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[142.162.115.133]) by smtp.gmail.com with ESMTPSA id w188sm17159979qkc.19.2021.02.08.10.51.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Feb 2021 10:51:33 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1l9BdF-0052Tc-8p; Mon, 08 Feb 2021 14:51:33 -0400 Date: Mon, 8 Feb 2021 14:51:33 -0400 From: Jason Gunthorpe To: Peter Xu , dan.j.williams@intel.com Cc: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, Andrew Morton Subject: Re: [PATCH 0/2] KVM: do not assume PTE is writable after follow_pfn Message-ID: <20210208185133.GW4718@ziepe.ca> References: <20210205103259.42866-1-pbonzini@redhat.com> <20210205181411.GB3195@xz-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210205181411.GB3195@xz-x1> 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 Fri, Feb 05, 2021 at 01:14:11PM -0500, Peter Xu wrote: > But I do have a question on why dax as the only user needs to pass in the > notifier to follow_pte() for initialization. Not sure either, why does DAX opencode something very much like page_mkclean() with dax_entry_mkclean()? Also it looks like DAX uses the wrong notifier, it calls MMU_NOTIFY_CLEAR but page_mkclean_one() uses MMU_NOTIFY_PROTECTION_PAGE for the same PTE modification sequence?? page_mkclean() has some technique to make the notifier have the right size without becoming entangled in the PTL locks.. Jason