giantlock support

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

Does 8.0 still support giantlocked drivers?  I'm trying to port a
driver from 5.2 to 8.0, and it has a comment saying "This locks against
itself with splhigh().  This essentially depends on either (a) the
machine being uniprocessor or (b) it running giantlocked.  This needs
some love from someone who actually understands NetBSD's MP locking
DKI.".

...but I am not that someone.  I'm wondering if I can get away with
just leaving it non-MPSAFE.  I note that there are still MPSAFE defines
around, but that doesn't necessarily mean leaving them out actually
works.

For that matter, is the comment even correct that splhigh() works for
non-MPSAFE drivers?  It sounds dodgy to me to assume giantlocking works
between interrupt handlers and the main line.  (In case it matters,
it's a PCI/PCIe device, and amd64 is the only port I care about here;
this is, of course, for work.)

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