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SubjectRe: [PATCH v5 0/9] Enable Sub-page Write Protection Support
On Tue, Sep 17, 2019 at 04:52:55PM +0800, Yang, Weijiang wrote:
Hi, Paolo,
Could you review this v5 patch at your convenience?
Thanks a lot!

> 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

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