linux-kernel - Re: [PATCH v2 0/8] LASS KVM virtualization support

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Message-ID: <69afdc99-df5d-678e-5a63-2ef33c607d3a@intel.com>
Date:   Wed, 19 Jul 2023 11:05:40 +0800
From:   Zeng Guang <guang.zeng@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        H Peter Anvin <hpa@...or.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/8] LASS KVM virtualization support

Please ignore this patch set as I posted wrong one by mistake.
I will submit the correct patch series soon. Sorry for bothering.

On 7/18/2023 9:18 PM, Zeng, Guang wrote:
> Linear Address Space Separation (LASS)[1] is a new mechanism that
> enforces the same mode-based protections as paging, i.e. SMAP/SMEP
> but without traversing the paging structures. Because the protections
> enforced by LASS are applied before paging, "probes" by malicious
> software will provide no paging-based timing information.
>
> Based on a linear-address organization, LASS partitions 64-bit linear
> address space into two halves, user-mode address (LA[bit 63]=0) and
> supervisor-mode address (LA[bit 63]=1).
>
> LASS aims to prevent any attempt to probe supervisor-mode addresses by
> user mode, and likewise stop any attempt to access (if SMAP enabled) or
> execute user-mode 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 instructions by software.
>
> KVM will take following LASS violations check on emulation path.
> 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 and depends on kernel
> enabling that can be found at
> https://lore.kernel.org/all/20230609183632.48706-1-alexander.shishkin@linux.intel.com/
>
> 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.
>
> How to extend kselftest to support LASS is under investigation and
> experiment.
>
> [1] Intel ISE https://cdrdv2.intel.com/v1/dl/getContent/671368
> Chapter Linear Address Space Separation (LASS)
>
> ------------------------------------------------------------------------
>
> v1->v2
> 1. refactor and optimize the interface of instruction emulation
>     by introducing new set of operation type definition prefixed with
>     "X86EMUL_F_" to distinguish access.
> 2. reorganize the patch to make each area of KVM better isolated.
> 3. refine LASS violation check design with consideration of wraparound
>     access across address space boundary.
>
> 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 (4):
>    KVM: x86: Consolidate flags for __linearize()
>    KVM: x86: Use a new flag for branch instructions
>    KVM: x86: Add an emulation flag for implicit system access
>    KVM: x86: Add X86EMUL_F_INVTLB and pass it in em_invlpg()
>
> Zeng Guang (4):
>    KVM: emulator: Add emulation of LASS violation checks on linear
>      address
>    KVM: VMX: Implement and apply vmx_is_lass_violation() for LASS
>      protection
>    KVM: x86: Virtualize CR4.LASS
>    KVM: x86: Advertise LASS CPUID to user space
>
>   arch/x86/include/asm/kvm-x86-ops.h |  3 ++-
>   arch/x86/include/asm/kvm_host.h    |  5 +++-
>   arch/x86/kvm/cpuid.c               |  5 ++--
>   arch/x86/kvm/emulate.c             | 37 ++++++++++++++++++++---------
>   arch/x86/kvm/kvm_emulate.h         |  9 +++++++
>   arch/x86/kvm/vmx/nested.c          |  3 ++-
>   arch/x86/kvm/vmx/sgx.c             |  4 ++++
>   arch/x86/kvm/vmx/vmx.c             | 38 ++++++++++++++++++++++++++++++
>   arch/x86/kvm/vmx/vmx.h             |  3 +++
>   arch/x86/kvm/x86.c                 | 10 ++++++++
>   arch/x86/kvm/x86.h                 |  2 ++
>   11 files changed, 102 insertions(+), 17 deletions(-)
>