linux-kernel - Re: [PATCH v2 2/2] MIPS: CPS: Copy EVA configuration when starting secondary VPs.

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Date:	Thu, 19 May 2016 08:06:38 +0100
From:	Matt Redfearn <matt.redfearn@...tec.com>
To:	Paul Burton <paul.burton@...tec.com>
CC:	Ralf Baechle <ralf@...ux-mips.org>, <linux-mips@...ux-mips.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] MIPS: CPS: Copy EVA configuration when starting
 secondary VPs.

Hi Paul,

On 18/05/16 23:34, Paul Burton wrote:
> On Wed, May 18, 2016 at 05:12:36PM +0100, Matt Redfearn wrote:
>> When starting secondary VPEs which support EVA and the SegCtl registers,
>> copy the memory segmentation configuration from the running VPE to ensure
>> that all VPEs in the core have a consistent virtual memory map.
>>
>> The EVA configuration of secondary cores is dealt with when starting the
>> core via the CM.
>>
>> Signed-off-by: Matt Redfearn <matt.redfearn@...tec.com>
>> ---
>>
>> Changes in v2:
>> - Skip check for config3 existing - we know it must to be doing
>> multithreading
>> - Use a unique lable name in the function
>>
>>   arch/mips/kernel/cps-vec.S | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/arch/mips/kernel/cps-vec.S b/arch/mips/kernel/cps-vec.S
>> index ac81edd44563..f8eae9189e38 100644
>> --- a/arch/mips/kernel/cps-vec.S
>> +++ b/arch/mips/kernel/cps-vec.S
>> @@ -431,6 +431,21 @@ LEAF(mips_cps_boot_vpes)
>>   	mfc0	t0, CP0_CONFIG
>>   	mttc0	t0, CP0_CONFIG
>>   
>> +	/*
>> +	 * Copy the EVA config from this VPE if the CPU supports it.
>> +	 * CONFIG3 must exist to be running MT startup - just read it.
>> +	 */
>> +	mfc0	t0, CP0_CONFIG, 3
>> +	and	t0, t0, MIPS_CONF3_SC
> Tiny nit - I'd prefer "andi" here since we're using an immediate. The
> assembler will figure it out though, so it's not a big deal.
Yeah, I would have too, and I did have that to start off with, but the 
assembler gave me:
arch/mips/kernel/cps-vec.S: Assembler messages:
arch/mips/kernel/cps-vec.S:450: Error: operand 3 out of range `andi 
$8,$8,((1)<<25)'
So I fell back to letting the assembler generate the LUI and AND.
>
> For both in the series:
>
>      Reviewed-by: Paul Burton <paul.burton@...tec.com>
Thanks Paul,
Matt

> Thanks,
>      Paul
>
>> +	beqz	t0, 3f
>> +	 nop
>> +	mfc0    t0, CP0_SEGCTL0
>> +	mttc0	t0, CP0_SEGCTL0
>> +	mfc0    t0, CP0_SEGCTL1
>> +	mttc0	t0, CP0_SEGCTL1
>> +	mfc0    t0, CP0_SEGCTL2
>> +	mttc0	t0, CP0_SEGCTL2
>> +3:
>>   	/* Ensure no software interrupts are pending */
>>   	mttc0	zero, CP0_CAUSE
>>   	mttc0	zero, CP0_STATUS
>> -- 
>> 2.5.0
>>