From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 3/4] [PATCH] kvmclock: allow it to be turned off Date: Thu, 06 Mar 2008 08:47:47 +0200 Message-ID: <47CF9393.6090407@qumranet.com> References: <1204742492-20738-1-git-send-email-gcosta@redhat.com> <1204742492-20738-2-git-send-email-gcosta@redhat.com> <1204742492-20738-3-git-send-email-gcosta@redhat.com> <1204742492-20738-4-git-send-email-gcosta@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, chrisw@sous-sol.org To: Glauber Costa Return-path: In-Reply-To: <1204742492-20738-4-git-send-email-gcosta@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Glauber Costa wrote: > Use the lower 3 lower bits of the system time msr to turn off the clock. > This means that all clock registration has to be aligned in a 4-byte boundary > > 3 bits -> 8 bytes. How about just using just bit 0 as an enable bit (not a disable bit). That means the default value of zero means the clock is disabled, and that we have a couple of more bits to enable future features. > Signed-off-by: Glauber Costa > --- > arch/x86/kvm/x86.c | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 6abd784..7ce14ce 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -591,6 +591,11 @@ int kvm_set_msr_common(struct kvm_vcpu * > if (vcpu->arch.time_page) > kvm_release_page_dirty(vcpu->arch.time_page); > > + /* 4-byte unaligned accesses are invalid */ > + if (data & 0x7) { > + vcpu->arch.time_page = NULL; > + break; > + } > vcpu->arch.time = data & PAGE_MASK; > vcpu->arch.time_offset = data & ~PAGE_MASK; > > -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/