Re: [tip:x86/urgent] x86, apic: Don't use logical-flat mode when CPU hotplug may exceed 8 CPUs

[Yinghai Lu <yinghai@kernel.org>]

On 02/09/2010 06:26 PM, Yinghai Lu wrote:
> On 02/09/2010 06:01 PM, Suresh Siddha wrote:
>> On Tue, 2010-02-09 at 10:47 -0800, Yinghai Lu wrote:
>>>>  #ifdef CONFIG_X86_32
>>>> -	if (num_processors > 8) {
>>>> +	if (num_possible_cpus() > 8) {
>>>
>>> for 32bit you can not use this function yet.
>>> that only can be used after prefill_possible_map()
>>
>> Yinghai, Agreed. How about the appended patch? I tested and it works.
>> Peter wants a small quick fix for this issue (to resolve the boot issue
>> reported in the virtualization guest context) so that we can queue it
>> for .33 and .32 kernels (as some distributions will be based on these
>> kernels).
>>
>> Can you please Ack if it is ok?
>>
>> thanks,
>> suresh
>> ---
>>
>> From: Suresh Siddha <suresh.b.siddha@intel.com>
>> Subject: x86, apic: Don't use logical-flat mode when CPU hotplug may exceed 8 CPUs
>>
>> We need to fall back from logical-flat APIC mode to physical-flat mode
>> when we have more than 8 CPUs.  However, in the presence of CPU
>> hotplug(with bios listing not enabled but possible cpus as disabled cpus in
>> MADT), we have to consider the number of possible CPUs rather than
>> the number of current CPUs; otherwise we may cross the 8-CPU boundary
>> when CPUs are added later.
>>
>> 32bit apic code can use more cleanups (like the removal of vendor checks in
>> 32bit default_setup_apic_routing()) and more unifications with 64bit code.
>> Yinghai has some patches in works already. This patch addresses the boot issue
>> that is reported in the virtualization guest context.
>>
>> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
>> Acked-by: Shaohui Zheng <shaohui.zheng@intel.com>
>> Cc: <stable@kernel.org>
>> ---
>>
>> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
>> index 036d28a..0acbcdf 100644
>> --- a/arch/x86/kernel/acpi/boot.c
>> +++ b/arch/x86/kernel/acpi/boot.c
>> @@ -1185,9 +1185,6 @@ static void __init acpi_process_madt(void)
>>  		if (!error) {
>>  			acpi_lapic = 1;
>>  
>> -#ifdef CONFIG_X86_BIGSMP
>> -			generic_bigsmp_probe();
>> -#endif
>>  			/*
>>  			 * Parse MADT IO-APIC entries
>>  			 */
>> @@ -1197,8 +1194,6 @@ static void __init acpi_process_madt(void)
>>  				acpi_ioapic = 1;
>>  
>>  				smp_found_config = 1;
>> -				if (apic->setup_apic_routing)
>> -					apic->setup_apic_routing();
>>  			}
>>  		}
>>  		if (error == -EINVAL) {
>> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
>> index a85f216..6e29b2a 100644
>> --- a/arch/x86/kernel/apic/apic.c
>> +++ b/arch/x86/kernel/apic/apic.c
>> @@ -1641,9 +1641,7 @@ int __init APIC_init_uniprocessor(void)
>>  #endif
>>  
>>  	enable_IR_x2apic();
>> -#ifdef CONFIG_X86_64
>>  	default_setup_apic_routing();
>> -#endif
>>  
>>  	verify_local_APIC();
>>  	connect_bsp_APIC();
>> @@ -1891,21 +1889,6 @@ void __cpuinit generic_processor_info(int apicid, int version)
>>  	if (apicid > max_physical_apicid)
>>  		max_physical_apicid = apicid;
>>  
>> -#ifdef CONFIG_X86_32
>> -	if (num_processors > 8) {
>> -		switch (boot_cpu_data.x86_vendor) {
>> -		case X86_VENDOR_INTEL:
>> -			if (!APIC_XAPIC(version)) {
>> -				def_to_bigsmp = 0;
>> -				break;
>> -			}
>> -			/* If P4 and above fall through */
>> -		case X86_VENDOR_AMD:
>> -			def_to_bigsmp = 1;
>> -		}
>> -	}
>> -#endif
>> -
>>  #if defined(CONFIG_SMP) || defined(CONFIG_X86_64)
>>  	early_per_cpu(x86_cpu_to_apicid, cpu) = apicid;
>>  	early_per_cpu(x86_bios_cpu_apicid, cpu) = apicid;
>> diff --git a/arch/x86/kernel/apic/probe_32.c b/arch/x86/kernel/apic/probe_32.c
>> index 1a6559f..88e78ae 100644
>> --- a/arch/x86/kernel/apic/probe_32.c
>> +++ b/arch/x86/kernel/apic/probe_32.c
>> @@ -54,6 +54,31 @@ late_initcall(print_ipi_mode);
>>  
>>  void default_setup_apic_routing(void)
>>  {
>> +	int version = apic_version[boot_cpu_physical_apicid];
>> +
>> +	if (num_possible_cpus() > 8) {
>> +		switch (boot_cpu_data.x86_vendor) {
>> +		case X86_VENDOR_INTEL:
>> +			if (!APIC_XAPIC(version)) {
>> +				def_to_bigsmp = 0;
>> +				break;
>> +			}
>> +			/* If P4 and above fall through */
>> +		case X86_VENDOR_AMD:
>> +			def_to_bigsmp = 1;
>> +		}
>> +	}
>> +
>> +#ifdef CONFIG_X86_BIGSMP
>> +	generic_bigsmp_probe();
>> +#endif
>> +
>> +	if (apic->setup_apic_routing)
>> +		apic->setup_apic_routing();
> 
> the main difference between this patch and
> http://patchwork.kernel.org/patch/74525/
> 
> is moving apic->setup_apic_routing calling.
> 
> wonder if it will affect subarch other than logical flat and physical flat.

other subarch setup_apic_routing is just pr_info...

so your patch should be ok.

YH