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    SubjectRe: linux-next: Tree for January 23 (kvm)
    (cc mailing lists)

    On Wed, 28 Jan 2009 12:26:16 -0200
    Marcelo Tosatti <mtosatti@redhat.com> wrote:

    > On Wed, Jan 28, 2009 at 11:20:16AM +0100, Alexander Graf wrote:
    > >
    > > On 28.01.2009, at 10:51, Andrew Morton wrote:
    > >
    > >> On Fri, 23 Jan 2009 12:34:24 -0800 Randy Dunlap
    > >> <randy.dunlap@oracle.com> wrote:
    > >>
    > >>> Stephen Rothwell wrote:
    > >>>> Hi all,
    > >>>>
    > >>>> News: I will be on leave next week, so there will probably be no
    > >>>> linux-next release until Feb 2.
    > >>>>
    > >>>> Changes since 20090122:
    > >>>
    > >>>
    > >>> kvm changes cause this build error on i386:
    > >>>
    > >>> when kvm is built as module:
    > >>> ERROR: "__moddi3" [arch/x86/kvm/kvm.ko] undefined!
    > >>>
    > >>> or when kvm is built into the kernel image:
    > >>> lapic.c:(.text+0x19276): undefined reference to `__moddi3'
    > >>>
    > >>>
    > >>> I guess it's this line:
    > >>> ns = ktime_to_ns(remaining) % apic->timer.period;
    > >>>
    > >>
    > >> dammit, I just spent N minutes hunting down the same thing in
    > >> the Jan 26 linux-next :(
    > >>
    > >
    > > Yeah, Clemens Foss posted a real fix on kvm@vger already.

    Probably wasn't the best mailing list, as this bug affects all
    developers and testers.. But whatever - thanks.

    > commit efe4ff38b2bbc3944d0b2c9b6ec669b67cb7acbc
    > Author: Clemens Noss <cnoss@gmx.de>
    > Date: Mon Jan 26 02:55:16 2009 +0100
    >
    > KVM: x86: fix "__moddi3 undefined" build failure in lapic.c
    >
    > use mod_64 from arch/x86/kvm/i8254.c to fix
    > ERROR: "__moddi3" [arch/x86/kvm/kvm.ko] undefined!
    >
    > Signed-off-by: Clemens Noss <cnoss@gmx.de>
    > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
    >
    > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
    > index d8adc50..f0b67f2 100644
    > --- a/arch/x86/kvm/lapic.c
    > +++ b/arch/x86/kvm/lapic.c
    > @@ -35,6 +35,12 @@
    > #include "kvm_cache_regs.h"
    > #include "irq.h"
    >
    > +#ifndef CONFIG_X86_64
    > +#define mod_64(x, y) ((x) - (y) * div64_u64(x, y))
    > +#else
    > +#define mod_64(x, y) ((x) % (y))
    > +#endif
    > +
    > #define PRId64 "d"
    > #define PRIx64 "llx"
    > #define PRIu64 "u"
    > @@ -525,7 +531,7 @@ static u32 apic_get_tmcct(struct kvm_lapic *apic)
    > if (ktime_to_ns(remaining) < 0)
    > remaining = ktime_set(0, 0);
    >
    > - ns = ktime_to_ns(remaining) % apic->timer.period;
    > + ns = mod_64(ktime_to_ns(remaining), apic->timer.period);
    > tmcct = div64_u64(ns, (APIC_BUS_CYCLE_NS * apic->timer.divide_count));
    >
    > return tmcct;

    Rather than cooking up a private implementation I think it would be
    better to implement a kernel-wide mod64_u64() (?) facility and then to
    use that in KVM. There will presumably be other sites which will (or
    already do) need such a thing.

    However it'll probably be a bit hard, getting the signednesses of the
    args and the return value right.



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