Re: [PATCH v6 0/7] KVM: PKS Virtualization support

[Chenyi Qiang]

Kindly ping for comments.

On 2/21/2022 4:08 PM, Chenyi Qiang wrote:
> This patch series is based on top of v8 PKS core support kernel patchset:
> https://lore.kernel.org/lkml/20220127175505.851391-1-ira.weiny@xxxxxxxxx/
>
> Note: If you read the SDM section 4.6.1 and has some confusion about the
> statement of Data writes to supervisor-mode address:
>
>    If CR0.WP = 0, data may be written to any supervisor-mode address with
>    a protection key for which write access is permitted.
>
> Which may seems a little conflict with 4.6.2:
>
>    if WDi = 1, write accesses are not permitted if CR0.WP = 1. (If CR0.WP
>    = 0, IA32_PKRS.WDi does not affect write accesses to supervisor-mode
>    address with protection key i.)
>
> In fact, the statement in 4.6.1 doesn't say "a protection key with the
> appropriate WDi bit set." The reader should instead refer to Section
> 4.6.2 to find the definition of what that means. We will follow up
> this with someone internally to make it more clear in SDM.
>
> ---
>
> Protection Keys for Supervisor Pages(PKS) is a feature that extends the
> Protection Keys architecture to support thread-specific permission
> restrictions on supervisor pages.
>
> PKS works similar to an existing feature named PKU(protecting user pages).
> They both perform an additional check after normal paging permission
> checks are done. Access or Writes can be disabled via a MSR update
> without TLB flushes when permissions changes. If violating this
> addional check, #PF occurs and PFEC.PK bit will be set.
>
> PKS introduces MSR IA32_PKRS to manage supervisor protection key
> rights. The MSR contains 16 pairs of ADi and WDi bits. Each pair
> advertises on a group of pages with the same key which is set in the
> leaf paging-structure entries(bits[62:59]). Currently, IA32_PKRS is not
> supported by XSAVES architecture.
>
> This patchset aims to add the virtualization of PKS in KVM. It
> implemented PKS CPUID enumeration, vmentry/vmexit configuration, MSR
> exposure, nested supported etc. Currently, PKS is not yet supported for
> shadow paging.
>
> Detailed information about PKS can be found in the latest Intel 64 and
> IA-32 Architectures Software Developer's Manual.
>
> ---
>
> Changelogs:
>
> v5->v6
> - PKRS is preserved on INIT. Add the PKRS reset operation in kvm_vcpu_reset.
>    (Sean)
> - Track the pkrs as u32. Add the code WARN on bits 64:32 being set in VMCS field.
>    (Sean)
> - Adjust the MSR intercept and entry/exit control in VMCS according to
>    guest CPUID. This resolve the issue when userspace re-enable this feature.
>    (Sean)
> - Split VMX restriction on PKS support(entry/exit load controls) out of
>    common x86. And put tdp restriction together with PKU in common x86.
>    (Sean)
> - Thanks for Sean to revise the comments in mmu.c related to
>    update_pkr_bitmap, which make it more clear for pkr bitmask cache usage.
> - v5: https://lore.kernel.org/lkml/20210811101126.8973-1-chenyi.qiang@xxxxxxxxx/
>
> v4->v5
> - Make setting of MSR intercept/vmcs control bits not dependent on guest.CR4.PKS.
>    And set them if PKS is exposed to guest. (Suggested by Sean)
> - Add pkrs to standard register caching mechanism to help update
>    vcpu->arch.pkrs on demand. Add related helper functions. (Suggested by Sean)
> - Do the real pkrs update in VMCS field in vmx_vcpu_reset and
>    vmx_sync_vmcs_host_state(). (Sean)
> - Add a new mmu_role cr4_pks instead of smushing PKU and PKS together.
>    (Sean & Paolo)
> - v4: https://lore.kernel.org/lkml/20210205083706.14146-1-chenyi.qiang@xxxxxxxxx/
>
> v3->v4
> - Make the MSR intercept and load-controls setting depend on CR4.PKS value
> - shadow the guest pkrs and make it usable in PKS emultion
> - add the cr4_pke and cr4_pks check in pkr_mask update
> - squash PATCH 2 and PATCH 5 to make the dependencies read more clear
> - v3: https://lore.kernel.org/lkml/20201105081805.5674-1-chenyi.qiang@xxxxxxxxx/
>
> v2->v3:
> - No function changes since last submit
> - rebase on the latest PKS kernel support:
>    https://lore.kernel.org/lkml/20201102205320.1458656-1-ira.weiny@xxxxxxxxx/
> - add MSR_IA32_PKRS to the vmx_possible_passthrough_msrs[]
> - RFC v2: https://lore.kernel.org/lkml/20201014021157.18022-1-chenyi.qiang@xxxxxxxxx/
>
> v1->v2:
> - rebase on the latest PKS kernel support:
>    https://github.com/weiny2/linux-kernel/tree/pks-rfc-v3
> - add a kvm-unit-tests for PKS
> - add the check in kvm_init_msr_list for PKRS
> - place the X86_CR4_PKS in mmu_role_bits in kvm_set_cr4
> - add the support to expose VM_{ENTRY, EXIT}_LOAD_IA32_PKRS in nested
>    VMX MSR
> - RFC v1: https://lore.kernel.org/lkml/20200807084841.7112-1-chenyi.qiang@xxxxxxxxx/
>
> ---
>
> Chenyi Qiang (7):
>    KVM: VMX: Introduce PKS VMCS fields
>    KVM: VMX: Add proper cache tracking for PKRS
>    KVM: X86: Expose IA32_PKRS MSR
>    KVM: MMU: Rename the pkru to pkr
>    KVM: MMU: Add support for PKS emulation
>    KVM: VMX: Expose PKS to guest
>    KVM: VMX: Enable PKS for nested VM
>
>   arch/x86/include/asm/kvm_host.h |  17 ++++--
>   arch/x86/include/asm/vmx.h      |   6 ++
>   arch/x86/kvm/cpuid.c            |  13 ++--
>   arch/x86/kvm/kvm_cache_regs.h   |   7 +++
>   arch/x86/kvm/mmu.h              |  27 +++++----
>   arch/x86/kvm/mmu/mmu.c          | 101 ++++++++++++++++++++------------
>   arch/x86/kvm/vmx/capabilities.h |   6 ++
>   arch/x86/kvm/vmx/nested.c       |  38 +++++++++++-
>   arch/x86/kvm/vmx/vmcs.h         |   1 +
>   arch/x86/kvm/vmx/vmcs12.c       |   2 +
>   arch/x86/kvm/vmx/vmcs12.h       |   4 ++
>   arch/x86/kvm/vmx/vmx.c          |  92 ++++++++++++++++++++++++++---
>   arch/x86/kvm/vmx/vmx.h          |   7 ++-
>   arch/x86/kvm/x86.c              |  10 +++-
>   arch/x86/kvm/x86.h              |   8 +++
>   arch/x86/mm/pkeys.c             |   6 ++
>   include/linux/pkeys.h           |   6 ++
>   17 files changed, 280 insertions(+), 71 deletions(-)