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b=LKxqJIH2gitAORyRjRTVUOwJedMlXeBfjfYhSaPvC9muinRajK8LMTESWiHvpKguv 2himUzCHPxi9e2BUWe6lTa1DAV/gPbrHcHGPHIv0BxugJyQ9h+XavqGxZ0EB5n9CLD bEFrYwuDLu8c7wt+are2vfq1QwixbaLk8k6ZqYz9+5TJArSwW3T/0ACshg+pZOUdx1 ZHZx0U5AXWGiOIEI1zJJ3gHp1GOTymhXXuwaBYcu2AiUXf6LQvtKG5kGOltn+XG7+f iJvzhQxhYf+2WAbH/lA6aicPsVoJB27UPTb53VWd2w9FqchqEJNqj4wu49rX1QcvUs WZNjI10qgI5Fw== Date: Sat, 30 Sep 2023 10:02:35 +0100 From: Conor Dooley To: Sami Tolvanen Cc: Kees Cook , Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Morton , linux-mm@kvack.org, linux-riscv@lists.infradead.org, llvm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] riscv: mm: Update mmap_rnd_bits_max Message-ID: <20230930-emporium-share-2bbdf7074e54@spud> References: <20230929211155.3910949-4-samitolvanen@google.com> <20230929211155.3910949-6-samitolvanen@google.com> <202309291452.66ED9B4D83@keescook> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ZyDAWSEjMDJNp7Wh" Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 383852000A X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 4gooriw7m5qfkr56rsyioziuacpu76m7 X-HE-Tag: 1696064564-657926 X-HE-Meta: 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 BCrNsZvZ GupIf1ws0EH+42UXvV6sLMmwTNbDy+mpvz5UEXDZJq0KKoFobU48FYRhWDDZUoWP/cifgHwxxHaDqFzR/v7NaFpj9G4TMc6Ml5zj+yoCOU2QFrtprxCq7mtvOsp/I0nVmmsU8+Vm25cWTgd8ZuSGicttu8H0F/YInAVWgpnxaYOIZVKvGCpCRFUujzqWifBdTrU9pO3nX/dgW0+HkrFOf+RTW3DeCW/8fiBFPmcu7wM61Ya7Ok2lG8iBOz8v2gjemYDVQsfP4cFbnPy8PlpI9G9iSubCH/of9BayARsj1FnL3bvUJKMpu1SpzQ7FsE3sRqOyOkqCxllFgsr6aX1CfJaQ6fXmDrgWOlZ9Qvs9Vzs59eKKgYoksgPrAoDfw3ih/vOI9qkjALYu1VxjhKQHu2KII2auf5l3hK/F5c1giUO4v2QY= 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: --ZyDAWSEjMDJNp7Wh Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Sep 29, 2023 at 03:52:22PM -0700, Sami Tolvanen wrote: > On Fri, Sep 29, 2023 at 2:54=E2=80=AFPM Kees Cook = wrote: > > > > On Fri, Sep 29, 2023 at 09:11:58PM +0000, Sami Tolvanen wrote: > > > ARCH_MMAP_RND_BITS_MAX is based on Sv39, which leaves a few > > > potential bits of mmap randomness on the table if we end up enabling > > > 4/5-level paging. Update mmap_rnd_bits_max to take the final address > > > space size into account. This increases mmap_rnd_bits_max from 24 to > > > 33 with Sv48/57. > > > > > > Signed-off-by: Sami Tolvanen > > > > I like this. Is RISCV the only arch where the paging level can be chosen > > at boot time? >=20 > I haven't seen this elsewhere, but I also haven't looked at all the > other architectures that closely. arm64 does something interesting > with ARM64_VA_BITS_52, but I think we can still handle that in > Kconfig. AFAIU, x86-64 can do this also: no4lvl [RISCV] Disable 4-level and 5-level paging modes. Forces kernel to use 3-level paging instead. no5lvl [X86-64,RISCV] Disable 5-level paging mode. Forces kernel to use 4-level paging instead. --ZyDAWSEjMDJNp7Wh Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZRfkKwAKCRB4tDGHoIJi 0sckAP96xMeKJdlGIablTffmHoXBsU3nIZz+lu2Vm/HAnLMEKAD+Nxq+WTdOPyHE Tx+O88xAJtz6dMJb3se92VlCB2vHCQA= =/vk6 -----END PGP SIGNATURE----- --ZyDAWSEjMDJNp7Wh--