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b=KyDFhaX0ckf5/YrwFt0U5X9+9yhz7wuK1xRDrQby4m9loYda/mWYsYv9SY59N4gJ6 5d073ME7gJ1z9rA31EIzjFcxe4I3AVQIT/2NSGorRpYNEOtT+F8EhM2AZW46Dw/n0Z vaGYR9Xfm5JfGdqLNtiL2cnXXVqj1BrqYqoU5i4BKvOWzGv2Yd7B4cAICNJ5fC+Vc8 uGGjcIe+DLFxmnd3I3SiLsEKP6g/IP4pH72Gg5RuodsraJis5EAIqdG5XWt1P3jcEV Huk4QRaOzR7e3qPnBSCwxW8/GHEjjU+k0tlGpa0pNjQEMA5kAEawmKxX5Pe+HA5fh7 knPyNOYNgXPaA== Date: Fri, 19 Sep 2025 12:27:17 +0100 From: Will Deacon To: Ryan Roberts Cc: catalin.marinas@arm.com, akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, ardb@kernel.org, dev.jain@arm.com, scott@os.amperecomputing.com, cl@gentwo.org, Yang Shi , kernel-team@android.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v8 0/5] arm64: support FEAT_BBM level 2 and large block mapping when rodata=full Message-ID: References: <20250917190323.3828347-1-yang@os.amperecomputing.com> <175822779944.710258.10028837182267037801.b4-ty@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 3E465100004 X-Stat-Signature: 8b4m4gc5psnq3jzh79dyt1fjaepd9yuz X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1758281244-983881 X-HE-Meta: U2FsdGVkX18I5Hcx4l+FGbJUmnLrvx7iMZf10zbePnkIKhosVeIVojeYf3IZ1GYisURzg8McinHpyO5amSuoXkgayqkATxQ+js92pPkV+5m29RY2IwKLF8xbnC/02LHuwCLZ9t+T1ImwvVeFqPvYGIJV6FKwcbOYSQYNb4Pp5PbBFZWMGcW9LbcZTuODD2frgcxgS58o+JAVTpl+4WSGwaF65PUmhaF29TSDgRvCpVQOGgUEJHYYO+drd06HAyCsVX19Jm91dcOfu4uAMKP+us0FfLD7ynjz3vonZiUAc3AWkWIpug4aQbCO38k0mjqbmqi9oyf1zof72cvQLRDcjkJEceQWJK+7hB9UBjb9r1VpH33hgv5Q0FKdC1jHz8iYIGTR/OxkV262kI8qrddqXn1VKhveePXJ5kaS1LaqHN1+88STgRrXxm6ccY4JZ4AGQ7GdNvE2NDkfLQ3zF/zi7w1Bj9rl/s/kDzPT1PsT6ubzxWuOgItaS6ydASu4pI836SWYMPSwUPsMb+VVwFqyZPstgtX08Sv9MTy+Edu2UfZ1SIVp5ObAs6vIsBwmjPza5lXAIrZN+gRgasOz4UFoq+biqqzusy9tQSR5hcm0qt1h+d3J0tcqVPb1MtAQDIyO9+Fr69YbLwZocNXEzRb8YpsSKE1LD6gLJlp4NCn/ayyFkrd7r44lcPvLbKNMDcRCmfJW++jgjigUIFR0ACxo8mGcDjt/NKmrabtLgiW7il6lNl6gHvbOpjfTn3EBRSFBwMD76qmcd73MQ6kr5ECON//WsmsIa8t8DRAkzTkX+HmsJ91Bu6fT5SBLDBXtbz3yV/xpfHEQSLnKrIsO+nGeGMB3gnDSUzFd8uGEIssIQf9VpVQN66PuVI6YbtqTVA2DjadFTxt0mzVa4gkJhA4tO/TqphwdH8AyGFSTeWKJeb/Iv9ugXrwl9k1Y2Xtd+7fEPQXcNOGo2TX3MU+Hys5 8s9ctJeh Ie8ah96iQSLc+tsfgVWnwsMB6ImJkCn/J0NdrkX8pYiHwj/qiZw7aLdiQKKtGALefQnGX8k9t+h9LycjyfZEfXloGJIjy3bjQ1xqt4SeEtPeoz6x2o3kQwPfzjlaqR2i4/Duf+lKb6Z/peDfcLKRoEpUS4aL50eDCZoBTQPRL3EUiIHy6KsuR6HAkPL7EdEEUOWVxceuDlooJaGqw9ETG5KHpAYQLXF+rqOdndQl+9ndzdCwOJM+848aUpQCfwGoJm8Fn9GOLssnYJsK1WaIxkHQAzeugSk7z/VzQ8DsWD7Tazsg4eREIlS8SOAIwOErPdTMj 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: List-Subscribe: List-Unsubscribe: On Fri, Sep 19, 2025 at 11:08:47AM +0100, Ryan Roberts wrote: > On 18/09/2025 22:10, Will Deacon wrote: > > On Wed, 17 Sep 2025 12:02:06 -0700, Yang Shi wrote: > >> On systems with BBML2_NOABORT support, it causes the linear map to be mapped > >> with large blocks, even when rodata=full, and leads to some nice performance > >> improvements. > >> > >> Ryan tested v7 on an AmpereOne system (a VM with 12G RAM) in all 3 possible > >> modes by hacking the BBML2 feature detection code: > >> > >> [...] > > > > Applied patches 1 and 3 to arm64 (for-next/mm), thanks! > > > > [1/5] arm64: Enable permission change on arm64 kernel block mappings > > https://git.kernel.org/arm64/c/a660194dd101 > > [3/5] arm64: mm: support large block mapping when rodata=full > > https://git.kernel.org/arm64/c/a166563e7ec3 > > > > I also picked up the BBML allow-list addition (second patch) on > > for-next/cpufeature. > > > > The fourth patch ("arm64: mm: split linear mapping if BBML2 unsupported > > on secondary CPUs") has some really horrible conflicts. These are partly > > due to some of the type cleanups on for-next/mm but I think mainly due > > to Kevin's kpti rework that landed after -rc1. > > Thanks Will, although I'm nervous that without this patch, some platforms might > not boot; Wikipedia tells me that there are some Google, Mediatek and Qualcomm > SoCs that pair X4 CPUs (which is on the BBML2_NOABORT allow list) with A720 > and/or A520 (which are not). See previous mail at [1]. I'd be surprised if these SoCs are booting on the X4 but who knows. Lemme have another look at applying the patch with fresh eyes, but I do wonder whether having X4 on the allow list really makes any sense. Are there any SoCs out there that _don't_ pair it with CPUs that aren't on the allow list? (apologies for the double negative). Will