From mboxrd@z Thu Jan 1 00:00:00 1970 From: Razvan Cojocaru Subject: Re: [PATCH RFC V5 3/5] xen: Force-enable relevant MSR events; optimize the number of sent MSR events Date: Mon, 11 Aug 2014 11:57:36 +0300 Message-ID: <53E88580.4070608@bitdefender.com> References: <1407340738-3374-1-git-send-email-rcojocaru@bitdefender.com> <1407340738-3374-3-git-send-email-rcojocaru@bitdefender.com> <53E4FC26020000780002AA23@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53E4FC26020000780002AA23@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: kevin.tian@intel.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, andrew.cooper3@citrix.com, eddie.dong@intel.com, xen-devel@lists.xen.org, jun.nakajima@intel.com, ian.jackson@eu.citrix.com List-Id: xen-devel@lists.xenproject.org On 08/08/2014 05:34 PM, Jan Beulich wrote: >>>> On 06.08.14 at 17:58, wrote: >> --- a/xen/arch/x86/mm/mem_event.c >> +++ b/xen/arch/x86/mm/mem_event.c >> @@ -600,6 +600,9 @@ int mem_event_domctl(struct domain *d, xen_domctl_mem_event_op_t *mec, >> rc = mem_event_enable(d, mec, med, _VPF_mem_access, >> HVM_PARAM_ACCESS_RING_PFN, >> mem_access_notification); >> + >> + if ( rc == 0 && hvm_funcs.enable_intro_msr_interception ) >> + hvm_funcs.enable_intro_msr_interception(d); > > Isn't the sequence of operations wrong here (leaving a window in > time where mem events are already enabled but the necessary MSRs > aren't being intercepted yet? Or was it that guests are being paused > while all this takes place? I've looked into how this is implemented on the libxc side, and it would appear that xc_mem_event_enable() (in xc_mem_event.c) does explicitly pause the domain before calling xc_mem_event_control() (which ends up in the code above), so it should not be a problem. Thanks, Razvan Cojocaru