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Avi Kivity authored
On x86_64, we can defer %ds and %es reload to the heavyweight context switch, since nothing in the lightweight paths uses the host %ds or %es (they are ignored by the processor). Furthermore we can avoid the load if the segments are null, by letting the hardware load the null segments for us. This is the expected case. On i386, we could avoid the reload entirely, since the entry.S paths take care of reload, except for the SYSEXIT path which leaves %ds and %es set to __USER_DS. So we set them to the same values as well. Saves about 70 cycles out of 1600 (around 4%; noisy measurements). Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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