Re: [f-cpu] TLB resume

[nico <nicolas.boulay@ifrance.com>]

cedric a écrit :
> 
> Here is an extract from the TLB discussion that append one month ago.
> 
> Michael propose this :
> "
> I've been thinking about the TLB before; IMHO, we need at least the
> following (assuming <n> bits for the page offset):
> 
>         - virtual address (64-<n> bits)
>         - physical address (64-<n> bits)
>         - address space identifier (ASI; 8 bits was suggested)
>         - supervisor access rights (RWX, 3 bits)
>         - user access rights (RWX, 3 bits)
>         - valid bit (indicating that the entry is valid)
>         - dirty bit (indicating that the page has been written to)
>         - used bit (indicating that the page has been accessed)
> 
>         - page size (4K << size, 6 bits)

-> too much ?

> "
> 
> "present bits" has been removed because it's only needed by HW TLB after the
> discussion. I hope I have maid a good resume, but if someone want to add
> something, before I add this to the manual (perhaps we must clarify how to
> access it before).
> 
> Cedric

So to resume one more time every one is ok with that.Christophe think
it's better to use supervisor right, so why not ! (just one question :
we want to avoid that user could give kernel adresse to OS call, so we
want to put no-read bit on kernel data page, so how the kernel could
read it's own pages ?)

For the page size, 4k << size is a little bit too much. I prefer
something like previously said:
- tiny for message passing ~4Ko
- usual page for program 64~256 Kb
- For kernel, frame buffer 4-64 Mb
- udge for data base,... 256-1024 Mb

I propose to not fixed the size now but let it to be defined "later".

Could Cédric put that in the manual ?

nicO
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