linux-kernel - Re: [PATCH v2] powerpc: Allow flush_(inval_)dcache

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Message-ID: <bae6de93-f135-68c5-9118-a0732e6de301@c-s.fr>
Date:   Mon, 26 Aug 2019 22:08:26 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alastair D'Silva <alastair@....ibm.com>
Cc:     alastair@...ilva.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linuxppc-dev@...ts.ozlabs.org, Allison Randal <allison@...utok.net>
Subject: Re: [PATCH v2] powerpc: Allow flush_(inval_)dcache_range to work
 across ranges >4GB



Le 26/08/2019 à 18:50, Greg Kroah-Hartman a écrit :
> On Wed, Aug 21, 2019 at 10:19:27AM +1000, Alastair D'Silva wrote:
>> From: Alastair D'Silva <alastair@...ilva.org>
>>
>> The upstream commit:
>> 22e9c88d486a ("powerpc/64: reuse PPC32 static inline flush_dcache_range()")
>> has a similar effect, but since it is a rewrite of the assembler to C, is
>> too invasive for stable. This patch is a minimal fix to address the issue in
>> assembler.
>>
>> This patch applies cleanly to v5.2, v4.19 & v4.14.
>>
>> When calling flush_(inval_)dcache_range with a size >4GB, we were masking
>> off the upper 32 bits, so we would incorrectly flush a range smaller
>> than intended.
>>
>> This patch replaces the 32 bit shifts with 64 bit ones, so that
>> the full size is accounted for.
>>
>> Changelog:
>> v2
>>    - Add related upstream commit
>>
>> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
>> ---
>>   arch/powerpc/kernel/misc_64.S | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
>> index 1ad4089dd110..d4d096f80f4b 100644
>> --- a/arch/powerpc/kernel/misc_64.S
>> +++ b/arch/powerpc/kernel/misc_64.S
>> @@ -130,7 +130,7 @@ _GLOBAL_TOC(flush_dcache_range)
>>   	subf	r8,r6,r4		/* compute length */
>>   	add	r8,r8,r5		/* ensure we get enough */
>>   	lwz	r9,DCACHEL1LOGBLOCKSIZE(r10)	/* Get log-2 of dcache block size */
>> -	srw.	r8,r8,r9		/* compute line count */
>> +	srd.	r8,r8,r9		/* compute line count */
>>   	beqlr				/* nothing to do? */
>>   	mtctr	r8
>>   0:	dcbst	0,r6
>> @@ -148,7 +148,7 @@ _GLOBAL(flush_inval_dcache_range)
>>   	subf	r8,r6,r4		/* compute length */
>>   	add	r8,r8,r5		/* ensure we get enough */
>>   	lwz	r9,DCACHEL1LOGBLOCKSIZE(r10)/* Get log-2 of dcache block size */
>> -	srw.	r8,r8,r9		/* compute line count */
>> +	srd.	r8,r8,r9		/* compute line count */
>>   	beqlr				/* nothing to do? */
>>   	sync
>>   	isync
> 
> I need an ack from the powerpc maintainer(s) before I can take this.

I think you already got an ack (on v1). See 
https://patchwork.ozlabs.org/patch/1147403/#2239663

Christophe