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c=relaxed/simple; d=linux-foundation.org; s=korg; t=1687205658; bh=LxetqB1eFRX4wGu2zVQqDsDxwolvc4APmEuYLkFMCmE=; h=Date:From:To:Subject:In-Reply-To:References:From; b=cuIej+npfo3jZNQZFCrsF9g+OpDCyJwyFzShEHKiQJ0CGUn3ORRX/MyxVhNzVMlll WxEJxgYhvDx6nwiZR3ggLNrdFfUx3dX2WxsSyebm2apYAs+jGtCOHAdqnDyL4MmMsL P9O/yaGQs/vlVsB8r6Pp+NY9wMT+PabeSOAzklhQ= Date: Mon, 19 Jun 2023 13:14:17 -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: <20230619131417.42d4e73d1b7669162ea44e29@linux-foundation.org> In-Reply-To: <20230416113944.c9b50a76a98b9e7c974cfac9@linux-foundation.org> References: <20230319033750.475200-1-buddy.zhang@biscuitos.cn> <20230412142236.407d6d0e6d90232da004980e@linux-foundation.org> <20230416113944.c9b50a76a98b9e7c974cfac9@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (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-Rspamd-Queue-Id: DC5B81C0004 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: n6q16zct1s1heaob6fm84dhdyzdb7iq5 X-HE-Tag: 1687205659-972856 X-HE-Meta: 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 +raB5ON6 wbSbBxoyFP0web8rRWSGOUQVj3U2McWtjo/NUq9TGLD1qhuMH4mpc2nTVdNM8SQ80Ozue+VgaaA/Yw1jZ8Ee16gUJlmNosD1OCHJq97VYlzXylchmUynfERsiJHrw29cwuehz0MNdmTzFQc6qpa8RnUjsOQcd5RbllfsyZdCzwNEXrgi0ZFDemwdy2uJOSCr819ej0PPKGW0r9vbc0HKM/3DlNWEPYKzVrn6BCOAPoqYDOKgabRBWBCQ5eYOEvo2QNUD/n80NUBAOJajxyNHuER7moWd/qCIukYIZ5682F6aFPB5qjVIdIZ87Eq/qe7+qVuGfvNss1EGRqeDMeY+VLsCBDT0RaR6FL/JFx3NsibuKRVqFVpiYVeLF9Mhd+F1qZFIL4mrF81ay1gpzh3OPEcKuhWnyYYyQiMNga44Hyk/H29k= 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 Sun, 16 Apr 2023 11:39:44 -0700 Andrew Morton wrote: > 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. > Anyone?