Upstream KVM opts not to emulate 64-bit FXSAVE / FXRSTOR for good reasons.
However, when we deal with self-inflicted EPT violations, emulating these two instructions can significantly speed up the guest as the emulation avoids the expensive single-stepping and the associated VM-exit & VM-entry.
Effectively, this eliminates two context switches in common situations, e.g., monitoring a task_struct in memory. Initial benchmarks show a speed-up of up to 75%.
Upstream KVM opts not to emulate 64-bit
FXSAVE/FXRSTORfor good reasons. However, when we deal with self-inflicted EPT violations, emulating these two instructions can significantly speed up the guest as the emulation avoids the expensive single-stepping and the associated VM-exit & VM-entry.Effectively, this eliminates two context switches in common situations, e.g., monitoring a
task_structin memory. Initial benchmarks show a speed-up of up to 75%.Best, Thomas