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Sun, 22 Dec 2024 04:05:33 -0800 (PST) Received: from [192.168.0.109] ([59.188.211.160]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-219dc9716b3sm56358175ad.90.2024.12.22.04.05.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 22 Dec 2024 04:05:32 -0800 (PST) Message-ID: Date: Sun, 22 Dec 2024 20:05:28 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 6/6] arm64/mm: Drop configurable 48-bit physical address space limit Content-Language: en-MW To: Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel , Catalin Marinas , Will Deacon , Marc Zyngier , Mark Rutland , Ryan Roberts , Anshuman Khandual , Kees Cook , Quentin Perret , asahi@lists.linux.dev References: <20241212081841.2168124-8-ardb+git@google.com> <20241212081841.2168124-14-ardb+git@google.com> From: Nick Chan In-Reply-To: <20241212081841.2168124-14-ardb+git@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Ard, On 12/12/2024 16:18, Ard Biesheuvel wrote: > From: Ard Biesheuvel > > Currently, the maximum supported physical address space can be > configured as either 48 bits or 52 bits. The only remaining difference > between these in practice is that the former omits the masking and > shifting required to construct TTBR and PTE values, which carry bits #48 > and higher disjoint from the rest of the physical address. > > The overhead of performing these additional calculations is negligible, > and so there is little reason to retain support for two different > configurations, and we can simply support whatever the hardware > supports. I am seeing a boot failure on Apple iPad 7 which uses CONFIG_ARM64_16K=y after this change in linux-next as commit 32d053d6f5e9, with nothing appearing on serial console with earlycon enabled unless I set CONFIG_ARM64_VA_BITS_52=y. Reverting this patch makes the kernel work again. Nick Chan