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Shutemov" To: Mike Rapoport Cc: Mike Rapoport , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org Subject: Re: [LSF/MM/BPF TOPIC] Restricted kernel address spaces Message-ID: <20200217103457.c3bmwp43fpa3ho4f@box> References: <20200206165900.GD17499@linux.ibm.com> <20200207173909.e5gtjys7q4ieh2fv@box> <20200211172047.GA24237@hump> <20200211215334.bftqnru57mv5bcza@box> <20200216063504.GA22092@hump.haifa.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200216063504.GA22092@hump.haifa.ibm.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.002531, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Feb 16, 2020 at 08:35:04AM +0200, Mike Rapoport wrote: > > BTW, with clarified scope of the AMD Erratum, I believe we can implement > > "collapse" for direct mapping. Willing to try? > > My initial plan was to use a pool of large pages to satisfy "secret" > allocation requests. Whenever a new large page is allocated for that pool, > it's removed from the direct map without being split into small pages and > then when it would be reinstated back there would be no need to collapse > it. It might be okay. But you likely will have to split 1G pages in direct mapping into 2M. Being able to repare the direct mapping is more generally useful. -- Kirill A. Shutemov