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b=NF+hNjrGDHMWirFNyLpGK+CGY/Wtnrcaz8GKXJy/bE0XGkdVLaecqnHgHaxGfEhML 7jpVM/H7S49o+1K+eHQ2EgfO2HX4uAVtcvGRrWZJiMPUTyBYsPFQrSWaQDyWiksE4I zYCVGwUO0Zy3g+Q9YtT5JjZ6L4/EJc4YcANsfzc5P8J46J4DvIu422Ekpr+LWz/xu5 1tDTRL8fevCgQaBA+DwfgEVIfNxbm2kn1CppO/72VC+Bxe/6aX19AeSe+j5ZVvsX6c jKIeV1sk1Atk76qflMRZe3BT+0W+nn49+KZBrII6YRZh59RXG6gb+f1yfN7sBXtrbi XI5m2BF99M4Cw== Date: Thu, 24 Apr 2025 15:50:52 +0300 From: Leon Romanovsky To: Jason Gunthorpe Cc: Christoph Hellwig , Mika =?iso-8859-1?Q?Penttil=E4?= , Marek Szyprowski , Jens Axboe , Keith Busch , Jake Edge , Jonathan Corbet , Zhu Yanjun , Robin Murphy , Joerg Roedel , Will Deacon , Sagi Grimberg , Bjorn Helgaas , Logan Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, Niklas Schnelle , Chuck Lever , Luis Chamberlain , Matthew Wilcox , Dan Williams , Kanchan Joshi , Chaitanya Kulkarni Subject: Re: [PATCH v9 10/24] mm/hmm: let users to tag specific PFN with DMA mapped bit Message-ID: <20250424125052.GS48485@unreal> References: <0a7c1e06269eee12ff8912fe0da4b7692081fcde.1745394536.git.leon@kernel.org> <7185c055-fc9e-4510-a9bf-6245673f2f92@redhat.com> <20250423181706.GT1213339@ziepe.ca> <36891b0e-d5fa-4cf8-a181-599a20af1da3@redhat.com> <20250423233335.GW1213339@ziepe.ca> <20250424080744.GP48485@unreal> <20250424081101.GA22989@lst.de> <20250424084626.GQ48485@unreal> <20250424120703.GY1213339@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250424120703.GY1213339@ziepe.ca> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 9AD8F4000E X-Stat-Signature: wedxaafd15ysh9w9zge69qzyeommtgz8 X-HE-Tag: 1745499058-59078 X-HE-Meta: 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 9vz6OLNp uxmV5+8YbzI3RALxZMAXpjhhRZoU9oz8dwx6reWb1AN/S/JcydZ0Z00IStGu4slhcYDckhbC3crv2ZnODe6DhNeGxaemfowqWY7WE/tJH09NmBW1+uh/4L8LhsrkM5YZJpzD16TcIQtMbWmhdj3QyarXK54qen9NwTUnuas7arjIzLbb2wRitaIyRTnjOeHT/pHP9LH7o4Ur17z7emTaSJC+fXMPEadbd9R2n+ZUNW2HKMKW+RkTCBPUMnL3HYeKgXzw+ 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 Thu, Apr 24, 2025 at 09:07:03AM -0300, Jason Gunthorpe wrote: > On Thu, Apr 24, 2025 at 11:46:26AM +0300, Leon Romanovsky wrote: > > On Thu, Apr 24, 2025 at 10:11:01AM +0200, Christoph Hellwig wrote: > > > On Thu, Apr 24, 2025 at 11:07:44AM +0300, Leon Romanovsky wrote: > > > > > I see, so yes order occupies 5 bits [-4,-5,-6,-7,-8] and the > > > > > DMA_MAPPED overlaps, it should be 9 not 7 because of the backwardness. > > > > > > > > Thanks for the fix. > > > > > > Maybe we can use the chance to make the scheme less fragile? i.e. > > > put flags in the high bits and derive the first valid bit from the > > > pfn order? > > > > It can be done too. This is what I got: > > Use genmask: I can do it too, will change. > > enum hmm_pfn_flags { > HMM_FLAGS_START = BITS_PER_LONG - PAGE_SHIFT, > HMM_PFN_FLAGS = GENMASK(BITS_PER_LONG - 1, HMM_FLAGS_START), > > /* Output fields and flags */ > HMM_PFN_VALID = 1UL << HMM_FLAGS_START + 0, > HMM_PFN_WRITE = 1UL << HMM_FLAGS_START + 1, > HMM_PFN_ERROR = 1UL << HMM_FLAGS_START + 2, > HMM_PFN_ORDER_MASK = GENMASK(HMM_FLAGS_START + 7, HMM_FLAGS_START + 3), > > /* Input flags */ > HMM_PFN_REQ_FAULT = HMM_PFN_VALID, > HMM_PFN_REQ_WRITE = HMM_PFN_WRITE, > }; > > Jason