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Revision 42cc8fa6

ID42cc8fa620cbc73e349e96d84cf46469e828ec34

Added by Jan Kiszka almost 13 years ago

kvm: x86: Save/restore FPU OP, IP and DP

These FPU states are properly maintained by KVM but not yet by TCG. So
far we unconditionally set them to 0 in the guest which may cause
state corruptions, though not with modern guests.

To avoid breaking backward migration, use a conditional subsection that
is only written if any of the three fields is non-zero. The guest's
FNINIT clears them frequently, and cleared IA32_MISC_ENABLE MSR2
reduces the probability of non-zero values further so that this
subsection is not expected to restrict migration in any common scenario.

Signed-off-by: Jan Kiszka <>
Signed-off-by: Avi Kivity <>

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