Re: [PATCH-2] NMI trap revised (was Re: NMI errors in 2.0.30??) (fwd)
Systemkennung Linux (linux@mailhost.uni-koblenz.de)
Thu, 15 May 1997 04:46:47 +0200 (MET DST)
>
> On Tue, 13 May 1997, Gabriel Paubert wrote:
>
> > During the NMI routine all interrupts are masked anyway, and even NMIs are
> > masked until the CPU executes an IRET instruction. But the problem is
> > printk...
>
> Not true with ix86 processors. To mask non-maskable interrupts you adjust
> a bit in port 0x61 (I don't have the documentation here). This is the
> "keyboard" chip which is really a port/uP with built-in ROM. This
> physically disconnects the NMI line to the processor. I think it is
> either bit 4 or 5. Anyway non-maskable interrupts are not maskable which
> means CLI and STI don't affect them. Therefore the INT bit in the flags
> register (which would be restored from the stack upon an IRET) does not
> affect it.
Dick ist right. Hey, after all NMI stands for "Non Maskable Interrupt" ...
Ralf