Hi All, I am trying to provide services to guest VMs where I wish to run guest VMs in a loop. I wish to use a core to schedule a guest VM, service it eg. execute an ISR etc and then return to the context of Xen on that core, so that I can then schedule the next VM on that core. In doing all this, the goal is to avoid the calls to VMEntry and VMExit. Is there a workaround for this to be done or will I always have to face a VMExit to return to the Xen context on that core ? Looking forward to some pointers. Thanks, Devdutt. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Is this for HVM? AFAIK you can''t really avoid doing a VMexit from HVM guest mode if you want to get back to Xen: Xen just doesn''t exist in the address space of the guest. For PV guests, Xen is mapped into the address space so you basically just need to do a ring transition. Cheers, Mark> I am trying to provide services to guest VMs where I wish to run guest VMs > in a loop. > > I wish to use a core to schedule a guest VM, service it eg. execute an ISR > etc and then return to the context of Xen on that core, so that I can then > schedule the next VM on that core. > In doing all this, the goal is to avoid the calls to VMEntry and VMExit. Is > there a workaround for this to be done or will I always have to face a > VMExit to return to the Xen context on that core ? > > Looking forward to some pointers. > > Thanks, > Devdutt.-- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Yes, this is for HVM. On a related note, is there any bit in the VMCS region that will cause an IRET in the guest VM to trap into Xen so that I can then service another VM ? On Oct 29, 2007 7:42 PM, Mark Williamson <mark.williamson@cl.cam.ac.uk> wrote:> Is this for HVM? AFAIK you can''t really avoid doing a VMexit from HVM guest > mode if you want to get back to Xen: Xen just doesn''t exist in the address > space of the guest. > > For PV guests, Xen is mapped into the address space so you basically just need > to do a ring transition. > > Cheers, > Mark > > > > I am trying to provide services to guest VMs where I wish to run guest VMs > > in a loop. > > > > I wish to use a core to schedule a guest VM, service it eg. execute an ISR > > etc and then return to the context of Xen on that core, so that I can then > > schedule the next VM on that core. > > In doing all this, the goal is to avoid the calls to VMEntry and VMExit. Is > > there a workaround for this to be done or will I always have to face a > > VMExit to return to the Xen context on that core ? > > > > Looking forward to some pointers. > > > > Thanks, > > Devdutt. > > > > -- > Dave: Just a question. What use is a unicyle with no seat? And no pedals! > Mark: To answer a question with a question: What use is a skateboard? > Dave: Skateboards have wheels. > Mark: My wheel has a wheel! >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
There is no such a bit in VMCS that indicates HVM guest''s IRET should incur VMexit, though the "External-interrupt exiting" and "NMI exiting" may cause VMexit on HVM guest''s IRET under certain conditions. -- Dexuan Devdutt Patnaik wrote:> Yes, this is for HVM. On a related note, is there any bit in the VMCS > region that will cause an IRET in the guest VM to trap into Xen so > that I can then service another VM ? >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Cui, Dexuan wrote:> There is no such a bit in VMCS that indicates HVM guest''s IRET should > incur VMexit, though the "External-interrupt exiting" and "NMI > exiting" may cause VMexit on HVM guest''s IRET under certain > conditions.Sorry, they should be "Interrupt-window exiting" and "NMI-window exiting". -- Dexuan> Devdutt Patnaik wrote: >> Yes, this is for HVM. On a related note, is there any bit in the VMCS >> region that will cause an IRET in the guest VM to trap into Xen so >> that I can then service another VM ?_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel