From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH 3/4] [PATCH] kvmclock: allow it to be turned off Date: Thu, 06 Mar 2008 09:01:51 -0300 Message-ID: <47CFDD2F.8010609@redhat.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> <47CF9393.6090407@qumranet.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: Avi Kivity Return-path: In-Reply-To: <47CF9393.6090407@qumranet.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 Avi Kivity wrote: > 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. dohh!! true /me ashamed. > 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. Apart from the fact that it will break every single guest out there, that's ok. As I said: these things are so early, that maybe we can pay this price. Your call. >> 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; >> >> > > ------------------------------------------------------------------------- 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/