Re: [PATCH] arm64: dts: uniphier: add /memreserve/ for spin-table release address

From: Mark Rutland
Date: Mon Apr 18 2016 - 05:04:43 EST

On Mon, Apr 18, 2016 at 05:55:14PM +0900, Masahiro Yamada wrote:
> 2016-04-18 17:45 GMT+09:00 Mark Rutland <mark.rutland@xxxxxxx>:
> > I take it that the code for the spin-table is not in RAM, and does not
> > need to be protected similarly?
> I use U-Boot to boot Linux for this board.
> The code for the spin-table is on SDRAM, and not protected.
> I already recognize this problem.
> The difficulty for U-Boot is that
> U-Boot relocates itself to the top of the DRAM.
> So, it is difficult to predict
> where the code will be placed.
> I will discuss this issue in the U-Boot ML.

Ok, please do.

> So, My current solution is pre-fetch the code for the spin-table onto
> I-cache.

As you are probably aware, this is incredibly unsafe, and very likely to
go wrong. Nothing guarantees that (stale) entries remain in the I-cache.

I would very much advise fixing this ASAP.