- a/include/linux/dma-buf.h > +++ b/include/linux/dma-buf.h > @@ -277,6 +277,28 @@ struct dma_buf_ops { > > int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map); > void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map); > + > + /** > + * @revoke: > + * > + * This callback is invoked from a userspace > + * DMA_BUF_IOCTL_REVOKE operation, and requests that access to > + * the buffer is immediately and permanently revoked. On > + * successful return, the buffer is not accessible through any > + * mmap() or dma-buf import. The request fails if the buffer > + * is pinned; otherwise, the exporter marks the buffer as > + * inaccessible and uses the move_notify callback to inform > + * importers of the change. The buffer is permanently > + * disabled, and the exporter must refuse all map, mmap, > + * attach, etc. requests. > + * > + * Returns: > + * > + * 0 on success, or a negative error code on failure: > + * -ENODEV if the associated device no longer exists/is closed. > + * -EBADFD if the buffer has already been revoked. > + */ > + int (*revoke)(struct dma_buf *dmabuf); > }; > > /** > diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h > index 5a6fda66d9ad..84bf2dd2d0f3 100644 > --- a/include/uapi/linux/dma-buf.h > +++ b/include/uapi/linux/dma-buf.h > @@ -178,5 +178,6 @@ struct dma_buf_import_sync_file { > #define DMA_BUF_SET_NAME_B _IOW(DMA_BUF_BASE, 1, __u64) > #define DMA_BUF_IOCTL_EXPORT_SYNC_FILE _IOWR(DMA_BUF_BASE, 2, struct dma_buf_export_sync_file) > #define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW(DMA_BUF_BASE, 3, struct dma_buf_import_sync_file) > +#define DMA_BUF_IOCTL_REVOKE _IO(DMA_BUF_BASE, 4) > > #endif > -- > 2.47.3 >

2 weeks, 3 days

Re: [RFC PATCH 3/7] vfio/pci: Support mmap() of a DMABUF

by Christian König

On 2/26/26 21:21, Matt Evans wrote: > A VFIO DMABUF can export a subset of a BAR to userspace by fd; add > support for mmap() of this fd. This provides another route for a > process to map BARs, except one where the process can only map a specific > subset of a BAR represented by the exported DMABUF. > > mmap() support enables userspace driver designs that safely delegate > access to BAR sub-ranges to other client processes by sharing a DMABUF > fd, without having to share the (omnipotent) VFIO device fd with them. > > The mmap callback installs vm_ops callbacks for .fault and .huge_fault; > they find a PFN by searching the DMABUF's physical ranges. That is, > DMABUFs with multiple ranges are supported for mmap(). In general sounds like a good idea but this approach here doesn't looks good at all. Especially how you call unmap_mapping_range() from your DMA-buf cleanup path looks extremely questionable. ... > +/* > + * Similar to vfio_pci_core_mmap() for a regular VFIO device fd, but > + * differs by pre-checks performed and ultimately the vm_ops installed. > + */ > +static int vfio_pci_dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) > +{ > + struct vfio_pci_dma_buf *priv = dmabuf->priv; > + u64 req_len, req_start; > + > + if (!vfio_pci_dma_buf_is_mappable(dmabuf)) > + return -ENODEV; > + if ((vma->vm_flags & VM_SHARED) == 0) > + return -EINVAL; > + > + req_len = vma->vm_end - vma->vm_start; > + req_start = vma->vm_pgoff << PAGE_SHIFT; > + > + if (req_start + req_len > priv->size) > + return -EINVAL; > + > + vma->vm_private_data = priv; > + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); > + vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot); > + > + /* > + * See comments in vfio_pci_core_mmap() re VM_ALLOW_ANY_UNCACHED. > + * > + * FIXME: get mapping attributes from dmabuf? > + */ > + vm_flags_set(vma, VM_ALLOW_ANY_UNCACHED | VM_IO | VM_PFNMAP | > + VM_DONTEXPAND | VM_DONTDUMP); > + vma->vm_ops = &vfio_pci_dma_buf_mmap_ops; > + > + return 0; Let's start with this here, it just looks horrible over complicated. When a DMA-buf just represents a linear piece of BAR which is map-able through the VFIO FD anyway then the right approach is to just re-direct the mapping to this VFIO FD. Roughly something like this here should do it: vma->vm_pgoff += offset_which_your_dma_buf_represents; vma_set_file(vma, core_dev->file); vfio_pci_core_mmap(core_dev, vma); It can be that you want additional checks (e.g. if the DMA-buf is revoked) in which case you would need to override the vma->vm_ops, but then just do the access checks and call the vfio_pci_mmap_ops to get the actually page fault handling done. >+ unmap_mapping_range(priv->dmabuf->file->f_mapping, >+ 0, priv->size, 1); When you need to use unmap_mapping_range() then you usually share the address space object between the file descriptor exporting the DMA-buf and the DMA-buf fd itself. Otherwise functions like vfio_pci_zap_bars() doesn't work correctly any more and that usually creates a huge bunch of problems. Regards, Christian.

2 weeks, 3 days

Re: [PATCH 3/9] dt-bindings: npu: Add bindings for NXP Neutron

by Conor Dooley

On Fri, Feb 27, 2026 at 08:45:29AM +0200, Daniel Baluta wrote: > On 2/26/26 20:20, Conor Dooley wrote: > [..] > >> + - | > >> + #include <dt-bindings/interrupt-controller/arm-gic.h> > >> + #include <dt-bindings/interrupt-controller/irq.h> > >> + > >> + bus { > >> + #address-cells = <2>; > >> + #size-cells = <2>; > >> + > >> + neutron@4ab00000 { > > "neutron" is not a generic node name. This should be something like > > "accelerator" or similar. > > > The only dts nodes I could find using accel subsystem are from rockhip. And they use npu@ > > e.g: > > » rknn_core_0: npu@fdab0000 { > » » compatible = "rockchip,rk3588-rknn-core"; > > Also, Ethos-U64 introduced by Rob with [1] is using npu@. > > So, I think we should go wit that. I haven't seen any document to standardize the naming. accelerator, npu, makes no difference to me, so sure.

2 weeks, 3 days

Re: [PATCH 3/9] dt-bindings: npu: Add bindings for NXP Neutron

by Krzysztof Kozlowski

On 26/02/2026 14:40, Ioana Ciocoi-Radulescu wrote: A nit, subject: drop second/last, redundant "bindings for". The "dt-bindings" prefix is already stating that these are bindings. See also: https://elixir.bootlin.com/linux/v6.17-rc3/source/Documentation/devicetree/… > + > + memory-region: > + description: > + Phandle referencing a "shared-dma-pool" to be used for Neutron > + inference buffers, which need to be 1MB aligned. > + > + The memory region must be defined with alignment of 1MB and size > + should be large enough to accommodate the targeted ML models. It > + should be marked as reusable. > + maxItems: 1 > + > + interrupts: > + maxItems: 1 > + > + clocks: > + minItems: 2 > + maxItems: 3 Why is this flexible? > + > + clock-names: > + minItems: 2 > + items: > + - const: npu Name "npu" is pretty pointless. > + - const: npu_apb > + - const: npu_cgc Drop npu perfix everywhere. > + > + iommus: > + maxItems: 1 > + > + power-domains: > + maxItems: 1 > + > +required: > + - compatible > + - reg > + - reg-names > + - memory-region > + - interrupts > + > +additionalProperties: false > + > +examples: > + - | > + #include <dt-bindings/interrupt-controller/arm-gic.h> > + #include <dt-bindings/interrupt-controller/irq.h> > + > + bus { > + #address-cells = <2>; > + #size-cells = <2>; > + > + neutron@4ab00000 { > + compatible = "nxp,imx95-neutron"; Messed indentation. Read writing bindings / writing schema. Best regards, Krzysztof

2 weeks, 3 days

TOP 10 BEST CRYPTOCURRENCY RECOVERY SPECIALIST LEGITIMATE CRYPTO FUND RECOVERY SPECIALIST LEADER

by henrylevi287＠gmail.com

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2 weeks, 3 days

TOP 9 BEST CRYPTOCURRENCY RECOVERY AGENCY LEGITIMATE CRYPTO FUND RECOVERY AGENCY LEADER

by henrylevi287＠gmail.com

2 weeks, 3 days

TOP 8 BEST CRYPTOCURRENCY RECOVERY EXPERT LEGITIMATE CRYPTO FUND RECOVERY EXPERT LEADER

by henrylevi287＠gmail.com

2 weeks, 3 days

TOP 7 BEST CRYPTOCURRENCY RECOVERY SERVICE LEGITIMATE CRYPTO FUND RECOVERY SERVICE LEADER

by henrylevi287＠gmail.com

2 weeks, 3 days

TOP 6 BEST CRYPTOCURRENCY RECOVERY COMPANY LEGITIMATE CRYPTO FUND RECOVERY COMPANY LEADER

by henrylevi287＠gmail.com

2 weeks, 3 days

TOP 5 BEST CRYPTOCURRENCY RECOVERY SPECIALIST LEGITIMATE CRYPTO FUND RECOVERY SPECIALIST LEADER

by henrylevi287＠gmail.com

2 weeks, 3 days

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