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Date: Thu, 03 Jun 2010 14:07:37 -0400
From: Prarit Bhargava <prarit@...hat.com>
To: Cyrill Gorcunov <gorcunov@...il.com>
CC: linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
mjg@...hat.com, x86@...nel.org,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>, Yinghai Lu <yinghai@...nel.org>,
Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH]: x86: use acpi flags for apic mapping
On 06/03/2010 01:21 PM, Cyrill Gorcunov wrote:
> On Wed, Jun 02, 2010 at 06:20:15PM -0400, Prarit Bhargava wrote:
>
>>
>>>> +#ifdef CONFIG_ACPI
>>>> +enum apic_acpi_map_status apic_is_acpi_clustered_box(void)
>>>> +{
>>>>
>>> It's a bit strange that function is "is" prefixed and returns not true or false
>>> but enum, perhaps we may name it apic_acpi_dst_model() or something like
>>> that?
>>>
>>>
>> Sure, np -- new patch.
>>
>> P.
>>
> Hi Prarit,
>
> just have reviewed it again and got some questions:
>
>
>> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
>> index 1fa03e0..6b63f95 100644
>> --- a/arch/x86/include/asm/apic.h
>> +++ b/arch/x86/include/asm/apic.h
>> @@ -252,6 +252,14 @@ static inline int apic_is_clustered_box(void)
>> }
>> #endif
>>
>> +enum apic_acpi_map_status {
>> + APIC_ACPI_BOTH,
>> + APIC_ACPI_CLUSTER,
>> + APIC_ACPI_PHYSICAL,
>> + APIC_ACPI_NONE
>> +};
>> +extern enum apic_acpi_map_status apic_acpi_dst_model(void);
>> +
>> extern u8 setup_APIC_eilvt_mce(u8 vector, u8 msg_type, u8 mask);
>> extern u8 setup_APIC_eilvt_ibs(u8 vector, u8 msg_type, u8 mask);
>>
>> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
>> index e5a4a1e..e94a189 100644
>> --- a/arch/x86/kernel/apic/apic.c
>> +++ b/arch/x86/kernel/apic/apic.c
>> @@ -2189,6 +2189,30 @@ static const __cpuinitconst struct dmi_system_id multi_dmi_table[] = {
>> {}
>> };
>>
>> +#ifdef CONFIG_ACPI
>> +enum apic_acpi_map_status apic_acpi_dst_model(void)
>> +{
>> + if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) {
>> + if (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL &&
>> + acpi_gbl_FADT.flags & ACPI_FADT_APIC_CLUSTER) {
>> + /*
>> + * The rest of the code assumes physical flat
>> + * in this case.
>> + */
>> + return APIC_ACPI_BOTH;
>> + }
>>
> Havin both flags set in ACPI FADT make me worry -- I suspect this means
> acpi is screwed (this is ok, who doubt :) but the problem is HOW should
> we treat TSC instability in such case? The current code assumes (tsc.c)
>
In the case of BOTH the code will assume physical_flat everywhere --
therefore tsc is is stable. Since the number of cluster systems is low
it is unlikely that BOTH & cluster actually occur. I suppose I could
add (yet another) boot parameter to force cluster/flat/phys_flat if one
doesn't already exist.... but I think that the likelihood of anyone
hitting BOTH & wanting cluster is 0.
> that cluster mode has TSC unstable and if we had both bits set which
> tsc mode we should choose? I suspect we have to assume that TSC unstable
> then.
>
>
>> +
>> + if (acpi_gbl_FADT.flags & ACPI_FADT_APIC_CLUSTER)
>> + return APIC_ACPI_CLUSTER;
>> +
>> + if (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL)
>> + return APIC_ACPI_PHYSICAL;
>> + }
>> +
>> + return APIC_ACPI_NONE;
>> +}
>> +#endif
>> +
>> static void __cpuinit dmi_check_multi(void)
>> {
>> if (multi_checked)
>> @@ -2208,6 +2232,20 @@ static void __cpuinit dmi_check_multi(void)
>> */
>> __cpuinit int apic_is_clustered_box(void)
>> {
>> +#ifdef CONFIG_ACPI
>> + switch (apic_acpi_dst_model()) {
>> + case APIC_ACPI_PHYSICAL:
>> + case APIC_ACPI_BOTH: /* assume physical flat in this case */
>> + return 0;
>> + break;
>> + case APIC_ACPI_CLUSTER:
>> + return 1;
>> + break;
>> + default:
>> + break;
>> + }
>> +#endif
>> +
>> dmi_check_multi();
>> if (multi)
>> return 1;
>> diff --git a/arch/x86/kernel/apic/apic_flat_64.c b/arch/x86/kernel/apic/apic_flat_64.c
>> index 09d3b17..c2318ac 100644
>> --- a/arch/x86/kernel/apic/apic_flat_64.c
>> +++ b/arch/x86/kernel/apic/apic_flat_64.c
>> @@ -231,14 +231,32 @@ static int physflat_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
>> {
>> #ifdef CONFIG_ACPI
>> /*
>> - * Quirk: some x86_64 machines can only use physical APIC mode
>> - * regardless of how many processors are present (x86_64 ES7000
>> - * is an example).
>> + * Some x86_64 machines can only use clustered or physical APIC
>> + * mode regardless of how many processors are present.
>> */
>> - if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
>> - (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL)) {
>> - printk(KERN_DEBUG "system APIC only can use physical flat");
>> - return 1;
>> + switch (apic_acpi_dst_model()) {
>> + case APIC_ACPI_BOTH:
>> + printk(KERN_WARNING FW_BUG "ACPI has set apic mode to "
>> + "both clustered and physical flat. Please "
>> + "contact your firmware vendor for an update.\n");
>> + /*
>> + * In this case assume physical flat as only a very
>> + * limited number of systems use cluster
>> + */
>> + printk(KERN_DEBUG "system APIC using physical flat\n");
>> + return 1;
>> + break;
>> + case APIC_ACPI_CLUSTER:
>> + printk(KERN_DEBUG "system APIC can only use cluster\n");
>> + return 0;
>> + break;
>> + case APIC_ACPI_PHYSICAL:
>> + printk(KERN_DEBUG "system APIC can only use physical"
>> + " flat\n");
>> + return 1;
>> + break;
>> + default:
>> + break;
>> }
>>
> Not sure, but it seems this may broke IBM and EXA machines which should
> use physical destination mode, hmm?
>
Oh -- good point! That's easy to fix though. The acpi check should be
after the IBM & EXA check.
I'll wait for more feedback before reposting ...
P.
>
>>
>> if (!strncmp(oem_id, "IBM", 3) && !strncmp(oem_table_id, "EXA", 3)) {
>>
> Has this patch been tested on real hardware? Asking so since I don't
> have neither IBM nor EXA machine.
>
I have not tested on an IBM or EXA system. However, I have not changed
the existing code -- I'm only adding the ACPI apic mapping which are
currently ignored.
P.
> I'm CC'ing experts I know were involved.
>
> -- Cyrill
>
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