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Message-ID: <c10bf9c2-e073-479d-ad1c-6796c592d333@amd.com> Date: Fri, 9 May 2025 13:04:58 +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 Ping? Also, since there is pushback on 01/12 "dma-buf: Introduce dma_buf_get_pfn_unlocked() kAPI", what is the plan now? Thanks, On 29/4/25 17:50, Alexey Kardashevskiy wrote: > > > On 29/4/25 16:48, Alexey Kardashevskiy wrote: >> 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, > > > More to the point, to make it work, QEMU needs to register VFIO MMIO BAR with KVM_SET_USER_MEMORY_REGION2 which passes slot->guest_memfd to KVM which essentially comes from VFIORegion->mmaps[0].mem->ram_block->guest_memfd. But since you disabled mmap for private MMIO, there is no MR which QEMU would even try registering as KVM memslot and there are many ways to fix it. I took a shortcut and reenabled mmap() but wonder what exactly you did. Makes sense? 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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