linux-kernel - Re: [patch 0/7] x86/kvmclock: Remove memblock dependency and further cleanups

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Message-ID: <CAGM2reaKmu=h8QosuoJvJzzdTy2QfGRp9YxaKK-9UzpsfL-MoQ@mail.gmail.com>
Date:   Wed, 11 Jul 2018 22:12:32 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     tglx@...utronix.de
Cc:     LKML <linux-kernel@...r.kernel.org>, pbonzini@...hat.com,
        rkrcmar@...hat.com, peterz@...radead.org, jgross@...e.com,
        Steven Sistare <steven.sistare@...cle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>, x86@...nel.org,
        kvm@...r.kernel.org
Subject: Re: [patch 0/7] x86/kvmclock: Remove memblock dependency and further cleanups

> So this still will have some overhead when kvmclock is not in use, but
> bringing it down to zero would be a massive trainwreck and even more
> indirections.

Hi Thomas,

In my opinion, having kvmclock page in  __initdata for boot cpu, and
setup it in init_hypervisor_platform(). Later, switch to memblock
allocated memory in x86_init.hyper.guest_late_init() for all CPUs
would not be too bad, and might be even use fewer lines of code. In
addition, it won't have any overhead when kvm is not used.

Pavel