linux-kernel - Re: [PATCH 15/17] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers

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Date:   Mon, 23 Sep 2019 20:38:21 -0400
From:   Andrea Arcangeli <aarcange@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Peter Xu <peterx@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/17] KVM: retpolines: x86: eliminate retpoline from
 vmx.c exit handlers

Hi Paolo,

On Tue, Sep 24, 2019 at 02:15:39AM +0200, Paolo Bonzini wrote:
> Do you really need that?  Why couldn't the handle_* functions simply be
> exported from nested.c to vmx.c?

I prefer the direct call too indeed.

If Sean doesn't want to export those generic names to the whole kernel
it would be enough to #include "nested.c" from vmx.c, and you'd still
have it private but with no additional checks and no additional extern
call. It's not like kvm-intel can be built without linking nested.o
anyway.

This overall is a C shortcoming of some sort if you've to resort to
#include "nested.c" to keep the function hidden in kvm-intel.o
despite it's implemented in two different object files. One should be
able to limit the scope of an extern function declaration per a group
of object files and to drop the declaration before linking that object
beyond that initial group.

Thanks,
Andrea