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    SubjectRe: [Lguest] lguest: unhandled trap

    * Rusty Russell <rusty@rustcorp.com.au> wrote:

    > On Monday 20 October 2008 18:22:36 Ingo Molnar wrote:
    > > * Rusty Russell <rusty@rustcorp.com.au> wrote:
    > > > On Monday 20 October 2008 12:50:09 Tiago Maluta wrote:
    > > > > --- On Sun, 10/19/08, Rusty Russell <rusty@rustcorp.com.au> wrote:
    > > > > > > Hi,
    > > > > > >
    > > > > > > I'm using 2.6.27-05323-g26e9a39 and when I try to
    > > > > >
    > > > > > use lguest:
    > > > > > > ~#Documentation/lguest/lguest 128 vmlinux
    > > > > > > lguest: unhandled trap 14 at 0xc0594f6a (0xff900000)
    > > > > >
    > > > > > Yes, I found the same issue. Does this fix it for you?
    > > > >
    > > > > Yes. This code fixed the problem.
    > > >
    > > > Thanks. Ingo, can you push this?
    > > >
    > > > Subject: lguest: don't try DMI
    > > >
    > > > dmi_scan_machine breaks under lguest; this is the simplest fix (though
    > > > ugly). Perhaps this hurts Xen too?
    > > >
    > > > Error:
    > > > lguest: unhandled trap 14 at 0xc04edeae (0xffa00000)
    > > >
    > > > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    > > >
    > > > diff -r 47449cd8e3d8 drivers/firmware/dmi_scan.c
    > > > --- a/drivers/firmware/dmi_scan.c Fri Oct 17 12:14:40 2008 +1100
    > > > +++ b/drivers/firmware/dmi_scan.c Fri Oct 17 20:54:30 2008 +1100
    > > > @@ -369,6 +369,11 @@ void __init dmi_scan_machine(void)
    > > > char __iomem *p, *q;
    > > > int rc;
    > > >
    > > > +#ifdef CONFIG_PARAVIRT
    > > > + if (strcmp(pv_info.name, "lguest") == 0)
    > > > + goto error;
    > > > +#endif
    > > > +
    > >
    > > hm, could you give some more background please? I'm not subscribed to
    > > the lguest list and the thread is not Cc:-ed to lkml (Cc:-ed it now).
    > > The patch looks quite ugly because it adds a special-case.
    > >
    > > Was the problem introduced by:
    > >
    > > 5649b7c: x86: add DMI quirk for AMI BIOS which corrupts address 0xc000
    > > during
    > >
    > > perhaps?
    > >
    > > i think Xen can withstand DMI scanning just fine.
    > >
    > > without having seen any background, my general feeling is that lguest
    > > should either do what Xen does and reserve the classic BIOS ranges that
    > > we probe - or we should make DMI scanning more robust by making sure
    > > real RAM ranges are never probed. (only ranges that the BIOS itself
    > > marks as reserved in the e820 map)
    > >
    > > (with exceptions for the first 4K perhaps.)
    > >
    > > Ingo
    >
    > Yes, after this discussion I'm not even sure why it's triggering: even
    > if there's crap in the memory it should not fault. Digging further.

    we could also add an x86_quirks entry to skip the particular DMI scan
    that is causing problems. Would be nice to avoid it though, and fix
    lguest if possible.

    Ingo


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