Re: [PATCH v1 0/6] LASS KVM virtualization support

[Zeng Guang]

On 6/5/2023 9:39 AM, Binbin Wu wrote:
> On 6/1/2023 10:23 PM, Zeng Guang wrote:
> > Subject:
> > [PATCH v1 0/6] LASS KVM virtualization support
> > From:
> > Zeng Guang <guang.zeng@xxxxxxxxx>
> > Date:
> > 6/1/2023, 10:23 PM
> >
> > To:
> > Paolo Bonzini <pbonzini@xxxxxxxxxx>, Sean Christopherson
> > <seanjc@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar
> > <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen
> > <dave.hansen@xxxxxxxxxxxxxxx>, H Peter Anvin <hpa@xxxxxxxxx>,
> > kvm@xxxxxxxxxxxxxxx
> > CC:
> > x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Zeng Guang
> > <guang.zeng@xxxxxxxxx>
> >
> >
> > Linear Address Space Separation (LASS)[1] is an independent mechanism
> > that enforces the mode-based protections on any access to a linear
> > address.
> >
> > Based on a linear-address organization, the 64-bit canonical linear
> > address space is partitioned into two halves: all linear addresses
> > whose most significant bit is 0 are user space addresses, while linear
> > addresses whose most significant bit is 1 are supervisor space address.
> >
> > LASS aims to prevent any attempt to probe supervisor space addresses by
> > user mode, and likewise stop any attempt to access (if SMAP enabled) or
> > execute user space addresses from supervisor mode.
> >
> > When platform has LASS capability, KVM requires to expose this feature
> > to guest VM enumerated by CPUID.(EAX=07H.ECX=1):EAX.LASS[bit 6], and
> > allow guest to enable it via CR4.LASS[bit 27] on demand. For instruction
> > executed in the guest directly, hardware will perform the check. But KVM
> > also needs to behave same as hardware to apply LASS to kinds of guest
> > memory accesses when emulating privileged instructions by software.
> Not just privileged instructions, e.g. MMIO access instructions.
OK. I'll revise it.
> > KVM will take following LASS voilations check on emulation path.
> /s/voilations/violations
Thanks.
> > User-mode access to supervisor space address:
> >           LA[bit 63] && (CPL == 3)
> > Supervisor-mode access to user space address:
> >           Instruction fetch: !LA[bit 63] && (CPL < 3)
> >           Data access: !LA[bit 63] && (CR4.SMAP==1) && ((RFLAGS.AC == 0 &&
> >                        CPL < 3) || Implicit supervisor access)
> >
> > This patch series provide a LASS KVM solution.
> >
> > We tested the basic function of LASS virtualization including LASS
> > enumeration and enabling in non-root and nested environment. As KVM
> > unittest framework is not compatible to LASS rule, we use kernel module
> > and application test to emulate LASS violation instead. With KVM forced
> > emulation mechanism, we also verified the LASS functionality on some
> > emulation path with instruction fetch and data access to have same
> > behavior as hardware.
> >
> > [1] Intel ISEhttps://cdrdv2.intel.com/v1/dl/getContent/671368
> > Chapter Linear Address Space Separation (LASS)
> >
> > ------------------------------------------------------
> >
> > v0->v1
> > 1. Adapt to new __linearize() API
> > 2. Function refactor of vmx_check_lass()
> > 3. Refine commit message to be more precise
> > 4. Drop LASS kvm cap detection depending
> >      on hardware capability
> >
> >
> > Binbin Wu (1):
> >     KVM: x86: Consolidate flags for __linearize()
> >
> > Zeng Guang (5):
> >     KVM: x86: Virtualize CR4.LASS
> >     KVM: VMX: Add new ops in kvm_x86_ops for LASS violation check
> >     KVM: x86: Add emulator helper for LASS violation check
> >     KVM: x86: LASS protection on KVM emulation
> >     KVM: x86: Advertise LASS CPUID to user space
> >
> >    arch/x86/include/asm/kvm-x86-ops.h |  3 +-
> >    arch/x86/include/asm/kvm_host.h    |  4 ++-
> >    arch/x86/kvm/cpuid.c               |  5 ++-
> >    arch/x86/kvm/emulate.c             | 47 +++++++++++++++++++++++-----
> >    arch/x86/kvm/kvm_emulate.h         |  6 ++++
> >    arch/x86/kvm/vmx/nested.c          |  3 ++
> >    arch/x86/kvm/vmx/sgx.c             |  4 +++
> >    arch/x86/kvm/vmx/vmx.c             | 50 ++++++++++++++++++++++++++++++
> >    arch/x86/kvm/vmx/vmx.h             |  2 ++
> >    arch/x86/kvm/x86.c                 | 12 +++++++
> >    arch/x86/kvm/x86.h                 |  2 ++
> >    11 files changed, 126 insertions(+), 12 deletions(-)
> >
> > -- 2.27.0