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Re: [PATCH v2 00/12] x86: major paravirt cleanup
- To: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
- From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- Date: Wed, 16 Dec 2020 18:58:28 +0100
- Cc: Jürgen Groß <jgross@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, linux-hyperv@xxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx, luto@xxxxxxxxxx, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Deep Shah <sdeep@xxxxxxxxxx>, "VMware, Inc." <pv-drivers@xxxxxxxxxx>, "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>, Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>, Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>, Wei Liu <wei.liu@xxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Sean Christopherson <sean.j.christopherson@xxxxxxxxx>, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>, Wanpeng Li <wanpengli@xxxxxxxxxxx>, Jim Mattson <jmattson@xxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>, Juri Lelli <juri.lelli@xxxxxxxxxx>, Vincent Guittot <vincent.guittot@xxxxxxxxxx>, Dietmar Eggemann <dietmar.eggemann@xxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Ben Segall <bsegall@xxxxxxxxxx>, Mel Gorman <mgorman@xxxxxxx>, Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
- Delivery-date: Wed, 16 Dec 2020 17:59:24 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Wed, Dec 16, 2020 at 10:56:05AM -0600, Josh Poimboeuf wrote:
> On Wed, Dec 16, 2020 at 09:40:59AM +0100, Peter Zijlstra wrote:
> > > Could we make it easier by caching the shared
> > > per-alt-group CFI state somewhere along the way?
> >
> > Yes, but when I tried it grew the code required. Runtime costs would be
> > less, but I figured that since alternatives are typically few and small,
> > that wasn't a real consideration.
>
> Aren't alternatives going to be everywhere now with paravirt using them?
What I meant was, they're either 2-3 wide and only a few instructions
long. Which greatly bounds the actual complexity of the algorithm,
however daft.
> > No real objection, I just didn't do it because 1) it works, and 2) even
> > moar lines.
>
> I'm kind of surprised it would need moar lines. Let me play around with
> it and maybe I'll come around ;-)
Please do, it could be getting all the niggly bits right exhausted my
brain enough to miss the obvious ;-)
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