Re: [PATCH v5 0/9] Enable Sub-page Write Protection Support

[Yang Weijiang]

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