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Date: Tue, 12 Nov 2019 16:33:52 +0800
From: Yang Weijiang <weijiang.yang@...el.com>
To: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
pbonzini@...hat.com, jmattson@...gle.com,
sean.j.christopherson@...el.com
Cc: yu.c.zhang@...ux.intel.com, alazar@...defender.com,
edwin.zhai@...el.com, Yang Weijiang <weijiang.yang@...el.com>
Subject: Re: [PATCH v6 0/9] Enable Sub-Page Write Protection Support
On Wed, Nov 06, 2019 at 03:44:55PM +0800, Yang Weijiang wrote:
Ping...
Hi, Paolo,
Could you add comments on this patch serial? Thanks!
> EPT-Based Sub-Page write Protection(SPP) allows Virtual Machine Monitor(VMM)
> specify write-permission for guest physical memory at a sub-page(128 byte)
> granularity. When SPP works, HW enforces write-access check for sub-pages
> within a protected 4KB page.
>
> The feature targets to provide fine-grained memory protection for
> usages such as memory guard 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), and subpage permission vector is stored in the
> leaf entry of SPPT. The root page is referenced via a Sub-Page Permission
> Table Pointer (SPPTP) in VMCS.
>
> To enable SPP for guest memory, the guest page should be first mapped
> to a 4KB EPT entry, then set SPP bit 61 of the corresponding entry.
> While HW walks EPT, it traverses SPPT with the gpa to look up the sub-page
> permission vector within SPPT 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/2019/9/17/180
>
> Patch 1: Documentation for SPP and related API.
> Patch 2: Add control flags for Sub-Page Protection(SPP).
> Patch 3: Add SPP Table setup functions.
> Patch 4: Add functions to create/destroy SPP bitmap block.
> Patch 5: Introduce user-space SPP IOCTLs.
> Patch 6: Set up SPP paging table at vmentry/vmexit.
> Patch 7: Enable Lazy mode SPP protection.
> Patch 8: Handle SPP protected pages when VM memory changes.
> Patch 9: Add SPP protection check in emulation case.
>
>
> Change logs:
>
> V5 -> V6:
> 1. Added SPP protection patch for emulation cases per Jim's review.
> 2. Modified documentation and added API description per Jim's review.
> 3. Other minior changes suggested by Jim.
>
> V4 -> V5:
> 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 and related
> ioctls
> 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
> x86: spp: Introduce user-space SPP IOCTLs
> vmx: spp: Set up SPP paging table at vmentry/vmexit
> mmu: spp: Enable Lazy mode SPP protection
> mmu: spp: Handle SPP protected pages when VM memory changes
> x86: spp: Add SPP protection check in emulation.
>
> Documentation/virt/kvm/api.txt | 46 ++
> Documentation/virtual/kvm/spp_kvm.txt | 180 +++++++
> 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 | 649 ++++++++++++++++++++++++++
> arch/x86/kvm/vmx/spp.h | 28 ++
> arch/x86/kvm/vmx/vmx.c | 97 ++++
> arch/x86/kvm/x86.c | 87 ++++
> include/uapi/linux/kvm.h | 17 +
> 15 files changed, 1214 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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