On Sun, Mar 21, 2010 at 12:02:41PM +0100, Sebastian Andrzej Siewior wrote:
> Since commit 656be92f aka "Load modules to CKSEG0 if
> CONFIG_BUILD_ELF64=n" module support is broken on 64bit. Since then
> modules arr loaded into 32bit compat adresses which are sign extended
> 64bit addresses. The SiByte war handler was not updated and those
> addresses were not recognized by the TLB hadling.
> This patch fixes this by shifting away the upper bits including the R
> and Fill bits. Now we compare VPN2 of C0_ENTRYHI against the matching
> bits at C0_BADVADDR.
Good detective work but I'll check against the errata documents (which
are non-public, sigh ...) before applying your patch.
The M3 workaround in which you found this bug is currently applied to all
Sibyte SB1 cores while probably only a relativly small number of the cores
in circulation are affected so we should refine the workaround to be only
applied if the System Revision Register indicates a system older than
revision C0. This could get rid of 6 instructions which according to the
usual rule of thumb would result in a speedup of ~ 3%.