On Thu, Apr 20, 2023 at 3:47 AM Atish Patra <atishp@xxxxxxxxxxxx> wrote: > > This patch series adds the RISC-V Confidential VM Extension (CoVE) support to > Linux kernel. The RISC-V CoVE specification introduces non-ISA, SBI APIs. These > APIs enable a confidential environment in which a guest VM's data can be isolated > from the host while the host retains control of guest VM management and platform > resources(memory, CPU, I/O). > > This is a very early WIP work. We want to share this with the community to get any > feedback on overall architecture and direction. Any other feedback is welcome too. > > The detailed CoVE architecture document can be found here [0]. It used to be > called AP-TEE and renamed to CoVE recently to avoid overloading term of TEE in > general. The specification is in the draft stages and is subjected to change based > on the feedback from the community. > > The CoVE specification introduces 3 new SBI extensions. > COVH - CoVE Host side interface > COVG - CoVE Guest side interface > COVI - CoVE Secure Interrupt management extension > > Some key acronyms introduced: > > TSM - TEE Security Manager > TVM - TEE VM (aka Confidential VM) > > CoVE Architecture: > ==================== > The CoVE APIs are designed to be implementation and architecture agnostic, > allowing for different deployment models while retaining common host and guest > kernel code. Two examples are shown in Figure 1 and Figure 2. > As shown in both figures, the architecture introduces a new software component > called the "TEE Security Manager" (TSM) that runs in HS mode. The TSM has minimal > hw attested footprint on TCB as it is a passive component that doesn't support > scheduling or timer interrupts. Both example deployment models provide memory > isolation between the host and the TEE VM (TVM). > > > Non secure world | Secure world | > | | > Non | | > Virtualized | Virtualized | Virtualized Virtualized | > Env | Env | Env Env | > +----------+ | +----------+ | +----------+ +----------+ | -------------- > | | | | | | | | | | | > | Host Apps| | | Apps | | | Apps | | Apps | | VU-Mode > | (VMM) | | | | | | | | | | > +----------+ | +----------+ | +----------+ +----------+ | -------------- > | | +----------+ | +----------+ +----------+ | > | | | | | | | | | | > | | | | | | TVM | | TVM | | > | | | Guest | | | Guest | | Guest | | VS-Mode > Syscalls | +----------+ | +----------+ +----------+ | > | | | | | > | SBI | SBI(COVG + COVI) | > | | | | | > +--------------------------+ | +---------------------------+ -------------- > | Host (Linux) | | | TSM (Salus) | > +--------------------------+ | +---------------------------+ > | | | HS-Mode > SBI (COVH + COVI) | SBI (COVH + COVI) > | | | > +-----------------------------------------------------------+ -------------- > | Firmware(OpenSBI) + TSM Driver | M-Mode > +-----------------------------------------------------------+ -------------- > +----------------------------------------------------------------------------- > | Hardware (RISC-V CPU + RoT + IOMMU) > +---------------------------------------------------------------------------- > Figure 1: Host in HS model > > > The deployment model shown in Figure 1 runs the host in HS mode where it is peer > to the TSM which also runs in HS mode. It requires another component known as TSM > Driver running in higher privilege mode than host/TSM. It is responsible for switching > the context between the host and the TSM. TSM driver also manages the platform > specific hardware solution via confidential domain bit as described in the specification[0] > to provide the required memory isolation. > > > Non secure world | Secure world > | > Virtualized Env | Virtualized Virtualized | > Env Env | > +-------------------------+ | +----------+ +----------+ | ------------ > | | | | | | | | | | | > | Host Apps| | | Apps | | | Apps | | Apps | | VU-Mode > +----------+ | +----------+ | +----------+ +----------+ | ------------ > | | | | | > Syscalls SBI | | | | > | | | | | > +--------------------------+ | +-----------+ +-----------+ | > | Host (Linux) | | | TVM Guest| | TVM Guest| | VS-Mode > +--------------------------+ | +-----------+ +-----------+ | > | | | | | > SBI (COVH + COVI) | SBI SBI | > | | (COVG + COVI) (COVG + COVI)| > | | | | | > +-----------------------------------------------------------+ -------------- > | TSM(Salus) | HS-Mode > +-----------------------------------------------------------+ -------------- > | > SBI > | > +---------------------------------------------------------+ -------------- > | Firmware(OpenSBI) | M-Mode > +---------------------------------------------------------+ -------------- > +----------------------------------------------------------------------------- > | Hardware (RISC-V CPU + RoT + IOMMU) > +---------------------------------------------------------------------------- > Figure 2: Host in VS model > > > The deployment model shown in Figure 2 simplifies the context switch and memory isolation > by running the host in VS mode as a guest of TSM. Thus, the memory isolation is > achieved by gstage mapping by the TSM. We don't need any additional hardware confidential > domain bit to provide memory isolation. The downside of this model the host has to run the > non-confidential VMs in nested environment which may have lower performance (yet to be measured). > The current implementation Salus(TSM) doesn't support full nested virtualization yet. > > The platform must have a RoT to provide attestation in either model. > This patch series implements the APIs defined by CoVE. The current TSM implementation > allows the host to run TVMs as shown in figure 2. We are working on deployment > model 1 in parallel. We do not expect any significant changes in either host/guest side > ABI due to that. > > Shared memory between the host & TSM: > ===================================== > To accelerate the H-mode CSR/GPR access, CoVE also reuses the Nested Acceleration (NACL) > SBI extension[1]. NACL defines a per physical cpu shared memory area that is allocated > at the boot. It allows the host running in VS mode to access H-mode CSR/GPR easily > without trapping into the TSM. The CoVE specification clearly defines the exact > state of the shared memory with r/w permissions at every call. > > Secure Interrupt management: > =========================== > The CoVE specification relies on the MSI based interrupt scheme defined in Advanced Interrupt > Architecture specification[2]. The COVI SBI extension adds functions to bind > a guest interrupt file to a TVMs. After that, only TCB components (TSM, TVM, TSM driver) > can modify that. The host can inject an interrupt via TSM only. > The TVMs are also in complete control of which interrupts it can receive. By default, > all interrupts are denied. In this proof-of-concept implementation, all the interrupts > are allowed by the guest at boot time to keep it simple. > > Device I/O: > =========== > In order to support paravirt I/O devices, SWIOTLB bounce buffer must be used by the > guest. As the host can not access confidential memory, this buffer memory > must be shared with the host via share/unshare functions defined in COVG SBI extension. > RISC-V implementation achieves this generalizing mem_encrypt_init() similar to TDX/SEV/CCA. > That's why, the CoVE Guest is only allowed to use virtio devices with VIRTIO_F_ACCESS_PLATFORM > and VIRTIO_F_VERSION_1 as they force virtio drivers to use the DMA API. > > MMIO emulation: > ====================== > TVM can register regions of address space as MMIO regions to be emulated by > the host. TSM provides explicit SBI functions i.e. SBI_EXT_COVG_[ADD/REMOVE]_MMIO_REGION > to request/remove MMIO regions. Any reads or writes to those MMIO region after > SBI_EXT_COVG_ADD_MMIO_REGION call are forwarded to the host for emulation. > > This series allows any ioremapped memory to be emulated as MMIO region with > above APIs via arch hookups inspired from pKVM work. We are aware that this model > doesn't address all the threat vectors. We have also implemented the device > filtering/authorization approach adopted by TDX[4]. However, those patches are not > part of this series as the base TDX patches are still under active development. > RISC-V CoVE will also adapt the revamped device filtering work once it is accepted > by the Linux community in the future. > > The direct assignment of devices are a work in progress and will be added in the future[4]. > > VMM support: > ============ > This series is only tested with kvmtool support. Other VMM support (qemu-kvm, crossvm/rust-vmm) > will be added later. > > Test cases: > =========== > We are working on kvm selftest for CoVE. We will post them as soon as they are ready. > We haven't started any work on kvm unit-tests as RISC-V doesn't have basic infrastructure > to support that. Once the kvm uni-test infrastructure is in place, we will add > support for CoVE as well. > > Open design questions: > ====================== > > 1. The current implementation has two separate configs for guest(CONFIG_RISCV_COVE_GUEST) > and the host (RISCV_COVE_HOST). The default defconfig will enable both so that > same unified image works as both host & guest. Most likely distro prefer this way > to minimize the maintenance burden but some may want a minimal CoVE guest image > that has only hardened drivers. In addition to that, Android runs a microdroid instance > in the confidential guests. A separate config will help in those case. Please let us > know if there is any concern with two configs. > > 2. Lazy gstage page allocation vs upfront allocation with page pool. > Currently, all gstage mappings happen at runtime during the fault. This is expensive > as we need to convert that page to confidential memory as well. A page pool framework > may be a better choice which can hold all the confidential pages which can be > pre-allocated upfront. A generic page pool infrastructure may benefit other CC solutions ? > > 3. In order to allow both confidential VM and non-confidential VM, the series > uses regular branching instead of static branches for CoVE VM specific cases through > out KVM. That may cause a few more branch penalties while running regular VMs. > The alternate option is to use function pointers for any function that needs to > take a different path. As per my understanding, that would be worse than branches. > > Patch organization: > =================== > This series depends on quite a few RISC-V patches that are not upstream yet. > Here are the dependencies. > > 1. RISC-V IPI improvement series > 2. RISC-V AIA support series. > 3. RISC-V NACL support series > > In this series, PATCH [0-5] are generic improvement and cleanup patches which > can be merged independently. > > PATCH [6-26, 34-37] adds host side for CoVE. > PATCH [27-33] adds the interrupt related changes. > PATCH [34-49] Adds the guest side changes for CoVE. > > The TSM project is written in rust and can be found here: > https://github.com/rivosinc/salus > > Running the stack > ==================== > > To run/test the stack, you would need the following components : > > 1) Qemu > 2) Common Host & Guest Kernel > 3) kvmtool > 4) Host RootFS with KVMTOOL and Guest Kernel > 5) Salus > > The detailed steps are available at[6] > > The Linux kernel patches are also available at [7] and the kvmtool patches > are available at [8]. > > TODOs > ======= > As this is a very early work, the todo list is quite long :). > Here are some of them (not in any specific order) > > 1. Support fd based private memory interface proposed in > https://lkml.org/lkml/2022/1/18/395 > 2. Align with updated guest runtime device filtering approach. > 3. IOMMU integration > 4. Dedicated device assignment via TDSIP & SPDM[4] > 5. Support huge pages > 6. Page pool allocator to avoid convert/reclaim at every fault > 7. Other VMM support (qemu-kvm, crossvm) > 8. Complete the PoC for the deployment model 1 where host runs in HS mode > 9. Attestation integration > 10. Harden the interrupt allowed list > 11. kvm self-tests support for CoVE > 11. kvm unit-tests support for CoVE > 12. Guest hardening > 13. Port pKVM on RISC-V using CoVE > 14. Any other ? > > Links > ============ > [0] CoVE architecture Specification. > https://github.com/riscv-non-isa/riscv-ap-tee/blob/main/specification/riscv-aptee-spec.pdf I just noticed that this link is broken due to a recent PR merge. Here is the updated link https://github.com/riscv-non-isa/riscv-ap-tee/blob/main/specification/riscv-cove.pdf Sorry for the noise. > [1] https://lists.riscv.org/g/sig-hypervisors/message/260 > [2] https://github.com/riscv/riscv-aia/releases/download/1.0-RC2/riscv-interrupts-1.0-RC2.pdf > [3] https://github.com/rivosinc/linux/tree/cove_integration_device_filtering1 > [4] https://github.com/intel/tdx/commits/guest-filter-upstream > [5] https://lists.riscv.org/g/tech-ap-tee/message/83 > [6] https://github.com/rivosinc/cove/wiki/CoVE-KVM-RISCV64-on-QEMU > [7] https://github.com/rivosinc/linux/commits/cove-integration > [8] https://github.com/rivosinc/kvmtool/tree/cove-integration-03072023 > > Atish Patra (33): > RISC-V: KVM: Improve KVM error reporting to the user space > RISC-V: KVM: Invoke aia_update with preempt disabled/irq enabled > RISC-V: KVM: Add a helper function to get pgd size > RISC-V: Add COVH SBI extensions definitions > RISC-V: KVM: Implement COVH SBI extension > RISC-V: KVM: Add a barebone CoVE implementation > RISC-V: KVM: Add UABI to support static memory region attestation > RISC-V: KVM: Add CoVE related nacl helpers > RISC-V: KVM: Implement static memory region measurement > RISC-V: KVM: Use the new VM IOCTL for measuring pages > RISC-V: KVM: Exit to the user space for trap redirection > RISC-V: KVM: Return early for gstage modifications > RISC-V: KVM: Skip dirty logging updates for TVM > RISC-V: KVM: Add a helper function to trigger fence ops > RISC-V: KVM: Skip most VCPU requests for TVMs > RISC-V : KVM: Skip vmid/hgatp management for TVMs > RISC-V: KVM: Skip TLB management for TVMs > RISC-V: KVM: Register memory regions as confidential for TVMs > RISC-V: KVM: Add gstage mapping for TVMs > RISC-V: KVM: Handle SBI call forward from the TSM > RISC-V: KVM: Implement vcpu load/put functions for CoVE guests > RISC-V: KVM: Wireup TVM world switch > RISC-V: KVM: Skip HVIP update for TVMs > RISC-V: KVM: Implement COVI SBI extension > RISC-V: KVM: Add interrupt management functions for TVM > RISC-V: KVM: Skip AIA CSR updates for TVMs > RISC-V: KVM: Perform limited operations in hardware enable/disable > RISC-V: KVM: Indicate no support user space emulated IRQCHIP > RISC-V: KVM: Add AIA support for TVMs > RISC-V: KVM: Hookup TVM VCPU init/destroy > RISC-V: KVM: Initialize CoVE > RISC-V: KVM: Add TVM init/destroy calls > drivers/hvc: sbi: Disable HVC console for TVMs > > Rajnesh Kanwal (15): > mm/vmalloc: Introduce arch hooks to notify ioremap/unmap changes > RISC-V: KVM: Update timer functionality for TVMs. > RISC-V: Add COVI extension definitions > RISC-V: KVM: Read/write gprs from/to shmem in case of TVM VCPU. > RISC-V: Add COVG SBI extension definitions > RISC-V: Add CoVE guest config and helper functions > RISC-V: Implement COVG SBI extension > RISC-V: COVE: Add COVH invalidate, validate, promote, demote and > remove APIs. > RISC-V: KVM: Add host side support to handle COVG SBI calls. > RISC-V: Allow host to inject any ext interrupt id to a CoVE guest. > RISC-V: Add base memory encryption functions. > RISC-V: Add cc_platform_has() for RISC-V for CoVE > RISC-V: ioremap: Implement for arch specific ioremap hooks > riscv/virtio: Have CoVE guests enforce restricted virtio memory > access. > RISC-V: Add shared bounce buffer to support DBCN for CoVE Guest. > > arch/riscv/Kbuild | 2 + > arch/riscv/Kconfig | 27 + > arch/riscv/cove/Makefile | 2 + > arch/riscv/cove/core.c | 40 + > arch/riscv/cove/cove_guest_sbi.c | 109 +++ > arch/riscv/include/asm/cove.h | 27 + > arch/riscv/include/asm/covg_sbi.h | 38 + > arch/riscv/include/asm/csr.h | 2 + > arch/riscv/include/asm/kvm_cove.h | 206 +++++ > arch/riscv/include/asm/kvm_cove_sbi.h | 101 +++ > arch/riscv/include/asm/kvm_host.h | 10 +- > arch/riscv/include/asm/kvm_vcpu_sbi.h | 3 + > arch/riscv/include/asm/mem_encrypt.h | 26 + > arch/riscv/include/asm/sbi.h | 107 +++ > arch/riscv/include/uapi/asm/kvm.h | 17 + > arch/riscv/kernel/irq.c | 12 + > arch/riscv/kernel/setup.c | 2 + > arch/riscv/kvm/Makefile | 1 + > arch/riscv/kvm/aia.c | 101 ++- > arch/riscv/kvm/aia_device.c | 41 +- > arch/riscv/kvm/aia_imsic.c | 127 ++- > arch/riscv/kvm/cove.c | 1005 +++++++++++++++++++++++ > arch/riscv/kvm/cove_sbi.c | 490 +++++++++++ > arch/riscv/kvm/main.c | 30 +- > arch/riscv/kvm/mmu.c | 45 +- > arch/riscv/kvm/tlb.c | 11 +- > arch/riscv/kvm/vcpu.c | 69 +- > arch/riscv/kvm/vcpu_exit.c | 34 +- > arch/riscv/kvm/vcpu_insn.c | 115 ++- > arch/riscv/kvm/vcpu_sbi.c | 16 + > arch/riscv/kvm/vcpu_sbi_covg.c | 232 ++++++ > arch/riscv/kvm/vcpu_timer.c | 26 +- > arch/riscv/kvm/vm.c | 34 +- > arch/riscv/kvm/vmid.c | 17 +- > arch/riscv/mm/Makefile | 3 + > arch/riscv/mm/init.c | 17 +- > arch/riscv/mm/ioremap.c | 45 + > arch/riscv/mm/mem_encrypt.c | 61 ++ > drivers/tty/hvc/hvc_riscv_sbi.c | 5 + > drivers/tty/serial/earlycon-riscv-sbi.c | 51 +- > include/uapi/linux/kvm.h | 8 + > mm/vmalloc.c | 16 + > 42 files changed, 3222 insertions(+), 109 deletions(-) > create mode 100644 arch/riscv/cove/Makefile > create mode 100644 arch/riscv/cove/core.c > create mode 100644 arch/riscv/cove/cove_guest_sbi.c > create mode 100644 arch/riscv/include/asm/cove.h > create mode 100644 arch/riscv/include/asm/covg_sbi.h > create mode 100644 arch/riscv/include/asm/kvm_cove.h > create mode 100644 arch/riscv/include/asm/kvm_cove_sbi.h > create mode 100644 arch/riscv/include/asm/mem_encrypt.h > create mode 100644 arch/riscv/kvm/cove.c > create mode 100644 arch/riscv/kvm/cove_sbi.c > create mode 100644 arch/riscv/kvm/vcpu_sbi_covg.c > create mode 100644 arch/riscv/mm/ioremap.c > create mode 100644 arch/riscv/mm/mem_encrypt.c > > -- > 2.25.1 > -- Regards, Atish
