linux-kernel - Re: mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")

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Message-ID: <CADVatmNrdRJB+xcGSOdCf86ZuTrUATnpOhxSeA5HkUR9RT89+A@mail.gmail.com>
Date:   Wed, 13 Jul 2022 14:34:35 +0100
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>, Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent
 guest RSB poisoning attacks with eIBRS")

On Wed, Jul 13, 2022 at 1:22 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Wed, Jul 13, 2022 at 01:35:22PM +0200, Peter Zijlstra wrote:
> > On Wed, Jul 13, 2022 at 12:28:38PM +0100, Sudip Mukherjee (Codethink) wrote:
> > > Hi All,
> > >
> > > The latest mainline kernel branch fails to build for x86_64 allmodconfig
> > > with clang and the error is:
> > >

<snip>

> >  extern u64 spec_ctrl_current(void);
> >
>
> I hate headers...

very short commit message :D

>
> ---
> diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
> index bb05ed4f46bd..cbc3b8348939 100644
> --- a/arch/x86/include/asm/nospec-branch.h
> +++ b/arch/x86/include/asm/nospec-branch.h
> @@ -280,7 +280,6 @@ static inline void indirect_branch_prediction_barrier(void)
>
>  /* The Intel SPEC CTRL MSR base value cache */
>  extern u64 x86_spec_ctrl_base;
> -extern u64 x86_spec_ctrl_current;
>  extern void write_spec_ctrl_current(u64 val, bool force);
>  extern u64 spec_ctrl_current(void);
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index be7c19374fdd..b64512978534 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6831,6 +6831,8 @@ void noinstr vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
>         }
>  }
>
> +DECLARE_PER_CPU(u64, x86_spec_ctrl_current);
> +
>  void noinstr vmx_spec_ctrl_restore_host(struct vcpu_vmx *vmx,
>                                         unsigned int flags)
>  {

The build failure is fixed with this change. Thanks.


-- 
Regards
Sudip