KVM: VMX: Avoid saving and restoring msr_efer on lightweight vmexit

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MSR_EFER.LME/LMA bits are automatically save/restored by VMX
hardware, KVM only needs to save NX/SCE bits at time of heavy
weight VM Exit. But clearing NX bits in host envirnment may
cause system hang if the host page table is using EXB bits,
thus we leave NX bits as it is. If Host NX=1 and guest NX=0, we
can do guest page table EXB bits check before inserting a shadow
pte (though no guest is expecting to see this kind of gp fault).
If host NX=0, we present guest no Execute-Disable feature to guest,
thus no host NX=0, guest NX=1 combination.

This patch reduces raw vmexit time by ~27%.

Me: fix compile warnings on i386.

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

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This commit is contained in:

Eddie Dong 2007-05-21 07:28:09 +03:00 • committed by Avi Kivity

parent f2be4dd654

commit 2cc51560ae

3 changed files with 71 additions and 21 deletions

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2

drivers/kvm/kvm.h

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23

drivers/kvm/kvm_main.c

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67

drivers/kvm/vmx.c

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