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Howlett" , Vlastimil Babka , Lorenzo Stoakes , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Huacai Chen , WANG Xuerui , Russell King , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , "David S. Miller" , Andreas Larsson , Shuah Khan , Alexandre Ghiti , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Palmer Dabbelt , linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH 00/16] mm: Introduce MAP_BELOW_HINT Message-ID: References: <20240827-patches-below_hint_mmap-v1-0-46ff2eb9022d@rivosinc.com> <4219f619-4b32-40bc-85b8-cb11d76fde98@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4219f619-4b32-40bc-85b8-cb11d76fde98@intel.com> X-Rspamd-Queue-Id: 7785AC0007 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 4fbmeii3zn8wgbyj6cpjggewb5o3yxke X-HE-Tag: 1724979634-377323 X-HE-Meta: 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 s6ahqSYd gRq2lMmquCLHmA2IHOBTTfLtZYrf/x4FwLtyAHAiUNhBevymO7G7Qmw2iLN7vnGLnSU0/tvOajxoVCKOLv5GHl4GUgWRQftoqD4aEiI5jQeCLqAL+ORiy54GH4t10MZURGRKmn2sKTo0Z8wAsex1bwx0PgmBPT3PhjoWOOKBoevyl9mGlnzXCZauWomyqZYewu2wGKm2NRh9LEDvglc9oXckMcL3z6kVi0Rdbr6kf5xwPquFWWiQb0GvgNxa+4FLIYOdY2+KfrJBT370zzclfzjCO4c82yLcnE5HvCBYlK7kxf4uiHcc/kNQgHGgZz/rYKpZfmXI89IFM2J4GEAnCRnU0pjjCaiFg306IplI3wfsaU3c3Al7xc9TVKXGWn28E2EauUR0K6ubpS72jS3FBzcE4sw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000087, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 29, 2024 at 09:54:08AM -0700, Dave Hansen wrote: > On 8/28/24 13:15, Charlie Jenkins wrote: > > A way to restrict mmap() to return LAM compliant addresses in an entire > > address space also doesn't have to be mutually exclusive with this flag. > > This flag allows for the greatest degree of control from applications. > > I don't believe there is additionally performance saving that could be > > achieved by having this be on a per address space basis. > > I agree with you in general. The MAP_BELOW_HINT _is_ the most flexible. > But it's also rather complicated. Can you expand upon what you mean by it being complicated? Complicated for the kernel or complicated for a user? > > My _hope_ would be that a per-address-space property could share at > least some infrastructure with what x86/LAM and arm/TBI do to the > address space. Basically put the restrictions in place for purely > software reasons instead of the mostly hardware reasons for LAM/TBI. That is a good point, perhaps that would be a way to hook this into LAM, TBI, and any other architecture's specific address masking feature. - Charlie > > Lorenzo also raised some very valid points about a having a generic > address-restriction ABI. I'm certainly not discounting those concerns. > It's not something that can be done lightly.