[U-Boot] [PATCH 1/2] x86: Add a 'pause' instruction in __udelay() for QEMU target

[Simon Glass]

On 27 July 2015 at 05:16, Bin Meng <bmeng.cn at gmail.com> wrote:
> From: Miao Yan <yanmiaobest at gmail.com>
>
> 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 at gmail.com>
> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
> ---
>
>  arch/x86/lib/tsc_timer.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Acked-by: Simon Glass <sjg at chromium.org>
Tested-by: Simon Glass <sjg at chromium.org>