KVM: x86 shared msr infrastructure

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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>

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This commit is contained in:

Avi Kivity 2009-09-07 11:12:18 +03:00

parent 44ea2b1758

commit 18863bdd60

3 changed files with 85 additions and 0 deletions

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3

arch/x86/include/asm/kvm_host.h

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arch/x86/kvm/Kconfig

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81

arch/x86/kvm/x86.c

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