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Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Masami Hiramatsu , Mathieu Desnoyers , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, iommu@lists.linux.dev, virtualization@lists.linux.dev, kasan-dev@googlegroups.com, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 0/8] dma-mapping: migrate to physical address-based API Message-ID: <20250731060117.GR402218@unreal> References: <35df6f2a-0010-41fe-b490-f52693fe4778@samsung.com> <20250627170213.GL17401@unreal> <20250630133839.GA26981@lst.de> <69b177dc-c149-40d3-bbde-3f6bad0efd0e@samsung.com> <20250730134026.GQ402218@unreal> <20250730142818.GL26511@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250730142818.GL26511@ziepe.ca> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D198DC0006 X-Stat-Signature: gpwxtidffrk5fikrnz76m6on3uwk1hst X-Rspam-User: X-HE-Tag: 1753941683-815726 X-HE-Meta: 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 SEGlJwVA OT//3mIPbDw6qqa0mQvKvNSIha2H6TxUF+i7JyYWPx+PCee7Wq4EuiHgf59YnwGuH5u0cIMJXf0ebAv3fJVy+lzP9DHpJDSbA59TzWJDtKsSTvhkR15owjiltj55zayO4215zbJrKWtnPto4MHaehMxCbQpTsW4pp5GBoTAiroTIPYtcnUir2WR1ABxm4LBFIpaHQLwMn8ROozRiXsPBWWh0fC7ZOCo3MH+kFoxmS7cFfcAPtyTYsvEjcTxtFA+EXir4i X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jul 30, 2025 at 11:28:18AM -0300, Jason Gunthorpe wrote: > On Wed, Jul 30, 2025 at 04:40:26PM +0300, Leon Romanovsky wrote: <...> > > The most reasonable way to prevent DMA_ATTR_SKIP_CPU_SYNC leakage is to > > introduce new DMA attribute (let's call it DMA_ATTR_MMIO for now) and > > pass it to both dma_map_phys() and dma_iova_link(). This flag will > > indicate that p2p type is PCI_P2PDMA_MAP_THRU_HOST_BRIDGE and call to > > right callbacks which will set IOMMU_MMIO flag and skip CPU sync, > > So the idea is if the memory is non-cachable, no-KVA you'd call > dma_iova_link(phys_addr, DMA_ATTR_MMIO) and dma_map_phys(phys_addr, > DMA_ATTR_MMIO) ? Yes > > And then internally the dma_ops and dma_iommu would use the existing > map_page/map_resource variations based on the flag, thus ensuring that > MMIO is never kmap'd or cache flushed? > > dma_map_resource is really then just > dma_map_phys(phys_addr, DMA_ATTR_MMIO)? > > I like this, I think it well addresses the concerns. Yes, I had this idea and implementation before. :( > > Jason >