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Re: [PATCH net-next v3 2/2] dma-buf: heaps: system: add system_cc_decrypted heap for explicitly decrypted memory

by Jason Gunthorpe

On Mon, Mar 09, 2026 at 09:39:44AM -0600, Peter Gonda wrote: > Great feature to have thanks Jiri! A couple naive questions. > > On Thu, Mar 5, 2026 at 5:38 AM Jiri Pirko <jiri(a)resnulli.us> wrote: > > > > From: Jiri Pirko <jiri(a)nvidia.com> > > > > Add a new "system_cc_decrypted" dma-buf heap to allow userspace to > > allocate decrypted (shared) memory for confidential computing (CoCo) > > VMs. > > > > On CoCo VMs, guest memory is encrypted by default. The hardware uses an > > encryption bit in page table entries (C-bit on AMD SEV, "shared" bit on > > Intel TDX) to control whether a given memory access is encrypted or > > decrypted. The kernel's direct map is set up with encryption enabled, > > so pages returned by alloc_pages() are encrypted in the direct map > > by default. To make this memory usable for devices that do not support > > DMA to encrypted memory (no TDISP support), it has to be explicitly > > decrypted. A couple of things are needed to properly handle > > decrypted memory for the dma-buf use case: > > > > - set_memory_decrypted() on the direct map after allocation: > > Besides clearing the encryption bit in the direct map PTEs, this > > also notifies the hypervisor about the page state change. On free, > > the inverse set_memory_encrypted() must be called before returning > > pages to the allocator. If re-encryption fails, pages > > are intentionally leaked to prevent decrypted memory from being > > reused as private. > > > > - pgprot_decrypted() for userspace and kernel virtual mappings: > > Any new mapping of the decrypted pages, be it to userspace via > > mmap or to kernel vmalloc space via vmap, creates PTEs independent > > of the direct map. These must also have the encryption bit cleared, > > otherwise accesses through them would see encrypted (garbage) data. > > So this only works on new mappings? What if there are existing > mappings to the memory that will be converted to shared? The set_memory_decrypted() is called during system_heap_allocate(), it is not possible to change dynamically between encrypted/decrypted. Once the heap is created every PTE is always created with the correct pgprot. Jason

4 weeks

Re: [PATCH net-next v3 1/2] dma-mapping: introduce DMA_ATTR_CC_DECRYPTED for pre-decrypted memory

by Jason Gunthorpe

On Mon, Mar 09, 2026 at 01:56:10PM +0100, Petr Tesarik wrote: > I don't want to start a bikeshedding discussion, so if everyone else > likes this name, let's keep it. But maybe the "_CC" (meaning > Confidential Comptuing) is not necessary. IIUC it's the same concept as > set_page_encrypted(), set_page_decrypted(), which does not refer to > CoCo either. Frankly I hate that AMD got their "encrypted" "decrypted" naming baked into the CC related APIs. I'm not at all convinced that they "do not refer to CoCo" in the way Linux uses them and other arches absolutely make them 100% tied to coco. If we are going to bikeshed the name it should be DMA_ATTR_CC_SHARED Jason

4 weeks

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4 weeks, 1 day

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4 weeks, 1 day

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4 weeks, 1 day

[PATCH v7 0/8] dma-buf: Use revoke mechanism to invalidate shared buffers

by Leon Romanovsky

Changelog: v7: * Fixed messed VFIO patch due to rebase. v6: https://patch.msgid.link/20260130-dmabuf-revoke-v6-0-06278f9b7bf0@nvidia.com * Added Reviewed-by tags. * Changed for blocking wait_for_completion() in VFIO * Fixed race between ->attach and move_notify, where priv->revoked is flipped and lock is released. v5: https://patch.msgid.link/20260124-dmabuf-revoke-v5-0-f98fca917e96@nvidia.com * Documented the DMA-BUF expectations around DMA unmap. * Added wait support in VFIO for DMA unmap. * Reordered patches. * Improved commit messages to document even more. v4: https://lore.kernel.org/all/20260121-dmabuf-revoke-v4-0-d311cbc8633d@nvidia… * Changed DMA_RESV_USAGE_KERNEL to DMA_RESV_USAGE_BOOKKEEP. * Made .invalidate_mapping() truly optional. * Added patch which renames dma_buf_move_notify() to be dma_buf_invalidate_mappings(). * Restored dma_buf_attachment_is_dynamic() function. v3: https://lore.kernel.org/all/20260120-dmabuf-revoke-v3-0-b7e0b07b8214@nvidia… * Used Jason's wordings for commits and cover letter. * Removed IOMMUFD patch. * Renamed dma_buf_attachment_is_revoke() to be dma_buf_attach_revocable(). * Added patch to remove CONFIG_DMABUF_MOVE_NOTIFY. * Added Reviewed-by tags. * Called to dma_resv_wait_timeout() after dma_buf_move_notify() in VFIO. * Added dma_buf_attach_revocable() check to VFIO DMABUF attach function. * Slightly changed commit messages. v2: https://patch.msgid.link/20260118-dmabuf-revoke-v2-0-a03bb27c0875@nvidia.com * Changed series to document the revoke semantics instead of implementing it. v1: https://patch.msgid.link/20260111-dmabuf-revoke-v1-0-fb4bcc8c259b@nvidia.com ------------------------------------------------------------------------- This series is based on latest VFIO fix, which will be sent to Linus very soon. https://lore.kernel.org/all/20260121-vfio-add-pin-v1-1-4e04916b17f1@nvidia.… Thanks ------------------------------------------------------------------------- This series documents a dma-buf “revoke” mechanism: to allow a dma-buf exporter to explicitly invalidate (“kill”) a shared buffer after it has been distributed to importers, so that further CPU and device access is prevented and importers reliably observe failure. The change in this series is to properly document and use existing core “revoked” state on the dma-buf object and a corresponding exporter-triggered revoke operation. dma-buf has quietly allowed calling move_notify on pinned dma-bufs, even though legacy importers using dma_buf_attach() would simply ignore these calls. The intention was that move_notify() would tell the importer to expedite it's unmapping process and once the importer is fully finished with DMA it would unmap the dma-buf which finally signals that the importer is no longer ever going to touch the memory again. Importers that touch past their unmap() call can trigger IOMMU errors, AER and beyond, however read-and-discard access between move_notify() and unmap is allowed. Thus, we can define the exporter's revoke sequence for pinned dma-buf as: dma_resv_lock(dmabuf->resv, NULL); // Prevent new mappings from being established priv->revoked = true; // Tell all importers to eventually unmap dma_buf_invalidate_mappings(dmabuf); // Wait for any inprogress fences on the old mapping dma_resv_wait_timeout(dmabuf->resv, DMA_RESV_USAGE_BOOKKEEP, false, MAX_SCHEDULE_TIMEOUT); dma_resv_unlock(dmabuf->resv, NULL); // Wait for all importers to complete unmap wait_for_completion(&priv->unmapp_comp); However, dma-buf also supports importers that don't do anything on move_notify(), and will not unmap the buffer in bounded time. Since such importers would cause the above sequence to hang, a new mechanism is needed to detect incompatible importers. Introduce dma_buf_attach_revocable() which if true indicates the above sequence is safe to use and will complete in kernel-only bounded time for this attachment. Unfortunately dma_buf_attach_revocable() is going to fail for the popular RDMA pinned importer, which means we cannot introduce it to existing places using pinned move_notify() without potentially breaking existing userspace flows. Existing exporters that only trigger this flow for RAS errors should not call dma_buf_attach_revocable() and will suffer an unbounded block on the final completion, hoping that the userspace will notice the RAS and clean things up. Without revoke support on the RDMA pinned importers it doesn't seem like any other non-breaking option is currently possible. For new exporters, like VFIO and RDMA, that have userspace triggered revoke events, the unbouned sleep would not be acceptable. They can call dma_buf_attach_revocable() and will not work with the RDMA pinned importer from day 0, preventing regressions. In the process add documentation explaining the above details. Thanks Signed-off-by: Leon Romanovsky <leonro(a)nvidia.com> --- Leon Romanovsky (8): dma-buf: Rename .move_notify() callback to a clearer identifier dma-buf: Rename dma_buf_move_notify() to dma_buf_invalidate_mappings() dma-buf: Always build with DMABUF_MOVE_NOTIFY vfio: Wait for dma-buf invalidation to complete dma-buf: Make .invalidate_mapping() truly optional dma-buf: Add dma_buf_attach_revocable() vfio: Permit VFIO to work with pinned importers iommufd: Add dma_buf_pin() drivers/dma-buf/Kconfig | 12 ----- drivers/dma-buf/dma-buf.c | 69 ++++++++++++++++++++----- drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 14 ++--- drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 2 +- drivers/gpu/drm/amd/amdkfd/Kconfig | 2 +- drivers/gpu/drm/virtio/virtgpu_prime.c | 2 +- drivers/gpu/drm/xe/tests/xe_dma_buf.c | 7 ++- drivers/gpu/drm/xe/xe_bo.c | 2 +- drivers/gpu/drm/xe/xe_dma_buf.c | 14 ++--- drivers/infiniband/core/umem_dmabuf.c | 13 ----- drivers/infiniband/hw/mlx5/mr.c | 2 +- drivers/iommu/iommufd/pages.c | 11 +++- drivers/iommu/iommufd/selftest.c | 2 +- drivers/vfio/pci/vfio_pci_dmabuf.c | 80 ++++++++++++++++++++++------- include/linux/dma-buf.h | 17 +++--- 15 files changed, 153 insertions(+), 96 deletions(-) --- base-commit: 61ceaf236115f20f4fdd7cf60f883ada1063349a change-id: 20251221-dmabuf-revoke-b90ef16e4236 Best regards, -- Leon Romanovsky <leonro(a)nvidia.com>

4 weeks, 1 day

Cryptera Chain Signals Summary – Focus On Transparency During Recovery Process

by Yulie Morgan

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1 month

Cryptera Chain Signals Experience – Realistic Forensics And Prevention Advice

by Yulie Morgan

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1 month

Detailed Feedback On Cryptera Chain Signals Support And Educational Value

by Yulie Morgan

My experience with Cryptera Chain Signals began after a wallet compromise earlier this year. From the initial call they set clear expectations and focused only on the evidence I could safely provide. The forensic work used multi-layer attribution to reconstruct the path, showing clusters and patterns I would never have spotted myself. They took time to explain concepts like address reuse risks and how graph analysis reveals hidden connections. The report included simplified diagrams that made the entire flow understandable. Although full recovery was not feasible due to rapid dispersal, the transparency helped me move forward. The sessions on prevention were equally useful. We discussed phishing variations, social engineering red flags, and everyday protections such as hardware keys and regular transaction reviews. I left with concrete steps I now follow, including dedicated crypto emails and bookmark verification. The entire engagement felt measured and educational rather than rushed. It provided both closure on the incident and tools for better security going forward. Cryptera Chain Signals Website: https://www.crypterachainsignals.com Email: info(a)crypterachainsignals.com

1 month

Cryptera Chain Signals Review – Insights Gained From Forensics Engagement

by Yulie Morgan

I engaged Cryptera Chain Signals after funds disappeared from a DeFi platform in early 2026. Their background of 28 years and steady client ratings gave me confidence in the structured approach. The first step was a secure upload of evidence, followed by a clear overview of the transaction path they planned to investigate. Using multi-layer attribution they mapped the movement across several chains, highlighting where the funds likely entered mixing services. The visuals made it easier to follow than raw blockchain data ever could. They explained why some endpoints become unreachable and what factors influence that outcome, including timing and platform compliance. No recovery was possible in my situation, but the analysis removed uncertainty. The educational side added real value. We covered rug-pull indicators such as liquidity locks, team transparency, and smart contract audits — topics I wish I had known earlier. Practical advice included offline seed storage, multi-signature setups, and basic due diligence checklists. Communication remained consistent and jargon-free throughout. For anyone wanting to understand both the technical side of what happened and how to avoid repeats, the process provided exactly that. Cryptera Chain Signals Website: https://www.crypterachainsignals.com Email: info(a)crypterachainsignals.com

1 month

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