Andrew, Tamas thank you very much. I will improve the patch. December 17, 2019 3:13:42 PM UTC, Andrew Cooper <andrew.coop...@citrix.com> пишет: >On 17/12/2019 15:10, Tamas K Lengyel wrote: >> On Tue, Dec 17, 2019 at 8:08 AM Tamas K Lengyel <ta...@tklengyel.com> >wrote: >>> On Tue, Dec 17, 2019 at 7:48 AM Andrew Cooper ><andrew.coop...@citrix.com> wrote: >>>> On 17/12/2019 14:40, Sergey Kovalev wrote: >>>>> On break point event eight context switches occures. >>>>> >>>>> With fast single step it is possible to shorten path for two >context >>>>> switches >>>>> and gain 35% spead-up. >>>>> >>>>> Was tested on Debian branch of Xen 4.12. See at: >>>>> >https://github.com/skvl/xen/tree/debian/knorrie/4.12/fast-singlestep >>>>> >>>>> Rebased on master: >>>>> https://github.com/skvl/xen/tree/fast-singlestep >>>>> >>>>> Signed-off-by: Sergey Kovalev <va...@list.ru> >>>> 35% looks like a good number, but what is "fast single step"? All >this >>>> appears to be is plumbing for to cause an altp2m switch on single >step. >>> Yes, a better explanation would be much needed here and I'm not 100% >>> sure it correctly implements what I think it tries to. >>> >>> This is my interpretation of what the idea is: when using DRAKVUF >(or >>> another system using altp2m with shadow pages similar to what I >>> describe in >https://xenproject.org/2016/04/13/stealthy-monitoring-with-xen-altp2m), >>> after a breakpoint is hit the system switches to the default >>> unrestricted altp2m view with singlestep enabled. When the >singlestep >>> traps to Xen another vm_event is sent to the monitor agent, which >then >>> normally disables singlestepping and switches the altp2m view back >to >>> the restricted view. This patch looks like its short-circuiting that >>> last part so that it doesn't need to send the vm_event out for the >>> singlestep event and should switch back to the restricted view in >Xen >>> automatically. It's a nice optimization. But what seems to be >missing >>> is the altp2m switch itself. >> Never mind, p2m_altp2m_check does the altp2m switch as well, so this >> patch implements what I described above. Please update the patch >> message to be more descriptive (you can copy my description from >> above). > >Also please read CODING_STYLE in the root of the xen repository. The >important ones you need to fix are spaces in "if ( ... )" statements, >and binary operators on the end of the first line rather than the >beginning of the continuation. > >~Andrew
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