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

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Message-ID: <4B722B0C.4070604@kernel.org>
Date:	Tue, 09 Feb 2010 19:42:04 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...nel.org" <stable@...nel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Zheng, Shaohui" <shaohui.zheng@...el.com>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/urgent] x86, apic: Don't use logical-flat mode when
 CPU hotplug may exceed 8 CPUs

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@...el.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@...el.com>
> Acked-by: Shaohui Zheng <shaohui.zheng@...el.com>
> Cc: <stable@...nel.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)

__init

>  {
> +	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();
> +}
> +
> +void setup_apic_flat_routing(void)

static?

YH
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