[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RFC 3/9] xen: Force-enable relevant MSR events; optimize the number of sent MSR events
>>> On 09.07.14 at 10:02, <rcojocaru@xxxxxxxxxxxxxxx> wrote: > On 07/02/2014 06:43 PM, Jan Beulich wrote: >>>>> On 02.07.14 at 17:35, <andrew.cooper3@xxxxxxxxxx> wrote: >>> On 02/07/14 14:33, Razvan Cojocaru wrote: >>>> @@ -700,6 +700,25 @@ void vmx_disable_intercept_for_msr(struct vcpu *v, >>>> u32 > msr, int type) >>>> if ( msr_bitmap == NULL ) >>>> return; >>>> >>>> + /* Filter out MSR-s needed by the memory introspection engine */ >>>> + switch ( msr ) >>>> + { >>>> + case MSR_IA32_SYSENTER_EIP: >>>> + case MSR_IA32_SYSENTER_ESP: >>>> + case MSR_IA32_SYSENTER_CS: >>>> + case MSR_IA32_MC0_CTL: >>>> + case MSR_STAR: >>>> + case MSR_LSTAR: >>>> + >>> >>> Given the performance implications of forcing interception of these >>> MSRs, it would be gated on mem_access being active for the domain. >> >> Absolutely. > > Unfortunately the call to vmx_disable_intercept_for_msr() happens _very_ > early, and by the time our application gets to enable mem_access on the > domain, the interception for these MSRs has already been disabled, with > unacceptable consequences. > > I've tested this with an "if ( > mem_event_check_ring(&d->mem_event->access) )" test. > > Also, ideally we'd like to be able to start monitoring an already > started domain, and in that case the mem_access test would be useless > even considering a workaround for the case above. All understood, but not penalizing non-monitored VMs has certainly higher priority. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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