From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Wed, 10 Jan 2018 17:10:02 +0000 Subject: [PATCH 21/22] arm64: replace ZONE_DMA with ZONE_DMA32 In-Reply-To: <20180110155546.GB18903@lst.de> References: <20180110080932.14157-1-hch@lst.de> <20180110080932.14157-22-hch@lst.de> <0371cef8-d980-96da-9cb5-3609c39be18a@arm.com> <20180110155517.GA18774@lst.de> <20180110155546.GB18903@lst.de> Message-ID: <3c3263ca-b0ab-654a-d67d-f5ff5e31280c@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 10/01/18 15:55, Christoph Hellwig wrote: > On Wed, Jan 10, 2018 at 04:55:17PM +0100, Christoph Hellwig wrote: >> On Wed, Jan 10, 2018 at 12:58:14PM +0000, Robin Murphy wrote: >>> On 10/01/18 08:09, Christoph Hellwig wrote: >>>> arm64 uses ZONE_DMA for allocations below 32-bits. These days we >>>> name the zone for that ZONE_DMA32, which will allow to use the >>>> dma-direct and generic swiotlb code as-is, so rename it. >>> >>> I do wonder if we could also "upgrade" GFP_DMA to GFP_DMA32 somehow when >>> !ZONE_DMA - there are almost certainly arm64 drivers out there using a >>> combination of GFP_DMA and streaming mappings which will no longer get the >>> guaranteed 32-bit addresses they expect after this. I'm not sure quite how >>> feasible that is, though :/ >> >> I can't find anything obvious in the tree. The alternative would be >> to keep ZONE_DMA and set ARCH_ZONE_DMA_BITS. >> >>> That said, I do agree that this is an appropriate change (the legacy of >>> GFP_DMA is obviously horrible), so, provided we get plenty of time to find >>> and fix the fallout when it lands: >>> >>> Reviewed-by: Robin Murphy >> >> I was hoping to get this into 4.15. What would be proper time to >> fix the fallout? > > Err, 4.16 of course. Hee hee - cramming it into 4.15 is exactly what I wouldn't want to do, even if Linus would accept it :) Landing it this merge window for 4.16-rc1 sounds good if we can manage that. Robin.