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18863bdd60
The various syscall-related MSRs are fairly expensive to switch. Currently we switch them on every vcpu preemption, which is far too often: - if we're switching to a kernel thread (idle task, threaded interrupt, kernel-mode virtio server (vhost-net), for example) and back, then there's no need to switch those MSRs since kernel threasd won't be exiting to userspace. - if we're switching to another guest running an identical OS, most likely those MSRs will have the same value, so there's little point in reloading them. - if we're running the same OS on the guest and host, the MSRs will have identical values and reloading is unnecessary. This patch uses the new user return notifiers to implement last-minute switching, and checks the msr values to avoid unnecessary reloading. Signed-off-by: Avi Kivity <avi@redhat.com>
71 lines
1.9 KiB
Text
71 lines
1.9 KiB
Text
#
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# KVM configuration
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#
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source "virt/kvm/Kconfig"
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menuconfig VIRTUALIZATION
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bool "Virtualization"
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depends on HAVE_KVM || X86
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default y
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---help---
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Say Y here to get to see options for using your Linux host to run other
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operating systems inside virtual machines (guests).
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This option alone does not add any kernel code.
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If you say N, all options in this submenu will be skipped and disabled.
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if VIRTUALIZATION
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config KVM
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tristate "Kernel-based Virtual Machine (KVM) support"
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depends on HAVE_KVM
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# for device assignment:
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depends on PCI
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select PREEMPT_NOTIFIERS
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select MMU_NOTIFIER
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select ANON_INODES
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select HAVE_KVM_IRQCHIP
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select HAVE_KVM_EVENTFD
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select KVM_APIC_ARCHITECTURE
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select USER_RETURN_NOTIFIER
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---help---
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Support hosting fully virtualized guest machines using hardware
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virtualization extensions. You will need a fairly recent
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processor equipped with virtualization extensions. You will also
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need to select one or more of the processor modules below.
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This module provides access to the hardware capabilities through
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a character device node named /dev/kvm.
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To compile this as a module, choose M here: the module
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will be called kvm.
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If unsure, say N.
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config KVM_INTEL
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tristate "KVM for Intel processors support"
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depends on KVM
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---help---
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Provides support for KVM on Intel processors equipped with the VT
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extensions.
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To compile this as a module, choose M here: the module
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will be called kvm-intel.
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config KVM_AMD
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tristate "KVM for AMD processors support"
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depends on KVM
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---help---
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Provides support for KVM on AMD processors equipped with the AMD-V
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(SVM) extensions.
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To compile this as a module, choose M here: the module
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will be called kvm-amd.
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# OK, it's a little counter-intuitive to do this, but it puts it neatly under
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# the virtualization menu.
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source drivers/lguest/Kconfig
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source drivers/virtio/Kconfig
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endif # VIRTUALIZATION
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