linux-kernel - Re: [Xen-devel] [PATCH 00/13] x86/paravirt: Make pv ops code generation more closely match reality

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Message-ID: <20171006143606.tbv4y2te6jvqoach@treble>
Date:   Fri, 6 Oct 2017 09:36:06 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     x86@...nel.org, Juergen Gross <jgross@...e.com>,
        Rusty Russell <rusty@...tcorp.com.au>,
        xen-devel@...ts.xenproject.org,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org,
        Sasha Levin <alexander.levin@...izon.com>,
        Chris Wright <chrisw@...s-sol.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        live-patching@...r.kernel.org, Alok Kataria <akataria@...are.com>,
        virtualization@...ts.linux-foundation.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [Xen-devel] [PATCH 00/13] x86/paravirt: Make pv ops code
 generation more closely match reality

On Fri, Oct 06, 2017 at 09:35:16AM +0200, Vitaly Kuznetsov wrote:
> Josh Poimboeuf <jpoimboe@...hat.com> writes:
> 
> > - For the most common runtime cases (everything except Xen and vSMP),
> >   vmlinux disassembly now matches what the actual runtime code looks
> >   like.  This improves debuggability and kernel developer sanity (a
> >   precious resource).
> >
> > ...
> >
> > - It's hopefully a first step in simplifying paravirt patching by
> >   getting rid of .parainstructions, pv ops, and apply_paravirt()
> >   completely.  (I think Xen can be changed to set CPU feature bits to
> >   specify which ops it needs during early boot, then those ops can be
> >   patched in using early alternatives.)
> 
> JFYI starting 4.14 Xen PV is not the only user of pv_mmu_ops, Hyper-V
> uses it for TLB shootdown now.

Yeah, I saw that.  It should be fine because the pv_alternatives get
patched before the Hyper-V code sets up pv_mmu_ops.

-- 
Josh