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[142.162.115.133]) by smtp.gmail.com with ESMTPSA id q55sm2537411qtq.57.2021.02.08.15.26.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Feb 2021 15:26:26 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1l9FvF-0057WX-GA; Mon, 08 Feb 2021 19:26:25 -0400 Date: Mon, 8 Feb 2021 19:26:25 -0400 From: Jason Gunthorpe To: Peter Xu Cc: dan.j.williams@intel.com, 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: <20210208232625.GA4718@ziepe.ca> References: <20210205103259.42866-1-pbonzini@redhat.com> <20210205181411.GB3195@xz-x1> <20210208185133.GW4718@ziepe.ca> <20210208220259.GA71523@xz-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210208220259.GA71523@xz-x1> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 5EA90E0001A9 X-Stat-Signature: r1pi1exz7wgyr7ptuhr9qc165gri61j3 Received-SPF: none (ziepe.ca>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=mail-qk1-f172.google.com; client-ip=209.85.222.172 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1612826786-723659 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 Mon, Feb 08, 2021 at 05:02:59PM -0500, Peter Xu wrote: > On Mon, Feb 08, 2021 at 02:51:33PM -0400, Jason Gunthorpe wrote: > > 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.. > > Right. I guess it's because dax doesn't have "struct page*" on the > back, so it It doesn't? I thought DAX cases did? Jason