RE: [Xen-ia64-devel] [RFC][PATCH] [RESEND] support special guest optimisations in the hypervisor

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

>From: Dietmar Hahn [mailto:dietmar.hahn@xxxxxxxxxxxxxxxxxxx]
>Sent: 2007年7月3日 16:02
>To: Alex Williamson
>Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx; Xu, Anthony
>I had a look at this code (didn't do this before because I have no vti
>machine). Everywhere GOS_WINDOWS() is currently used a opt_feature can be
>used.
>First question: Should we add 2 opt_features, one for both region 4 and region
>5, or one for each.
>Second question: would having arguments to this feature calls make sense?

GOS_WINDOWS is used for HVM, it is not convenient for HVM to use hypercall.
At least, I don’t know where to put this hypercall inside guest OS, we can't 
modify it .
For domU and dom0, it is preferred to use hypercall.

While if there is only xenolinux running on domU and dom0, I think there is no 
need to add this hypercall, Xen and xenlinux are cooperative, so you can add any
linux-specific optimizations.

If you want to run other OSes on domU and dom0, it is preferred to use 
hypercall,
I think letting xen know which OS is running on is enough, thus you can add any 
optimizations for this OS at any time. I prefer the method Alex mentioned that
calls set_os_type hypercall at very beginning of guest OS boot.

Using __HYPERVISOR_opt_feature is Ok for me, 
While if you find new place where you can optimize, you need to modify 
structure 
xen_ia64_opt_feature, and call __HYPERVISOR_opt_feature several times in xeno 
linux.


- Anthony

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