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    SubjectRe: [patch 4/5] x2apic, IR: remove reinit_intr_remapped_IO_APIC()

    * Han, Weidong <weidong.han@intel.com> wrote:

    > Siddha, Suresh B wrote:
    > > On Tue, 2009-04-21 at 00:01 -0700, Ingo Molnar wrote:
    > >> * Han, Weidong <weidong.han@intel.com> wrote:
    > >>
    > >>> Siddha, Suresh B wrote:
    > >>>> When interrupt-remapping is enabled, We are relying on
    > >>>> setup_IO_APIC_irqs() to configure remapped entries in the IO-APIC,
    > >>>> which comes little bit later after enabling interrupt-remapping.
    > >>>>
    > >>>> Meanwhile, Restore of old io-apic entries after enabling
    > >>>> interrupt-remapping will not make the interrupts through io-apic
    > >>>> functional anyway.
    > >>>>
    > >>>> So remove unnecessary reinit_intr_remapped_IO_APIC().
    > >>>>
    > >>>> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
    > >>>> Cc: Weidong Han <weidong.han@intel.com>
    > >>>> ---
    > >>>>
    > >>>> Index: tip/arch/x86/include/asm/io_apic.h
    > >>>> ===================================================================
    > >>>> --- tip.orig/arch/x86/include/asm/io_apic.h
    > >>>> +++ tip/arch/x86/include/asm/io_apic.h
    > >>>> @@ -166,8 +166,6 @@ extern void free_ioapic_entries(struct I
    > >>>> extern int save_IO_APIC_setup(struct IO_APIC_route_entry
    > >>>> **ioapic_entries); extern void mask_IO_APIC_setup(struct
    > >>>> IO_APIC_route_entry **ioapic_entries); extern int
    > >>>> restore_IO_APIC_setup(struct IO_APIC_route_entry **ioapic_entries);
    > >>>> -extern void reinit_intr_remapped_IO_APIC(int intr_remapping,
    > >>>> - struct IO_APIC_route_entry **ioapic_entries);
    > >>>>
    > >>>> extern void probe_nr_irqs_gsi(void);
    > >>>>
    > >>>> Index: tip/arch/x86/kernel/apic/apic.c
    > >>>> ===================================================================
    > >>>> --- tip.orig/arch/x86/kernel/apic/apic.c
    > >>>> +++ tip/arch/x86/kernel/apic/apic.c
    > >>>> @@ -1416,8 +1416,6 @@ end_restore:
    > >>>> * IR enabling failed
    > >>>> */
    > >>>> restore_IO_APIC_setup(ioapic_entries);
    > >>>> - else
    > >>>> - reinit_intr_remapped_IO_APIC(x2apic_preenabled, ioapic_entries);
    > >>>
    > >>> Whether IR enabling succeeds or fails, it always needs to restore
    > >>> old IOAPIC entries. Due to removing reinit_intr_remapped_IO_APIC
    > >>> here, it needs to also remove the "if (ret)" before
    > >>> restore_IO_APIC_setup(ioapic_entries);
    > >>
    > >> Ok - i skipped this patch for now.
    > >
    > > Let me clarify what I am doing in this patch:
    > >
    > > When interrupt-remapping is enabled, IO-APIC entries need to be setup
    > > in the re-mappable format (pointing to interrupt-remapping table
    > > entries setup by the OS). This remapping configuration is happening
    > > in the same place where we traditionally configure IO-APIC (i.e., in
    > > setup_IO_APIC_irqs()).
    > >
    > > So when we enable interrupt-remapping successfully, there is no need
    > > to restore old io-apic RTE entries before we actually do a complete
    > > configuration shortly in setup_IO_APIC_irqs(). Old IO-APIC RTE's may
    > > be in traditional format (non re-mappable) or in re-mappable format
    > > pointing to interrupt-remapping table entries setup by BIOS. Restoring
    > > both of these will not make IO-APIC functional. We have to rely on
    > > setup_IO_APIC_irqs() for proper configuration by OS.
    > >
    > > So I am removing this unnecessary and broken step.
    > >
    > > When enabling interrupt-remapping is not successful, we are doing
    > > plain restore of old RTE's (which will still work as we went back to
    > > original no-remapping state). Complete IO-APIC configuration will be
    > > done shortly in setup_IO_APIC_irqs().
    > >
    >
    > Clear explanation. I misunderstood it. This patch is fine.

    Applied to tip:x86/apic - thanks guys,

    Ingo


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