Re: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.

From: Avi Kivity
Date: Sun Feb 18 2007 - 06:33:13 EST

Zachary Amsden wrote:
Jeremy Fitzhardinge wrote:
The XEN config option enables the Xen paravirt_ops interface, which is
installed when the kernel finds itself running under Xen. (By some
as-yet fully defined mechanism, implemented in a future patch.)

Xen is no longer a sub-architecture, so the X86_XEN subarch config
option has gone.

The disabled config options are:
- PREEMPT: Xen doesn't support it
- HZ: set to 100Hz for now, to cut down on VCPU context switch rate.
This will be adapted to use tickless later.
- kexec: not yet supported

Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Signed-off-by: Ian Pratt <ian.pratt@xxxxxxxxxxxxx>
Signed-off-by: Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>

We do support different HZ values, although 100HZ is actually preferable for us, so I don't object to that.

Ditto for kvm.

PREEMPT is supported by us, but not as tested as I would like, so I also don't object to dropping it for generic paravirt guests - Rusty - Avi any objections to dropping preempt in terms of lguest/KVM paravirtualization?

I don't have any objections myself, but Ingo (who has done the bulk of the kvm paravirt work; cc'ed) uses PREEMPT_RT, so he will certainly object.

Paravirt-ops definitely needs a hook for kexec, although we should not disable kexec for the natively booted paravirt-ops. Eric - is there a way to disable it at runtime?

kvm paravirt should work correctly with kexec.

We do support the doublefault task gate, and it would be good to keep it, but I can't complain so much if it is gone from generic paravirt kernels for now, because it is non-essential, and generally fatal anyway. We do need it for native boots of paravirt-ops kernels, however, so turning off the config option still needs to be revisited.

kvm doesn't support task gates (a task switch will immediately kill the guest).

error compiling committee.c: too many arguments to function

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