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Message-ID: <4b6dc759-86fd-47a7-a206-66b25a0ccc6d@amd.com> Date: Tue, 29 Apr 2025 17:50:01 +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 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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