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Date:   Tue, 12 Apr 2022 08:21:20 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc:     Christoph Hellwig <hch@lst.de>, iommu@lists.linux-foundation.org,
        x86@kernel.org, Anshuman Khandual <anshuman.khandual@arm.com>,
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Subject: Re: [PATCH 10/15] swiotlb: add a SWIOTLB_ANY flag to lift the low
 memory restriction
Message-ID: <20220412062120.GA7796@lst.de>
References: <20220404050559.132378-1-hch@lst.de> <20220404050559.132378-11-hch@lst.de> <Yk4vfAd0J5u+wUsq@char.us.oracle.com>
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On Wed, Apr 06, 2022 at 08:25:32PM -0400, Konrad Rzeszutek Wilk wrote:
> > diff --git a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
> > index c5228f4969eb2..3b4045d508ec8 100644
> > --- a/arch/powerpc/platforms/pseries/svm.c
> > +++ b/arch/powerpc/platforms/pseries/svm.c
> > @@ -28,7 +28,7 @@ static int __init init_svm(void)
> >  	 * need to use the SWIOTLB buffer for DMA even if dma_capable() says
> >  	 * otherwise.
> >  	 */
> > -	swiotlb_force = SWIOTLB_FORCE;
> > +	ppc_swiotlb_flags |= SWIOTLB_ANY | SWIOTLB_FORCE;
> 
> This is the only place you set the ppc_swiotlb_flags.. so I wonder why
> the '|=' instead of just '=' ?

Preparing for setting others and not clobbering the value.