Re: [PATCH 0/8] Fix 8xx MMU/TLB

On Tue, Oct 27, 2009 at 10:16:17AM +0100, Joakim Tjernlund wrote:

Benjamin Herrenschmidt [off-list ref] wrote on 27/10/2009 01:00:53:

quoted

On Mon, 2009-10-26 at 16:26 -0700, Dan Malek wrote:

quoted

Just be careful the get_user() doesn't regenerate the same
translation error you are trying to fix by being here......

yes, I had some problems with this initially but managed to work around
that. I noticed another problem though, I got multiple TLB errors for the
same address when I did it in C. Noticed by just printk:ing every hit for
a dcbX insn in do_page_fault. I can't explain it, but it seems like when
moving to C you have to execute a rfi insn and that might somehow restart
the dcbX insn before moving on to the page fault routine(or something
totally different)

The rfi should be to other kernel code -- there is no way that it should be
restarting the dcbX (other than when trying to turn a TLB miss into a TLB
error).  Can you post the C version, maybe we can see what's going wrong? 
Is the empty TLB entry from the miss getting invalidated in the dcbX fixup
case?

quoted

It shouldn't since it will always come up with a proper DAR but
you may want to double check before hand that your instruction
address you are loading from is -not- your marker value for bad DAR.

hmm, I check that the insn really is a dcbX insn, but not that the address is
!= 0x00f0. Don't see how it could be as if something is wrong with
the insn address you get ITLB error instead of a DTLB error.

I'm guessing he meant the data address you're loading.

Anyhow, things seems stalled as I haven't heard from Scott or Rex for a
while. If this isn't working now, I really don't know what is wrong and
need some debugging help.

I'll test the latest version, but I have some scheduling latency. :-)

-Scott