linux-kernel - Re: [PATCH 1/2] x86/xen/apic: Work with UP, non-SMP 32-bit kernels.

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Date:	Wed, 4 Mar 2015 09:33:01 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	<boris.ostrovsky@...cle.com>, <xen-devel@...ts.xenproject.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86/xen/apic: Work with UP, non-SMP 32-bit kernels.

On 03/03/15 20:29, Konrad Rzeszutek Wilk wrote:
> On Tue, Mar 03, 2015 at 03:20:41PM -0500, Konrad Rzeszutek Wilk wrote:
>> Most of the APIC code that use APIC_LDR is not used on
>> 64-bit. On 32-bit it is bit of an hack - and the mechanism
>> it is uses is to "setup" the APIC_LDR via apci->init_apic_ldr
>> (which we set to NULL) and then use apic->x86_32_early_logical_apicid
>> to get an CPU to APIC ID mapping and also apic->read to match
>> the APIC_LDR.
>>
>> The 'x86_32_early_logical_apicid' is called from 'setup_local_APIC'
>> which is called from the following functions:
>>  - start_secondary ->smp_callin -> apic_ap_setup [not called on PV]
>>  - native_smp_prepare_cpus -> apci_bsp_setup [not called on PV]
>>  - up_late_init -> APIC_init_uniprocessor -> apic_bsp_setup ->setup_local_APIC
>>    [called on PV with CONFIG_SMP not defined, CONFIG_X86_32 and UP kernel]
>>
>> This patch fixes the build issue and also allows the bootup
>> to continue without warnings.
>>
>> Reported-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>> ---
>>  arch/x86/xen/apic.c | 15 ++++++++++++---
>>  1 file changed, 12 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c
>> index 86bea3e..de1c74d 100644
>> --- a/arch/x86/xen/apic.c
>> +++ b/arch/x86/xen/apic.c
>> @@ -56,7 +56,10 @@ static u32 xen_apic_read(u32 reg)
>>  
>>  	if (reg == APIC_LVR)
>>  		return 0x10;
>> -
>> +#ifdef CONFIG_X86_32
>> +	if (reg == APIC_LDR)
>> +		return SET_APIC_LOGICAL_ID(1UL << smp_processor_id());
>> +#endif
>>  	if (reg != APIC_ID)
>>  		return 0;
>>  
>> @@ -117,6 +120,12 @@ static int xen_phys_pkg_id(int initial_apic_id, int index_msb)
>>  	return initial_apic_id >> index_msb;
>>  }
>>  
>> +static int xen_x86_32_early_logical_apicid(int cpu)
>> +{
>> +	/* Match with APIC_LDR read. Otherwise setup_local_APIC complains. */
>> +	return 1 << cpu;
>> +}
>> +
> 
> Argh. That should have been wrapped with CONFIG_X86_32 otherwise it will complain
> on 64-bit (not used.. etc).
> 
> David, I can commit it in and fix it up.

Can you fold all fixes these into the original patch?  No need to
unnecessary break bisection.

David
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