Re: [PATCH 12/14] x86 ioapic: Simplify probe_nr_irqs_gsi.

[Yinghai Lu <yinghai@kernel.org>]

On 03/29/2010 09:43 PM, Eric W. Biederman wrote:
> 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.

io_apic_get_redir_entries(), and io apic register readingout will return 23 if the total entries is 24.

[    0.000000] ACPI: IOAPIC (id[0x08] address[0xfec00000] gsi_base[0])
[    0.000000] IOAPIC[0]: apic_id 8, version 32, address 0xfec00000, GSI 0-23
[    0.000000] ACPI: IOAPIC (id[0x09] address[0xfec02000] gsi_base[24])
[    0.000000] IOAPIC[1]: apic_id 9, version 32, address 0xfec02000, GSI 24-47
[    0.000000] ACPI: IOAPIC (id[0x0a] address[0xfec04000] gsi_base[48])
[    0.000000] IOAPIC[2]: apic_id 10, version 32, address 0xfec04000, GSI 48-71
[    0.000000] ACPI: IOAPIC (id[0x0b] address[0xfec08000] gsi_base[72])
[    0.000000] IOAPIC[3]: apic_id 11, version 32, address 0xfec08000, GSI 72-95
[    0.000000] ACPI: IOAPIC (id[0x0c] address[0xfec0c000] gsi_base[96])
[    0.000000] IOAPIC[4]: apic_id 12, version 32, address 0xfec0c000, GSI 96-119

        mp_gsi_routing[idx].gsi_end = gsi_base +
            io_apic_get_redir_entries(idx);

        printk(KERN_INFO "IOAPIC[%d]: apic_id %d, version %d, address 0x%x, "
               "GSI %d-%d\n", idx, mp_ioapics[idx].apicid,
               mp_ioapics[idx].apicver, mp_ioapics[idx].apicaddr,
               mp_gsi_routing[idx].gsi_base, mp_gsi_routing[idx].gsi_end);

YH