Hi, This is version 2 of the "KVM Address Space Isolation" RFC. The code has been completely changed compared to v1 and it now provides a generic kernel framework which provides Address Space Isolation; and KVM is now a simple consumer of that framework. That's why the RFC title has been changed from "KVM Address Space Isolation" to "Kernel Address Space Isolation". Kernel Address Space Isolation aims to use address spaces to isolate some parts of the kernel (for example KVM) to prevent leaking sensitive data between hyper-threads under speculative execution attacks. You can refer to the first version of this RFC for more context: https://lkml.org/lkml/2019/5/13/515 The new code is still a proof of concept. It is much more stable than v1: I am able to run a VM with a full OS (and also a nested VM) with multiple vcpus. But it looks like there are still some corner cases which cause the system to crash/hang. I am looking for feedback about this new approach where address space isolation is provided by the kernel, and KVM is a just a consumer of this new framework. Changes ======= - Address Space Isolation (ASI) is now provided as a kernel framework: interfaces for creating and managing an ASI are provided by the kernel, there are not implemented in KVM. - An ASI is associated with a page-table, we don't use mm anymore. Entering isolation is done by just updating CR3 to use the ASI page-table. Exiting isolation restores CR3 with the CR3 value present before entering isolation. - Isolation is exited at the beginning of any interrupt/exception handler, and on context switch. - Isolation doesn't disable interrupt, but if an interrupt occurs the interrupt handler will exit isolation. - The current stack is mapped when entering isolation and unmapped when exiting isolation. - The current task is not mapped by default, but there's an option to map it. In such a case, the current task is mapped when entering isolation and unmap when exiting isolation. - Kernel code mapped to the ASI page-table has been reduced to: . the entire kernel (I still need to test with only the kernel text) . the cpu entry area (because we need the GDT to be mapped) . the cpu ASI session (for managing ASI) . the current stack - Optionally, an ASI can request the following kernel mapping to be added: . the stack canary . the cpu offsets (this_cpu_off) . the current task . RCU data (rcu_data) . CPU HW events (cpu_hw_events). All these optional mappings are used for KVM isolation. Patches: ======== The proposed patches provides a framework for creating an Address Space Isolation (ASI) (represented by a struct asi). The ASI has a page-table which can be populated by copying mappings from the kernel page-table. The ASI can then be entered/exited by switching between the kernel page-table and the ASI page-table. In addition, any interrupt, exception or context switch will automatically abort and exit the isolation. Finally patches use the ASI framework to implement KVM isolation. - 01-03: Core of the ASI framework: create/destroy ASI, enter/exit/abort isolation, ASI page-fault handler. - 04-14: Functions to manage, populate and clear an ASI page-table. - 15-20: ASI core mappings and optional mappings. - 21: Make functions to read cr3/cr4 ASI aware - 22-26: Use ASI in KVM to provide isolation for VMExit handlers. API Overview: ============= Here is a short description of the main ASI functions provided by the framwork. struct asi *asi_create(int map_flags) Create an Address Space Isolation (ASI). map_flags can be used to specify optional kernel mapping to be added to the ASI page-table (for example, ASI_MAP_STACK_CANARY to map the stack canary). void asi_destroy(struct asi *asi) Destroy an ASI. int asi_enter(struct asi *asi) Enter isolation for the specified ASI. This switches from the kernel page-table to the page-table associated with the ASI. void asi_exit(struct asi *asi) Exit isolation for the specified ASI. This switches back to the kernel page-table int asi_map(struct asi *asi, void *ptr, unsigned long size); Copy kernel mapping to the specified ASI page-table. void asi_unmap(struct asi *asi, void *ptr); Clear kernel mapping from the specified ASI page-table. ---- Alexandre Chartre (23): mm/x86: Introduce kernel address space isolation mm/asi: Abort isolation on interrupt, exception and context switch mm/asi: Handle page fault due to address space isolation mm/asi: Functions to track buffers allocated for an ASI page-table mm/asi: Add ASI page-table entry offset functions mm/asi: Add ASI page-table entry allocation functions mm/asi: Add ASI page-table entry set functions mm/asi: Functions to populate an ASI page-table from a VA range mm/asi: Helper functions to map module into ASI mm/asi: Keep track of VA ranges mapped in ASI page-table mm/asi: Functions to clear ASI page-table entries for a VA range mm/asi: Function to copy page-table entries for percpu buffer mm/asi: Add asi_remap() function mm/asi: Handle ASI mapped range leaks and overlaps mm/asi: Initialize the ASI page-table with core mappings mm/asi: Option to map current task into ASI rcu: Move tree.h static forward declarations to tree.c rcu: Make percpu rcu_data non-static mm/asi: Add option to map RCU data mm/asi: Add option to map cpu_hw_events mm/asi: Make functions to read cr3/cr4 ASI aware KVM: x86/asi: Populate the KVM ASI page-table KVM: x86/asi: Map KVM memslots and IO buses into KVM ASI Liran Alon (3): KVM: x86/asi: Introduce address_space_isolation module parameter KVM: x86/asi: Introduce KVM address space isolation KVM: x86/asi: Switch to KVM address space on entry to guest arch/x86/entry/entry_64.S | 42 ++- arch/x86/include/asm/asi.h | 237 ++++++++ arch/x86/include/asm/mmu_context.h | 20 +- arch/x86/include/asm/tlbflush.h | 10 + arch/x86/kernel/asm-offsets.c | 4 + arch/x86/kvm/Makefile | 3 +- arch/x86/kvm/mmu.c | 2 +- arch/x86/kvm/vmx/isolation.c | 231 ++++++++ arch/x86/kvm/vmx/vmx.c | 14 +- arch/x86/kvm/vmx/vmx.h | 24 + arch/x86/kvm/x86.c | 68 +++- arch/x86/kvm/x86.h | 1 + arch/x86/mm/Makefile | 2 + arch/x86/mm/asi.c | 459 +++++++++++++++ arch/x86/mm/asi_pagetable.c | 1077 ++++++++++++++++++++++++++++++++++++ arch/x86/mm/fault.c | 7 + include/linux/kvm_host.h | 7 + kernel/rcu/tree.c | 56 ++- kernel/rcu/tree.h | 56 +-- kernel/sched/core.c | 4 + security/Kconfig | 10 + 21 files changed, 2269 insertions(+), 65 deletions(-) create mode 100644 arch/x86/include/asm/asi.h create mode 100644 arch/x86/kvm/vmx/isolation.c create mode 100644 arch/x86/mm/asi.c create mode 100644 arch/x86/mm/asi_pagetable.c
