RE: ´ð¸´: [Xen-ia64-devel] Re: [PATCH 0/12] various fixes related the xenrelocation

[tgingold@xxxxxxx]

Quoting "de Dinechin, Christophe (Integrity VM)"
<christophe.de-dinechin@xxxxxx>:

> Another peculiar thing about HPUX, which probably has some impact, is that
> its performance is tuned and dependent on variable page sizes. So you should
> expect for example user-space mappings to contain, say, 4K, 16K, 1M and 4M
> pages for the same process. The reason it may matter for Xen is if you do
> physical address translation (as I assume you do). In that case, it's
> possible that the guest requests 4M of what it thinks is physically
> contiguous memory, but the corresponding host memory is not contiguous. In
> that case, you need to break up the large page into smaller pages.

We do exactly that: break up large pages into smaller pages.  Not really good
for performance...

> Stupid question from a newcomer: what does "metaphysical" mean? Funny name
> ;-)

Indeed.  It is the mode when the guest is in physical (ie MMU disabled) mode.
Invented by Dan, from HP.

> > I think the support is complete enough
> > for VMS although we don't yet support protection keys.  Does HP-UX
> > use them ?
>
> Yes, pretty extensively.

So we will have to add support for them...

> Well, we used to boot with IDE a long time ago, but we have dropped IDE
> support for so long that I cannot really tell if a modern HPUX can still boot
> that way.

Can you boot from CD ?
Which disk controller does HP support and which one does the HP VM emulate ?
(If you are allowed to answer!)

> > Our disk controller and VGA adapter are really basic.
>
> HPUX can boot headless, so no problem even if there is no VGA at all.

Ok.

> > This is definitely not a difficult problem, but may prevent HP-UX
> > from going far.
>
> I don't know enough about how Xen emulates instructions. If there is any
> binary translation of privileged operations (I think that's not the case,
> just checking), then the generated code accesses data in guest endianness,
> and must be ready to deal with (unprivileged) endianness changes.

There are no translation, just emulation.

Tristan.



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