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SubjectRe: [PATCH 12/14] x86 ioapic: Simplify probe_nr_irqs_gsi.
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Yinghai Lu <yinghai@kernel.org> writes:

> On Mon, Mar 29, 2010 at 4:20 PM, Eric W. Biederman
> <ebiederm@xmission.com> wrote:
>> From: Eric W. Biederman <ebiederm@xmission.com>
>>
>> Use the global gsi_end value now that all ioapics have
>> valid gsi numbers instead of a combination of acpi_probe_gsi
>> and walking all of the ioapics and couting their number of
>> entries by hand if acpi_probe_gsi gave us an answer we did
>> not like.
>>
>> This fixes a small bug in probe_nr_irqs_gsi.  Previously
>> acpi_probe_gsi unnecessarily added 1 to the maximum
>> gsi_end value.  gsi_end is already one past the end of
>> the number of gsi's so the additional increment was
>> superfluous.
>>
>> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
>> ---
>>  arch/x86/include/asm/mpspec.h  |    6 ------
>>  arch/x86/kernel/acpi/boot.c    |   23 -----------------------
>>  arch/x86/kernel/apic/io_apic.c |   17 +++--------------
>>  3 files changed, 3 insertions(+), 43 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
>> index 29994f0..c82868e 100644
>> --- a/arch/x86/include/asm/mpspec.h
>> +++ b/arch/x86/include/asm/mpspec.h
>> @@ -105,12 +105,6 @@ extern void mp_config_acpi_legacy_irqs(void);
>>  struct device;
>>  extern int mp_register_gsi(struct device *dev, u32 gsi, int edge_level,
>>                                 int active_high_low);
>> -extern int acpi_probe_gsi(void);
>> -#else /* !CONFIG_ACPI: */
>> -static inline int acpi_probe_gsi(void)
>> -{
>> -       return 0;
>> -}
>>  #endif /* CONFIG_ACPI */
>>
>>  #define PHYSID_ARRAY_SIZE      BITS_TO_LONGS(MAX_APICS)
>> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
>> index 9c48e99..0e514a1 100644
>> --- a/arch/x86/kernel/acpi/boot.c
>> +++ b/arch/x86/kernel/acpi/boot.c
>> @@ -875,29 +875,6 @@ static int __init acpi_parse_madt_lapic_entries(void)
>>  extern int es7000_plat;
>>  #endif
>>
>> -int __init acpi_probe_gsi(void)
>> -{
>> -       int idx;
>> -       int gsi;
>> -       int max_gsi = 0;
>> -
>> -       if (acpi_disabled)
>> -               return 0;
>> -
>> -       if (!acpi_ioapic)
>> -               return 0;
>> -
>> -       max_gsi = 0;
>> -       for (idx = 0; idx < nr_ioapics; idx++) {
>> -               gsi = mp_gsi_routing[idx].gsi_end;
>> -
>> -               if (gsi > max_gsi)
>> -                       max_gsi = gsi;
>> -       }
>> -
>> -       return max_gsi + 1;
>> -}
>> -
>>  static void assign_to_mp_irq(struct mpc_intsrc *m,
>>                                    struct mpc_intsrc *mp_irq)
>>  {
>> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
>> index 996cf8f..b57b7a3 100644
>> --- a/arch/x86/kernel/apic/io_apic.c
>> +++ b/arch/x86/kernel/apic/io_apic.c
>> @@ -3837,22 +3837,11 @@ int __init io_apic_get_redir_entries (int ioapic)
>>
>>  void __init probe_nr_irqs_gsi(void)
>>  {
>> -       int nr = 0;
>> +       int nr;
>>
>> -       nr = acpi_probe_gsi();
>> -       if (nr > nr_irqs_gsi) {
>> +       nr = gsi_end;
>
> you may need +1 here

As documented in my comment that extra +1 has every appearance of a
bug. Nothing is at gsi_end. gsi_end is already at 1 past the last in
use gsi. Therefore an extra +1 puts us two past the end for no
apparent reason.

Eric
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