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

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Date:   Tue, 6 Jun 2023 10:40:39 +0800
From:   Zeng Guang <guang.zeng@...el.com>
To:     Binbin Wu <binbin.wu@...ux.intel.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        H Peter Anvin <hpa@...or.com>,
        Borislav Petkov <bp@...en8.de>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 0/6] LASS KVM virtualization support


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@...el.com>
>> Date:
>> 6/1/2023, 10:23 PM
>>
>> To:
>> Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson
>> <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
>> CC:
>> x86@...nel.org, linux-kernel@...r.kernel.org, Zeng Guang
>> <guang.zeng@...el.com>
>>
>>
>> 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