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Date: Mon, 29 Mar 2010 21:55:25 -0700
From: Yinghai Lu <yinghai@...nel.org>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
CC: "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Jesse Barnes <jbarnes@...tuousgeek.org>,
linux-kernel@...r.kernel.org, Thomas Renninger <trenn@...e.de>,
Suresh Siddha <suresh.b.siddha@...el.com>, len.brown@...el.com,
Tony Luck <tony.luck@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>, linux-acpi@...r.kernel.org,
Iranna D Ankad <iranna.ankad@...ibm.com>,
Gary Hade <garyhade@...ibm.com>,
Natalie Protasevich <protasnb@...il.com>
Subject: Re: [PATCH 12/14] x86 ioapic: Simplify probe_nr_irqs_gsi.
On 03/29/2010 09:43 PM, Eric W. Biederman wrote:
> Yinghai Lu <yinghai@...nel.org> writes:
>
>> On Mon, Mar 29, 2010 at 4:20 PM, Eric W. Biederman
>> <ebiederm@...ssion.com> wrote:
>>> From: Eric W. Biederman <ebiederm@...ssion.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@...ssion.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
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