From: Gleb Natapov <gleb@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
"linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
mtosatti@redhat.com
Subject: Re: [PATCH-next] kvm: don't try to take mmu_lock while holding the main raw kvm_lock
Date: Thu, 27 Jun 2013 15:32:51 +0300 [thread overview]
Message-ID: <20130627123251.GO18508@redhat.com> (raw)
In-Reply-To: <51CC2D07.8080105@siemens.com>
On Thu, Jun 27, 2013 at 02:16:07PM +0200, Jan Kiszka wrote:
> On 2013-06-27 13:38, Paolo Bonzini wrote:
> > Il 27/06/2013 13:09, Gleb Natapov ha scritto:
> >> On Tue, Jun 25, 2013 at 06:34:03PM -0400, Paul Gortmaker wrote:
> >>> In commit e935b8372cf8 ("KVM: Convert kvm_lock to raw_spinlock"),
> >> I am copying Jan, the author of the patch. Commit message says:
> >> "Code under this lock requires non-preemptibility", but which code
> >> exactly is this? Is this still true?
> >
> > hardware_enable_nolock/hardware_disable_nolock does.
>
> IIRC, also the loop in kvmclock_cpufreq_notifier needs it because it
> reads the processor ID of the caller. That implies the caller cannot be
> preempted, but theses days a migration lock should be fine as well.
>
OK, adding Marcelo to the party. This code is called from cpufreq
notifier. I would expect that it will be called from the context that
prevents migration to another cpu.
--
Gleb.
next prev parent reply other threads:[~2013-06-27 12:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-25 22:34 [PATCH-next] kvm: don't try to take mmu_lock while holding the main raw kvm_lock Paul Gortmaker
2013-06-26 8:10 ` Paolo Bonzini
2013-06-26 18:11 ` [PATCH-next v2] " Paul Gortmaker
2013-06-26 21:59 ` Paolo Bonzini
2013-06-27 2:56 ` Paul Gortmaker
2013-06-27 10:22 ` Paolo Bonzini
2013-06-27 11:09 ` [PATCH-next] " Gleb Natapov
2013-06-27 11:38 ` Paolo Bonzini
2013-06-27 11:43 ` Gleb Natapov
2013-06-27 11:54 ` Paolo Bonzini
2013-06-27 12:16 ` Jan Kiszka
2013-06-27 12:32 ` Gleb Natapov [this message]
2013-06-27 13:00 ` Paolo Bonzini
2013-06-27 13:01 ` Paolo Bonzini
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