Hi: I intend to use RDTSC to make some time tests in Xen guest WinXP. However, from Intel Developer''s Manual I noticed that RDTSC will cause VMExit if "RETSC exiting" VM-Execution control field is 1. So I wonder: How to query VM-Execution control field in a programmable way? BTW: On Intel Developer''s Manual, it mentioned a method using IA32_VMX_PROCBASED_CTLS MSR, but this is just to report which bits can be set on processor-based VM-EXECUTION controls, rather than telling you the content of this structure. Thanks! _________________________________________________________________ 微软地图率先推出跨城市多点驾车路线查询! http://ditu.live.com/?form=MRAHAB&rtp=pos.30.454167_116.308611_%E5%A4%AA%E6%B9%96__~pos.29.554046_115.983427_%E5%BA%90%E5%B1%B1__~pos.29.116111_110.478889_%E5%BC%A0%E5%AE%B6%E7%95%8C__&rtop=0~0~0&encType=1 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
XuNanxuan
2008-Dec-05 06:03 UTC
RE: [Xen-devel] Question about time measure in Guest Windows
Thanks for your suggest! But I have a further question about this issue: In my tests, I need to use some other instructions like RDTSC that may cause VMExit conditionally, one example is WBINVD which is another bit in VM-execution control field. From your advice, can I say that I can ignore all the bits of VM-execution control field in Xen? Otherwise, How to query VM-Execution control field in a programmable way? Thanks! Nanxuan> Date: Thu, 4 Dec 2008 07:10:36 -0800> From: dan.magenheimer@oracle.com> To: nanxuan_xu@live.cn> Subject: RE: [Xen-devel] Question about time measure in Guest Windows> > "RDTSC exiting VM execution control field" is available so that> a hypervisor can trap ALL guest uses of the RDTSC instruction.> Xen does not currently use this, so you can use RDTSC in a Xen> Windows guest without worrying about it.> > HOWEVER, be aware that on many SMP machines, the TSC is not> synchronized between processors and your guest may move between> processors without its knowledge. So two consecutive reads> of TSC by a guest may appear as if TSC is going backwards or> jumps forward by many many ticks.> > -----Original Message-----> From: XuNanxuan [mailto:nanxuan_xu@live.cn]> Sent: Wednesday, December 03, 2008 11:45 PM> To: xen-devel@lists.xensource.com> Subject: [Xen-devel] Question about time measure in Guest Windows> > > Hi:> > I intend to use RDTSC to make some time tests in Xen guest WinXP. However, from Intel Developer''s Manual I noticed that RDTSC will cause VMExit if "RETSC exiting" VM-Execution control field is 1. So I wonder: How to query VM-Execution control field in a programmable way?> > BTW: On Intel Developer''s Manual, it mentioned a method using IA32_VMX_PROCBASED_CTLS MSR, but this is just to report which bits can be set on processor-based VM-EXECUTION controls, rather than telling you the content of this structure.> > Thanks! _________________________________________________________________ 超炫人气榜给您所有偶像的最新资讯和排名,快来支持自己的偶像! http://cnweb.search.live.com/xrank/results.aspx?q=%e5%91%a8%e6%9d%b0%e4%bc%a6&FORM=MSNH _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel