From mboxrd@z Thu Jan 1 00:00:00 1970 From: Razvan Cojocaru Subject: Re: Should hvm_hw_cpu's sysenter_eip always be zero after xc_domain_hvm_getcontext_partial()? Date: Fri, 31 Jul 2015 18:30:08 +0300 Message-ID: <55BB9480.1020200@bitdefender.com> References: <55BB8D9A.2070705@bitdefender.com> <55BB9094.30703@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55BB9094.30703@citrix.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: Andrew Cooper , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org Thanks for the quick reply! On 07/31/2015 06:13 PM, Andrew Cooper wrote: >> Looking in the code, the only two __vmwrite(GUEST_SYSENTER_EIP, ...) >> calls occur in xen/arch/x86/hvm/vmx/vmx.c. One is in >> vmx_msr_write_intercept(), but adding a printk() just after produces no >> output after starting and stopping a guest. > > Write interception for that MSR is disabled (if the hardware supports > disabling interception) because it is not interesting. > > You can re-enable interception by commenting out the appropriate > vmx_disable_intercept_for_msr() line in construct_vmcs() It shouldn't be disabled, it's in the vmx_introspection_force_enabled_msrs[] list and I'm testing it with memory introspection. >> The other is in vmx_vmcs_restore(), which seems to dutifully restore the >> never-set value of zero after a save. >> >> So this doesn't seem to be actually initialized anywhere. Could somebody >> please recommend the best place to initialize it, and the best value to >> initialize it with? Or maybe you could point out what I'm missing, if >> that's the case? > > Are you certain that the guest is actually setting it? If the guest > never sets it in the first place, 0 will be the expected value. That might be it, I'll need to look closer. Thanks, Razvan