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 17:35:00 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Andrea Arcangeli <aarcange@...hat.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

On Tue, Sep 24, 2019 at 02:16:36AM +0200, Paolo Bonzini wrote:
> On 23/09/19 23:08, Andrea Arcangeli wrote:
> > The two most attractive options to me remains what I already have
> > implemented under #ifdef CONFIG_RETPOLINE with direct calls
> > (optionally replacing the "if" with a small "switch" still under
> > CONFIG_RETPOLINE if we give up the prioritization of the checks), or
> > the replacement of kvm_vmx_exit_handlers with a switch() as suggested
> > by Vitaly which would cleanup some code.
> > 
> > The intermediate solution that makes "const" work, has the cons of
> > forcing to parse EXIT_REASON_VMCLEAR and the other vmx exit reasons
> > twice, first through a pointer to function (or another if or switch
> > statement) then with a second switch() statement.
> 
> I agree.  I think the way Andrea did it in his patch may not the nicest
> but is (a bit surprisingly) the easiest and most maintainable.

Heh, which patch?  The original patch of special casing the high
priority exits?