Re: [Xen-devel] [RFC] x86: restore PCI SERR NMI forwarding to Dom0

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 21 Jan 2013, Jan Beulich wrote:
> >>> On 21.01.13 at 16:51, Stefano Stabellini 
> >>> <stefano.stabellini@xxxxxxxxxxxxx>
> wrote:
> > On Thu, 17 Jan 2013, Jan Beulich wrote:
> >> >>> On 17.01.13 at 12:26, Stefano Stabellini 
> >> >>> <stefano.stabellini@xxxxxxxxxxxxx>
> >> wrote:
> >> > On Thu, 17 Jan 2013, Jan Beulich wrote:
> >> >> c/s 22949:54fe1011f86b removed the forwarding of NMIs to Dom0 when they
> >> >> were caused by PCI SERR. NMI buttons as well as BMCs (like HP's iLO)
> >> >> may however want such events to be seen in Dom0 (e.g. to trigger a
> >> >> dump).
> >> >> 
> >> >> I'm therefore suggesting to restore most of the functionality which
> >> >> named c/s removed (adjusted for subsequent changes, and adjusting the
> >> >> public interface to use the modern term, retaining the old one for
> >> >> backwards compatibility).
> >> > 
> >> > Allowing the possibility of injecting these events in Dom0 might be a
> >> > good idea (dom0 just ignores PCI SERR anyway if I recall correctly).
> >> > However the default for opt_nmi in Xen is "fatal", so if I am not
> >> > mistaken you are changing the default Xen behaviour from ignore PCI
> >> > SERR to break down on PCI SERR. I don't think that's a good idea.
> >> 
> >> #ifdef NDEBUG
> >> static char __read_mostly opt_nmi[10] = "dom0";
> >> #else
> >> static char __read_mostly opt_nmi[10] = "fatal";
> >> #endif
> >> 
> >> I.e. debug builds would die, but "normal" builds wouldn't. If the
> >> former is a problem, it's so not only for PCI SERR imo (and would
> >> need fixing here rather than in the patch I sent).
> > 
> > I didn't realize we inverted the DEBUG (NDEBUG now), so I misread the
> > condition.
> > Could we print a more relevant error message then? Not just "MEMORY ERROR",
> > but something about a PCI SERR.
> 
> That's already the case:
> 
> static void pci_serr_softirq(void)
> {
>     printk("\n\nNMI - PCI system error (SERR)\n");
>     outb(inb(0x61) & 0x0b, 0x61); /* re-enable the PCI SERR error line. */
> }
> 
> Oh, you mean in the message before calling fatal_trap() - it's
> an oversight of mine that this still prints MEMORY ERROR. I'll
> get that fix and then submit as non-RFC if that's your only
> concern.

Yes, that's what I meant.

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