linux-kernel - Re: [RESEND PATCH v13 00/11] Introduce support for guest CET feature

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Date:   Thu, 23 Jul 2020 11:17:49 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Yang Weijiang <weijiang.yang@...el.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, pbonzini@...hat.com,
        jmattson@...gle.com, yu.c.zhang@...ux.intel.com
Subject: Re: [RESEND PATCH v13 00/11] Introduce support for guest CET feature

On Wed, Jul 22, 2020 at 12:48:05PM -0700, Sean Christopherson wrote:
> On Thu, Jul 16, 2020 at 11:16:16AM +0800, Yang Weijiang wrote:
> > Control-flow Enforcement Technology (CET) provides protection against
> > Return/Jump-Oriented Programming (ROP/JOP) attack. There're two CET
> > sub-features: Shadow Stack (SHSTK) and Indirect Branch Tracking (IBT).
> > SHSTK is to prevent ROP programming and IBT is to prevent JOP programming.
> > 
> > Several parts in KVM have been updated to provide VM CET support, including:
> > CPUID/XSAVES config, MSR pass-through, user space MSR access interface, 
> > vmentry/vmexit config, nested VM etc. These patches have dependency on CET
> > kernel patches for xsaves support and CET definitions, e.g., MSR and related
> > feature flags.
> > 
> > CET kernel patches are here:
> > https://lkml.kernel.org/r/20200429220732.31602-1-yu-cheng.yu@intel.com
> > 
> > v13:
> > - Added CET definitions as a separate patch to facilitate KVM test.
> 
> What I actually want to do is pull in actual kernel patches themselves so
> that we can upstream KVM support without having to wait for the kernel to
> sort out the ABI, which seems like it's going to drag on.
That's an innovative idea and beyond my imagination, great!:-)
> 
> I was thinking that we'd only need the MSR/CR4/CPUID definitions, but forgot
> that KVM also needs XSAVES context switching, so it's not as simple as I was
> thinking.  It's still relatively simple, but it means there would be
> functional changes in the kernel.
> 
> I'll respond to the main SSP series to pose the question of taking the two
> small-ish kernel patches through the KVM tree.
> 
> >  arch/x86/include/asm/kvm_host.h      |   4 +-
> >  arch/x86/include/asm/vmx.h           |   8 +
> >  arch/x86/include/uapi/asm/kvm.h      |   1 +
> >  arch/x86/include/uapi/asm/kvm_para.h |   7 +-
> >  arch/x86/kvm/cpuid.c                 |  28 ++-
> >  arch/x86/kvm/vmx/capabilities.h      |   5 +
> >  arch/x86/kvm/vmx/nested.c            |  34 ++++
> >  arch/x86/kvm/vmx/vmcs12.c            | 267 ++++++++++++++++-----------
> >  arch/x86/kvm/vmx/vmcs12.h            |  14 +-
> >  arch/x86/kvm/vmx/vmx.c               | 262 +++++++++++++++++++++++++-
> >  arch/x86/kvm/x86.c                   |  53 +++++-
> >  arch/x86/kvm/x86.h                   |   2 +-
> >  include/linux/kvm_host.h             |  32 ++++
> >  13 files changed, 590 insertions(+), 127 deletions(-)
> 
> I have quite a few comments/changes (will respond to individual patches),
> but have done all the updates/rework and, assuming I haven't broken things,
> we're nearing the point where I can carry this and push it past the finish
> line, e.g. get acks from tip/x86 maintainers for the kernel patches and
> send a pull request to Paolo.
> 
> I pushed the result to:
> 
>   https://github.com/sean-jc/linux/releases/tag/kvm-cet-v14-rc1
> 
> can you please review and test?  If everything looks good, I'll post v14.
> If not, I'll work offline with you to get it into shape.
>
Thanks a lot for the efforts! I'll review and test the new patches and
let you know the status.

> Thanks!