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[Xen-devel] Question regarding VM_EXIT and VGA

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: "Sujata Doshi" <sujatadoshi@xxxxxxxxx>
  • Date: Tue, 5 Dec 2006 10:17:53 -0500
  • Delivery-date: Tue, 05 Dec 2006 07:17:50 -0800
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

I am working on a project using WINDOWS guest on XEN archticture. I
have a couple of questions.

As I understand when a VM exit occurs due to I/O like say a mouse
interrupt -- the XEN hypervisor gets a notification and it forwards
the I/O request to the qemu-dm in Domain-0 via an event channel. Now
during this VM exit , is the guest OS blocked ?

Specifically, what about VGA writes are they blocked too during a VM
exit ? The following link explains that to speed up performance a
shared memory area was built between qemu and the hvm guest .

But I am unable to understand as to whether is this shared memory area
is still accessible by the guest vga when a VM exit has taken place
due to another I/O event like a mouse click?

Would appreciate if you could answer my queries.

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