EPT-Based Sub-Page write Protection(SPP)is a HW capability which allows Virtual Machine Monitor(VMM) to specify write-permission for guest physical memory at a sub-page(128 byte) granularity. When this capability is enabled, the CPU enforces write-access check for sub-pages within a 4KB page. The feature is targeted to provide fine-grained memory protection for usages such as device virtualization, memory check-point and VM introspection etc. SPP is active when the "sub-page write protection" (bit 23) is 1 in Secondary VM-Execution Controls. The feature is backed with a Sub-Page Permission Table(SPPT), SPPT is referenced via a 64-bit control field called Sub-Page Permission Table Pointer (SPPTP) which contains a 4K-aligned physical address. To enable SPP for certain physical page, the gfn should be first mapped to a 4KB entry, then set bit 61 of the corresponding EPT leaf entry. While HW walks EPT, if bit 61 is set, it traverses SPPT with the guset physical address to find out the sub-page permissions at the leaf entry. If the corresponding bit is set, write to sub-page is permitted, otherwise, SPP induced EPT violation is generated. This patch serial passed SPP function test and selftest on Ice-Lake platform. Please refer to the SPP introduction document in this patch set and Intel SDM for details: Intel SDM: https://software.intel.com/sites/default/files/managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf SPP selftest patch: https://lkml.org/lkml/2019/6/18/1197 Previous patch: https://lkml.org/lkml/2019/8/14/97 Patch 1: Introduction to SPP. Patch 2: Add SPP related flags and control bits. Patch 3: Functions for SPPT setup. Patch 4: Add SPP access bitmaps for memslots. Patch 5: Introduce SPP {init,set,get} functions Patch 6: Implement User space access IOCTLs. Patch 7: Set up SPP paging table at vm-entry/exit. Patch 8: Enable lazy mode SPPT setup. Patch 9: Handle SPP protected pages when VM memory changes Change logs: V5 -> V4: 1. Enable SPP support for Hugepage(1GB/2MB) to extend application. 2. Make SPP miss vm-exit handler as the unified place to set up SPPT. 3. If SPP protected pages are access-tracked or dirty-page-tracked, store SPP flag in reserved address bit, restore it in fast_page_fault() handler. 4. Move SPP specific functions to vmx/spp.c and vmx/spp.h 5. Rebased code to kernel v5.3 6. Other change suggested by KVM community. V3 -> V4: 1. Modified documentation to make it consistent with patches. 2. Allocated SPPT root page in init_spp() instead of vmx_set_cr3() to avoid SPPT miss error. 3. Added back co-developers and sign-offs. V2 -> V3: 1. Rebased patches to kernel 5.1 release 2. Deferred SPPT setup to EPT fault handler if the page is not available while set_subpage() is being called. 3. Added init IOCTL to reduce extra cost if SPP is not used. 4. Refactored patch structure, cleaned up cross referenced functions. 5. Added code to deal with memory swapping/migration/shrinker cases. V2 -> V1: 1. Rebased to 4.20-rc1 2. Move VMCS change to a separated patch. 3. Code refine and Bug fix Yang Weijiang (9): Documentation: Introduce EPT based Subpage Protection vmx: spp: Add control flags for Sub-Page Protection(SPP) mmu: spp: Add SPP Table setup functions mmu: spp: Add functions to create/destroy SPP bitmap block mmu: spp: Introduce SPP {init,set,get} functions x86: spp: Introduce user-space SPP IOCTLs vmx: spp: Set up SPP paging table at vm-entry/exit mmu: spp: Enable Lazy mode SPP protection mmu: spp: Handle SPP protected pages when VM memory changes Documentation/virtual/kvm/spp_kvm.txt | 178 +++++++ arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/kvm_host.h | 10 +- arch/x86/include/asm/vmx.h | 10 + arch/x86/include/uapi/asm/vmx.h | 2 + arch/x86/kernel/cpu/intel.c | 4 + arch/x86/kvm/mmu.c | 78 ++- arch/x86/kvm/mmu.h | 2 + arch/x86/kvm/vmx/capabilities.h | 5 + arch/x86/kvm/vmx/spp.c | 651 ++++++++++++++++++++++++++ arch/x86/kvm/vmx/spp.h | 27 ++ arch/x86/kvm/vmx/vmx.c | 99 ++++ arch/x86/kvm/x86.c | 51 ++ include/uapi/linux/kvm.h | 17 + 14 files changed, 1133 insertions(+), 2 deletions(-) create mode 100644 Documentation/virtual/kvm/spp_kvm.txt create mode 100644 arch/x86/kvm/vmx/spp.c create mode 100644 arch/x86/kvm/vmx/spp.h -- 2.17.2
