From: Paolo Bonzini <pbonzini@redhat.com>
To: Santosh Shukla <sshukla@mvista.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
Marcelo Tosatti <mtosatti@redhat.com>,
Gleb Natapov <gleb@kernel.org>, kvm list <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Cleaning up the KVM clock
Date: Tue, 23 Dec 2014 11:25:08 +0100 [thread overview]
Message-ID: <54994304.1060808@redhat.com> (raw)
In-Reply-To: <CAAyOgsbNsDmPGzJcEuYExaswWaQoLHzkMVd+r6r-8jnGc00yTA@mail.gmail.com>
On 23/12/2014 11:23, Santosh Shukla wrote:
>
>
> No. kvm_guest_time_update is called by vcpu_enter_guest, while the vCPU
> is not running, so it's entirely atomic from the point of view of
> the guest.
>
>
> Then checking odd value for version field (at guest side: function
> pvclock_clocksource_read / pvclock_read_flag) is redundant considering
> that kvm_guest_time_update incremented by 2.
The code is common to Xen and KVM. Xen uses seqlock semantics. The
cost of one AND is not detectable.
Paolo
next prev parent reply other threads:[~2014-12-23 10:25 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-21 3:31 Cleaning up the KVM clock Andy Lutomirski
2014-12-22 10:15 ` Paolo Bonzini
2014-12-22 13:34 ` Marcelo Tosatti
2014-12-22 14:09 ` Marcelo Tosatti
2014-12-22 16:03 ` Andy Lutomirski
2014-12-22 22:47 ` Paolo Bonzini
2014-12-22 22:49 ` Paolo Bonzini
2014-12-22 23:00 ` Andy Lutomirski
2014-12-22 23:14 ` Paolo Bonzini
2014-12-22 23:31 ` Andy Lutomirski
[not found] ` <CAAyOgsbNsDmPGzJcEuYExaswWaQoLHzkMVd+r6r-8jnGc00yTA@mail.gmail.com>
2014-12-23 10:25 ` Paolo Bonzini [this message]
2014-12-22 13:38 ` Marcelo Tosatti
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