On Thu, 2010-03-11 at 12:27 +0900, Shinya Kuribayashi wrote: > Wu Zhangjin wrote: > > From: Wu Zhangjin <wuzhangjin@xxxxxxxxx> > > > > As the Chapter 15: "Errata: Issue of Out-of-order in loongson"[1] shows, to > > workaround the Issue of Loongson-2F，We need to do: > > > > "When switching from user model to kernel model, you should flush the branch > > target history such as BTB and RAS." > > Just wondered, model or mode? > Hmm, should be mode. > > This patch did clear BTB(branch target buffer), forbid RAS(row address strobe) > > via Loongson-2F's 64bit diagnostic register. > > Are you sure that RAS represents "Row Address Strobe", not "Return > Address Stack?" > Hi, Yanhua(from Lemote), can you help to clear this part? > By the way, we have a similar local workaround for vr55xx processors > when switching from kernel mode to user mode. It's not necessarily > related to out-of-order issues, but we need to prevent the processor > from doing instruction prefetch beyond "eret" instruction. > > In the long term, it would be appreciated that the kernel has a set > of hooks when switching KUX-modes, so that each machine could have > his own, processor-specific treatmens. > Good idea. Thanks! Regards, Wu Zhangjin
