Re: rng padlock changes causes NetBSD to crash

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Thu, Feb 16, 2017 at 01:04:33PM +0200, Andrius V wrote:
> Hi,
> 
> I have tested the fix.  lcr4(rcr4() | CR4_OSFXSR); helps indeed and
> system boots but if statement seems to be not correct, at least on
> VT-310DP board it ended up in the same error.

I checked in an unconditional version of the fix.

It's interesting to note (again as pointed out by jak@) 64 bit
kernels would not have had this problem, since they enable SSE
very early in CPU startup.

The underlying hardware cause for this seems to also be why we
must mess with the coprocessor enables in CR0 before calling
any ACE/RNG instructions -- in Jonathan's testing, even a single
call to xstorerng causes a coprocessor (DNA) fault if the FPU's
off.  Unfortunate, since all that monkeying around (interrupt
disable, turn off preemption, whack coproc regs) increases the
cost of getting 8 random bytes by a factor of at least 10.

The VIA manual suggests they intended to move PadLock out of
the FPU in later designs but I think at this point it is
fairly clear there won't be any of those.

Thor