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bh=L2BFlblrmbFXqUaTey2eurponU1/HozmOHiptGPCgJU=; h=Date:From:To:Subject:In-Reply-To:References:From; b=Lhld3ynB1F24353J+r6elbc6+ySKg6pkyoRFOb87z2RhCbb3S23Zt7v+kQ/F5Mf9C bwxSC7+rarhTpNGWyNWTyNmHf1l4u5Z4Bs7C+jEqQp+B6hTKNrd5Tc2Qlmk/AwCiUG CTx22wc5nchRuxQIbX/pBAmTSXZy/dJAnhpkrcBI= Date: Sun, 16 Apr 2023 11:39:44 -0700 From: Andrew Morton To: "buddy.zhang" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Venkatesh Pallipadi , Suresh Siddha , Juergen Gross , Dan Williams , Konstantin Khlebnikov Subject: Re: [PATCH] mm: Keep memory type same on DEVMEM Page-Fault Message-Id: <20230416113944.c9b50a76a98b9e7c974cfac9@linux-foundation.org> In-Reply-To: <20230412142236.407d6d0e6d90232da004980e@linux-foundation.org> References: <20230319033750.475200-1-buddy.zhang@biscuitos.cn> <20230412142236.407d6d0e6d90232da004980e@linux-foundation.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 2FE7D1C0005 X-Stat-Signature: 97yjhqcqwiswp1t9pz9xi37fd8jgm89r X-HE-Tag: 1681670386-742135 X-HE-Meta: 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 4pdyrn0y FvnbH91EzM87MIhfx59cflhsWTnbLcvdByRRsgrf9XV9u9lQlsIKH1ntVSYCAUFpQFr2IHB29emsFUovN2nZlOjdPF2YaCxqmkPpoiqkPgxLeUoExvDyh9e0blpryCW9Xz2qI+N/rEZagttMga7mTgpH2eB/SYUUvKbvJvCpgyRdYzDSKLibquCGiB5AHD5hznjxMcI7kJyLGKMJMsg5C/27vr8XsyYC44dS8AgOQHrE/rInTeb20wrRH2qgvQASTKpiG3TnkBCAJ++Qisq+sZ+TPzB7P4QvFHc6CNpWL647okZJRsoQYjg8L0SvxpqPz9qRIUaZzPuBZxpKwNv5FMdzSOfmeCEzfbUtWzsNjVvgsvjXRW4b4FYwnBTnWj3FnXOxeDGedaGGPlEmSYyO7d27yQQ== 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: On Wed, 12 Apr 2023 14:22:36 -0700 Andrew Morton wrote: > On Sun, 19 Mar 2023 11:37:50 +0800 "buddy.zhang" wrote: > > > On X86 architecture, supports memory type on Page-table, such as > > PTE is PAT/PCD/PWD, which can setup up Memory Type as WC/WB/WT/UC etc. > > Then, Virtual address from userspace or kernel space can map to > > same physical page, if each page table has different memory type, > > then it's confused to have more memory type for same physical page. > > Thanks. Nobody has worked on this code for a long time. I'll cc a few > folks who may be able to comment. > Well that didn't go very well. Buddy, can you please explain what are the user-visible effects of the bug? Does the kernel crash? Memory corruption, etc? Thanks.