linux/arch/s390/kvm/Kconfig
Christian Borntraeger 0eaeafa10f [S390] s390-kvm: leave sie context on work. Removes preemption requirement
From: Martin Schwidefsky <schwidefsky@de.ibm.com>

This patch fixes a bug with cpu bound guest on kvm-s390. Sometimes it
was impossible to deliver a signal to a spinning guest. We used
preemption as a circumvention. The preemption notifiers called
vcpu_load, which checked for pending signals and triggered a host
intercept. But even with preemption, a sigkill was not delivered
immediately.

This patch changes the low level host interrupt handler to check for the
SIE  instruction, if TIF_WORK is set. In that case we change the
instruction pointer of the return PSW to rerun the vcpu_run loop. The kvm
code sees an intercept reason 0 if that happens. This patch adds accounting
for these types of intercept as well.

The advantages:
- works with and without preemption
- signals are delivered immediately
- much better host latencies without preemption

Acked-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2008-05-07 09:23:01 +02:00

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#
# KVM configuration
#
config HAVE_KVM
bool
menuconfig VIRTUALIZATION
bool "Virtualization"
default y
---help---
Say Y here to get to see options for using your Linux host to run other
operating systems inside virtual machines (guests).
This option alone does not add any kernel code.
If you say N, all options in this submenu will be skipped and disabled.
if VIRTUALIZATION
config KVM
tristate "Kernel-based Virtual Machine (KVM) support"
depends on HAVE_KVM && EXPERIMENTAL
select PREEMPT_NOTIFIERS
select ANON_INODES
select S390_SWITCH_AMODE
---help---
Support hosting paravirtualized guest machines using the SIE
virtualization capability on the mainframe. This should work
on any 64bit machine.
This module provides access to the hardware capabilities through
a character device node named /dev/kvm.
To compile this as a module, choose M here: the module
will be called kvm.
If unsure, say N.
config KVM_TRACE
bool
# OK, it's a little counter-intuitive to do this, but it puts it neatly under
# the virtualization menu.
source drivers/virtio/Kconfig
endif # VIRTUALIZATION