From: Paolo Bonzini <pbonzini@redhat.com>
To: Christoffer Dall <christofferdall@gmail.com>
Cc: Jintack Lim <jintack@cs.columbia.edu>,
KVM General <kvm@vger.kernel.org>,
Shih-Wei Li <shihwei@cs.columbia.edu>
Subject: Re: rdtsc() in kvm-unit-tests on x86
Date: Mon, 10 Aug 2015 15:58:08 +0200 [thread overview]
Message-ID: <55C8ADF0.8040204@redhat.com> (raw)
In-Reply-To: <CAEDV+g+hwvSqWUjNAKcJVcTf-6vXx5j+YiN=aaYKJbo=pmWcEw@mail.gmail.com>
On 10/08/2015 11:42, Christoffer Dall wrote:
>
> Thanks for the reply.
>
> On this note, is there an easy mechanism on x86 to obtain a TSC which is
> synchronized across PCPUs and between the host and the guest?
>
> We can use the physical arch timer counter on arm64, but I'm not sure if
> there's something similar on x86?
Yes, you just use the TSC. :) However, you first have to check that the
TSC is consistent across CPUs. On older machines it's not, but the
kernel can detect it.
Paolo
> This is useful to trace the flow of events over an SMP system in detail.
next prev parent reply other threads:[~2015-08-10 13:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-07 19:19 rdtsc() in kvm-unit-tests on x86 Jintack Lim
2015-08-10 9:02 ` Paolo Bonzini
[not found] ` <CAEDV+g+hwvSqWUjNAKcJVcTf-6vXx5j+YiN=aaYKJbo=pmWcEw@mail.gmail.com>
2015-08-10 13:58 ` Paolo Bonzini [this message]
2015-08-10 14:14 ` Jintack Lim
2015-08-10 14:47 ` Paolo Bonzini
2015-08-10 15:38 ` Jintack Lim
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