Message-ID: <371ab632-d167-4720-8f0d-57be1e3fee84@amd.com>
Date: Tue, 29 Apr 2025 16:48:27 +1000
From: Alexey Kardashevskiy <aik@....com>
To: Xu Yilun <yilun.xu@...ux.intel.com>, kvm@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
 linaro-mm-sig@...ts.linaro.org, sumit.semwal@...aro.org,
 christian.koenig@....com, pbonzini@...hat.com, seanjc@...gle.com,
 alex.williamson@...hat.com, jgg@...dia.com, vivek.kasireddy@...el.com,
 dan.j.williams@...el.com
Cc: yilun.xu@...el.com, linux-coco@...ts.linux.dev,
 linux-kernel@...r.kernel.org, lukas@...ner.de, yan.y.zhao@...el.com,
 daniel.vetter@...ll.ch, leon@...nel.org, baolu.lu@...ux.intel.com,
 zhenzhong.duan@...el.com, tao1.su@...el.com
Subject: Re: [RFC PATCH 00/12] Private MMIO support for private assigned dev

On 8/1/25 01:27, Xu Yilun wrote:
> This series is based on an earlier kvm-coco-queue version (v6.12-rc2)

Has this been pushed somewhere public? The patchset does not apply on top of v6.12-rc2, for example (I fixed locally).
Also, is there somewhere a QEMU tree using this? I am trying to use this new DMA_BUF feature and this require quite some not so obvious plumbing. Thanks,


> which includes all basic TDX patches.
> 
> The series is to start the early stage discussion of the private MMIO
> handling for Coco-VM, which is part of the Private Device
> Assignment (aka TEE-IO, TIO) enabling. There are already some
> disscusion about the context of TIO:
> 
> https://lore.kernel.org/linux-coco/173343739517.1074769.13134786548545925484.stgit@dwillia2-xfh.jf.intel.com/
> https://lore.kernel.org/all/20240823132137.336874-1-aik@amd.com/
> 
> Private MMIOs are resources owned by Private assigned devices. Like
> private memory, they are also not intended to be accessed by host, only
> accessible by Coco-VM via some secondary MMUs (e.g. Secure EPT). This
> series is for KVM to map these MMIO resources without firstly mapping
> into the host. For this purpose, This series uses the FD based MMIO
> resources for secure mapping, and the dma-buf is chosen as the FD based
> backend, just like guest_memfd for private memory. Patch 6 in this
> series has more detailed description.
> 
> 
> Patch 1 changes dma-buf core, expose a new kAPI for importers to get
> dma-buf's PFN without DMA mapping. KVM could use this kAPI to build
> GPA -> HPA mapping in KVM MMU.
> 
> Patch 2-4 are from Jason & Vivek, allow vfio-pci to export MMIO
> resources as dma-buf. The original series are for native P2P DMA and
> focus on p2p DMA mapping opens. I removed these p2p DMA mapping code
> just to focus the early stage discussion of private MMIO. The original
> series:
> 
> https://lore.kernel.org/all/0-v2-472615b3877e+28f7-vfio_dma_buf_jgg@nvidia.com/
> https://lore.kernel.org/kvm/20240624065552.1572580-1-vivek.kasireddy@intel.com/
> 
> Patch 5 is the implementation of get_pfn() callback for vfio dma-buf
> exporter.
> 
> Patch 6-7 is about KVM supports the private MMIO memory slot backed by
> vfio dma-buf.
> 
> Patch 8-10 is about how KVM verifies the user provided dma-buf fd
> eligible for private MMIO slot.
> 
> Patch 11-12 is the example of how KVM TDX setup the Secure EPT for
> private MMIO.
> 
> 
> TODOs:
> 
> - Follow up the evolving of original VFIO dma-buf series.
> - Follow up the evolving of basic TDX patches.
> 
> 
> Vivek Kasireddy (3):
>    vfio: Export vfio device get and put registration helpers
>    vfio/pci: Share the core device pointer while invoking feature
>      functions
>    vfio/pci: Allow MMIO regions to be exported through dma-buf
> 
> Xu Yilun (9):
>    dma-buf: Introduce dma_buf_get_pfn_unlocked() kAPI
>    vfio/pci: Support get_pfn() callback for dma-buf
>    KVM: Support vfio_dmabuf backed MMIO region
>    KVM: x86/mmu: Handle page fault for vfio_dmabuf backed MMIO
>    vfio/pci: Create host unaccessible dma-buf for private device
>    vfio/pci: Export vfio dma-buf specific info for importers
>    KVM: vfio_dmabuf: Fetch VFIO specific dma-buf data for sanity check
>    KVM: x86/mmu: Export kvm_is_mmio_pfn()
>    KVM: TDX: Implement TDX specific private MMIO map/unmap for SEPT
> 
>   Documentation/virt/kvm/api.rst     |   7 +
>   arch/x86/include/asm/tdx.h         |   3 +
>   arch/x86/kvm/mmu.h                 |   1 +
>   arch/x86/kvm/mmu/mmu.c             |  25 ++-
>   arch/x86/kvm/mmu/spte.c            |   3 +-
>   arch/x86/kvm/vmx/tdx.c             |  57 +++++-
>   arch/x86/virt/vmx/tdx/tdx.c        |  52 ++++++
>   arch/x86/virt/vmx/tdx/tdx.h        |   3 +
>   drivers/dma-buf/dma-buf.c          |  90 ++++++++--
>   drivers/vfio/device_cdev.c         |   9 +-
>   drivers/vfio/pci/Makefile          |   1 +
>   drivers/vfio/pci/dma_buf.c         | 273 +++++++++++++++++++++++++++++
>   drivers/vfio/pci/vfio_pci_config.c |  22 ++-
>   drivers/vfio/pci/vfio_pci_core.c   |  64 +++++--
>   drivers/vfio/pci/vfio_pci_priv.h   |  27 +++
>   drivers/vfio/pci/vfio_pci_rdwr.c   |   3 +
>   drivers/vfio/vfio_main.c           |   2 +
>   include/linux/dma-buf.h            |  13 ++
>   include/linux/kvm_host.h           |  25 ++-
>   include/linux/vfio.h               |  22 +++
>   include/linux/vfio_pci_core.h      |   1 +
>   include/uapi/linux/kvm.h           |   1 +
>   include/uapi/linux/vfio.h          |  34 +++-
>   virt/kvm/Kconfig                   |   6 +
>   virt/kvm/Makefile.kvm              |   1 +
>   virt/kvm/kvm_main.c                |  32 +++-
>   virt/kvm/kvm_mm.h                  |  19 ++
>   virt/kvm/vfio_dmabuf.c             | 151 ++++++++++++++++
>   28 files changed, 896 insertions(+), 51 deletions(-)
>   create mode 100644 drivers/vfio/pci/dma_buf.c
>   create mode 100644 virt/kvm/vfio_dmabuf.c
> 

-- 
Alexey

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