Re: MSI/MSI-X implementation and interrupt handling on i386/amd64

[Jaromír Doleček <jaromir.dolecek%gmail.com@localhost>]

Moving this to port-amd64 (bcced current-users@ for reference)

Le mar. 11 déc. 2018 à 04:34, Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost> a écrit :
> I mention some old Athlon 64 series (before socket AM2) do not support
> cmpxchg16b instruction. That would affect rewriting spllower to support
> 64 bit interrupt bitmask.

Indeed, need to do runtime check for cmpxchg16b support.

I'm investigating an initial solution which will keep the
ipending+ilevel still as 64-bit quantity suitable for cmpxchg8b, using
4 bits for the ilevel and remaining 60 for ipending.

The 60/4 split with cmpxchg8b should work for i386 too. Besides
spl.S/vector.S, so far I only found one place using atomic write on
the ipending - clearing interrupt from ipending in intr disestablish.
This one can easily change to just block all interrupts during the
clearing, since this is not performance critical path.

Jaromir