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Fri, 8 Feb 2019 17:02:18 +0000 (GMT) Subject: Re: [PATCH] fbcon: use kvmalloc() for scrollback buffer To: Konstantin Khorenko Cc: "linux-fbdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" From: Bartlomiej Zolnierkiewicz Message-ID: Date: Fri, 8 Feb 2019 18:02:17 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <4eba60c6-4eb8-5a82-f394-307f835f41e1@virtuozzo.com> Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFmplleLIzCtJLcpLzFFi42LZduznOV3pbbExBk2nxC2ufH3PZvF450tW ixN9H1gtLu+aw+bA4nG/+ziTx+dNch6v9x9iDGCO4rJJSc3JLEst0rdL4MrYtXsRS8FSzorj W1YzNTCuZ+9i5OSQEDCRODV1D1sXIxeHkMAKRomNy/awQDhfGCXmf7jGBlIlJPCZUWLTCw6Y jkWrOpkhipYzSvz/fBGq/T2jRP+DC4wgVcICDhL/by4Es0UEDCQe7O9jBSliFjjOKLFk61lW kASbgJXExPZVYEW8AnYSn5f2MoPYLAIqEpN6QFZzcIgKREj0n1GHKBGUODnzCQuIzSngKHFn VxuYzSwgL7H97RywiyQE/rNJrDnTA/Wci8TCnzNZIGxhiVfHt0DFZSROT+5hgWiYzijx5tdS KGc9I1D3MSaIKmuJw8cvsoJcwSygKbF+lz5E2FHi9oxdYGEJAT6JG28FIY7gk5i0bTozRJhX oqNNCKJaTWLDsg1sMGu7dq6EKvGQ2NcbMIFRcRaSz2Yh+WYWwtoFjMyrGMVTS4tz01OLDfNS y/WKE3OLS/PS9ZLzczcxAhPH6X/HP+1g/Hop6RCjAAejEg9vREtsjBBrYllxZe4hRgkOZiUR 3rRNQCHelMTKqtSi/Pii0pzU4kOM0hwsSuK81QwPooUE0hNLUrNTUwtSi2CyTBycUg2Meon8 B7Mm5k3l+vhi1ibNvvb6AJ0IdoFtmeeWrT8Ua+gX0bWid6Mbj/CrgxLnJxsJv2ULs7tuXm22 Runq7UXXs6QljFb4+vBfieB60bFvQ9yC5MrkibHqzROdi5ZxfS7zN14kU1e577v72t/Vony5 fnH3GEPuHX4tefOPt1h/nY07q/7XmmglluKMREMt5qLiRAACXPL2GAMAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFuplkeLIzCtJLcpLzFFi42I5/e/4PV2pbbExBhd/K1tc+fqezeLxzpes Fif6PrBaXN41h82BxeN+93Emj8+b5Dxe7z/EGMAcpWdTlF9akqqQkV9cYqsUbWhhpGdoaaFn ZGKpZ2hsHmtlZKqkb2eTkpqTWZZapG+XoJexa/ciloKlnBXHt6xmamBcz97FyMkhIWAisWhV J3MXIxeHkMBSRonmq7eBHA6ghIzE8fVlEDXCEn+udbFB1LxllJjQdZwJJCEs4CDx/+ZCRhBb RMBA4sH+PlaIol+MEidfzWQHcZgFjjNK/PrwC6yKTcBKYmL7KjCbV8BO4vPSXmYQm0VARWJS zzU2EFtUIELi1sMOFogaQYmTM5+A2ZwCjhJ3drWB2cwC6hJ/5l1ihrDlJba/ncM8gVFwFpKW WUjKZiEpW8DIvIpRJLW0ODc9t9hQrzgxt7g0L10vOT93EyMwKrYd+7l5B+OljcGHGAU4GJV4 eBmaYmOEWBPLiitzDzFKcDArifCmbQIK8aYkVlalFuXHF5XmpBYfYjQFemIis5Rocj4wYvNK 4g1NDc0tLA3Njc2NzSyUxHnPG1RGCQmkJ5akZqemFqQWwfQxcXBKNTBOU0r48Czi/28N0ZnG OjwNFvnXPtf92puqPu8ts+OOpm2fehgfCH3S77PLObsv0i0hh2HbJuPq757mQve3aKZP5V3R lm+in153ec4Nnoy8jV6BS52f7TytErVt1SfxMxK7Vu1de+/6rhciQe/fRL5d8aD7Xoe+a5yY m4F92TRxbdvbBgwRLYlKLMUZiYZazEXFiQBu583poAIAAA== X-CMS-MailID: 20190208170218eucas1p228ec2bb11ff97f28ec70c301e50f6b13 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20181126100342epcas3p12a1e6505ff4b73375ac3fcf5d0355d3f X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20181126100342epcas3p12a1e6505ff4b73375ac3fcf5d0355d3f References: <20181126100253.3299-1-khorenko@virtuozzo.com> <4eba60c6-4eb8-5a82-f394-307f835f41e1@virtuozzo.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/21/2018 11:58 AM, Konstantin Khorenko wrote: > Hi Bartlomiej, > > On 12/20/2018 07:21 PM, Bartlomiej Zolnierkiewicz wrote: >> On 11/26/2018 11:02 AM, Konstantin Khorenko wrote: >>> Scrollback frame buffer is rather big - 32K, >>> so it requires 3rd order page, so let's use kvmalloc() instead of >>> ordinary kmalloc() for it. >> >> Is it actually safe to use non-contiguous memory for softback_buf? > > Well, that's why we need a review. :) :) > i've asked myself same question while fixing this, > i've dig sources a bit and did not find places when softback_buf is provided for DMA, > all other places seems to work with virtual addresses, so there should be no problem. > > Even more i saw a function which mentions that softback might be non-contigious: > > /* As we might be inside of softback, we may work with non-contiguous buffer, > that's why we have to use a separate routine. */ > static void fbcon_invert_region(struct vc_data *vc, u16 * p, int cnt) > > So i think it's safe to use kvmalloc() here. Patch queued for v5.1, thanks. Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics