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Re: Rep:Re: [f-cpu] virtually or physically-addressed cache ?

----- Original Message -----
From: Marco Al <marco@simplex.nl>
To: <f-cpu@seul.org>
Sent: Sunday, March 03, 2002 5:54 PM
Subject: Re: Rep:Re: [f-cpu] virtually or physically-addressed cache ?

> From: "Christophe" <christophe.avoinne@laposte.net>
> > Why might there be severe problems ? well, caches both contains a tag and
> > a data associated to a virtual address. If there are two
> > different virtual addresses which span the same physical address and are
> > present in the cache, it means that two entries in the
> > cache might also have their data to be different and so coherency would be
> > broken : which data to keep and update into the external
> > memory ?
> There is a simple software solution to this, dont allow the OS to let that
> happen :) With 64 bit's to go around you dont really need per process memory
> spaces (you still need per process memory protection of course, but you dont
> need to go to external memory to change that).

Lazy solution for my opinion. Not viable for micro kernel or exo kernel which really counts upon sharing
some physical pages in different virtual addresses with different access rights.

Anyway, if an OS programmer wants to use per process address spaces, he should be able to do so. Having it
doesn't prevent us from being able to use a unique address space if we like.

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