From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH RFC V2 3/6] xen: Force-enable relevant MSR events; optimize the number of sent MSR events Date: Fri, 11 Jul 2014 19:19:21 +0100 Message-ID: <53C02AA9.1080307@citrix.com> References: <1405093418-23481-1-git-send-email-rcojocaru@bitdefender.com> <1405093418-23481-3-git-send-email-rcojocaru@bitdefender.com> <53C018FB.3080307@citrix.com> <53C02859.10208@bitdefender.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53C02859.10208@bitdefender.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: Razvan Cojocaru , xen-devel@lists.xen.org Cc: mdontu@bitdefender.com, tim@xen.org, JBeulich@suse.com List-Id: xen-devel@lists.xenproject.org On 11/07/14 19:09, Razvan Cojocaru wrote: > On 07/11/2014 08:03 PM, Andrew Cooper wrote: >> On 11/07/14 16:43, Razvan Cojocaru wrote: >>> Vmx_disable_intercept_for_msr() will now refuse to disable interception of >>> MSRs needed for memory introspection. It is not possible to gate this on >>> mem_access being active for the domain, since by the time mem_access does >>> become active the interception for the interesting MSRs has already been >>> disabled (vmx_disable_intercept_for_msr() runs very early on). >>> >>> Changes since V1: >>> - Replaced printk() with gdprintk(XENLOG_DEBUG, ...). >>> >>> Signed-off-by: Razvan Cojocaru >>> --- >>> xen/arch/x86/hvm/vmx/vmcs.c | 18 ++++++++++++++++++ >>> 1 file changed, 18 insertions(+) >>> >>> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c >>> index 8ffc562..35fcfcc 100644 >>> --- a/xen/arch/x86/hvm/vmx/vmcs.c >>> +++ b/xen/arch/x86/hvm/vmx/vmcs.c >>> @@ -700,6 +700,24 @@ void vmx_disable_intercept_for_msr(struct vcpu *v, u32 msr, int type) >>> if ( msr_bitmap == NULL ) >>> return; >>> >>> + /* Filter out MSR-s needed for memory introspection */ >>> + switch ( msr ) >> This absolutely must be gated on mem_events being enabled for the domain. >> >> It is too much of a performance penalty to apply to domains which are >> not being introspected. > I understand, but it really runs very early on, and the mem_event part > comes in after the MSR interception is disabled. This effectively > renders a lot of memory introspection functionality useless. In which case the hypercall which enables mem_event needs to prod the vmcs state an explicitly enable intercepts for these MSRs. (and conversly re-disables intercepts if mem_events are disabled) You can probably get away with hvm_funcs to enable and disable mem events. ~Andrew