tree e17f4c3bd50bed2edb0791b6b8fc4faa18658f9c
parent eb47d7c5d96060040931c42773ee07e61e547af9
author Jan Kiszka <jan.kiszka@siemens.com> 1308143846 +0200
committer Avi Kivity <avi@redhat.com> 1308488276 +0300

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 MSR[2]
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 <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>