Re: [Xen-ia64-devel] [PATCH] tlb miss handler

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Jeudi 26 Janvier 2006 13:59, Isaku Yamahata a écrit :
> This patch is not for commit.  But for review, commnets.
>
> Current itlb/dtlb miss handlers don't handle a tlb miss
> in xen/ia64 identity mapping area.
> Such a miss might occur because xen/ia64 enables vhpt walker
> even for region 7. (Please see set_one_rr())
> I haven't encountered it yet, I'm guessing so from reading code.
>
> Vti itlb/dtlb miss handlers do it by checking psr.vm bits.
> This patch is not so optimized for review,
> but it should be done later.
Quiet interesting because I have just worked a little bit in this area.

My comments:
itlb miss must not occur, since Xen is mapped with a itm.
dtlb miss should not occur for the same reason, but they occur at least during 
start-up while Xen reads bootparams and EFI.  This is done before enabling 
VHPT.

So i/d tlb miss in Xen should crash (and invoke debugger you have added).

BTW, I think the size of the identity mapped region should be shrinked in 
order to enabled virtual memory in Xen.  This will be necessary for virtual 
mem map.  That's the point I have looked.

Things are easy now, but could change due to NUMA or sparse memory!

Tristan.


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