tree 6888f7074c19e8bee629877c3d359de082a03830
parent 947eb4396dfe11e89f0d3cafe755b395c6c0a8a2
author Miao Yan <yanmiaobest@gmail.com> 1437995767 +0800
committer Simon Glass <sjg@chromium.org> 1438785758 -0600

x86: Add a 'pause' instruction in __udelay() for QEMU target

When running SMP configuration on QEMU (tcg mode, no kvm), there is
a busy loop in start_aps(), calling udelay(), that waits for APs to
show up online. However, there is a chance that VCPU1 will be timeout
waiting, IOW the secondary VCPUs haven't started their execution yet.

This patch adds a 'pause' instruction in __udelay() only for QEMU
target, to give other VCPUs a chance to run. When QEMU sees the
'pause' instruction, it will yeild the execution to other CPUs.

Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>