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[68.4.215.93]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-30451f3feadsm10921365eec.13.2026.05.25.11.15.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 May 2026 11:15:23 -0700 (PDT) Message-ID: <724e103e-ebc2-403c-887e-d91e403754d9@broadcom.com> Date: Mon, 25 May 2026 11:15:20 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ARM: mm: fix kexec and hibernation with CONFIG_CPU_TTBR0_PAN To: Linus Walleij Cc: linux-arm-kernel@lists.infradead.org, bcm-kernel-feedback-list@broadcom.com, Catalin Marinas , Linus Walleij , Russell King , "Russell King (Oracle)" , Kees Cook , open list References: <20260523000839.430550-1-florian.fainelli@broadcom.com> Content-Language: en-US From: Florian Fainelli Autocrypt: addr=florian.fainelli@broadcom.com; keydata= xsBNBFPAG8ABCAC3EO02urEwipgbUNJ1r6oI2Vr/+uE389lSEShN2PmL3MVnzhViSAtrYxeT M0Txqn1tOWoIc4QUl6Ggqf5KP6FoRkCrgMMTnUAINsINYXK+3OLe7HjP10h2jDRX4Ajs4Ghs JrZOBru6rH0YrgAhr6O5gG7NE1jhly+EsOa2MpwOiXO4DE/YKZGuVe6Bh87WqmILs9KvnNrQ PcycQnYKTVpqE95d4M824M5cuRB6D1GrYovCsjA9uxo22kPdOoQRAu5gBBn3AdtALFyQj9DQ KQuc39/i/Kt6XLZ/RsBc6qLs+p+JnEuPJngTSfWvzGjpx0nkwCMi4yBb+xk7Hki4kEslABEB AAHNMEZsb3JpYW4gRmFpbmVsbGkgPGZsb3JpYW4uZmFpbmVsbGlAYnJvYWRjb20uY29tPsLB IQQQAQgAywUCZWl41AUJI+Jo+hcKAAG/SMv+fS3xUQWa0NryPuoRGjsA3SAUAAAAAAAWAAFr ZXktdXNhZ2UtbWFza0BwZ3AuY29tjDAUgAAAAAAgAAdwcmVmZXJyZWQtZW1haWwtZW5jb2Rp bmdAcGdwLmNvbXBncG1pbWUICwkIBwMCAQoFF4AAAAAZGGxkYXA6Ly9rZXlzLmJyb2FkY29t Lm5ldAUbAwAAAAMWAgEFHgEAAAAEFQgJChYhBNXZKpfnkVze1+R8aIExtcQpvGagAAoJEIEx tcQpvGagWPEH/2l0DNr9QkTwJUxOoP9wgHfmVhqc0ZlDsBFv91I3BbhGKI5UATbipKNqG13Z TsBrJHcrnCqnTRS+8n9/myOF0ng2A4YT0EJnayzHugXm+hrkO5O9UEPJ8a+0553VqyoFhHqA zjxj8fUu1px5cbb4R9G4UAySqyeLLeqnYLCKb4+GklGSBGsLMYvLmIDNYlkhMdnnzsSUAS61 WJYW6jjnzMwuKJ0ZHv7xZvSHyhIsFRiYiEs44kiYjbUUMcXor/uLEuTIazGrE3MahuGdjpT2 IOjoMiTsbMc0yfhHp6G/2E769oDXMVxCCbMVpA+LUtVIQEA+8Zr6mX0Yk4nDS7OiBlvOwE0E U8AbwQEIAKxr71oqe+0+MYCc7WafWEcpQHFUwvYLcdBoOnmJPxDwDRpvU5LhqSPvk/yJdh9k 4xUDQu3rm1qIW2I9Puk5n/Jz/lZsqGw8T13DKyu8eMcvaA/irm9lX9El27DPHy/0qsxmxVmU pu9y9S+BmaMb2CM9IuyxMWEl9ruWFS2jAWh/R8CrdnL6+zLk60R7XGzmSJqF09vYNlJ6Bdbs MWDXkYWWP5Ub1ZJGNJQ4qT7g8IN0qXxzLQsmz6tbgLMEHYBGx80bBF8AkdThd6SLhreCN7Uh IR/5NXGqotAZao2xlDpJLuOMQtoH9WVNuuxQQZHVd8if+yp6yRJ5DAmIUt5CCPcAEQEAAcLB gQQYAQIBKwUCU8AbwgUbDAAAAMBdIAQZAQgABgUCU8AbwQAKCRCTYAaomC8PVQ0VCACWk3n+ obFABEp5Rg6Qvspi9kWXcwCcfZV41OIYWhXMoc57ssjCand5noZi8bKg0bxw4qsg+9cNgZ3P N/DFWcNKcAT3Z2/4fTnJqdJS//YcEhlr8uGs+ZWFcqAPbteFCM4dGDRruo69IrHfyyQGx16s CcFlrN8vD066RKevFepb/ml7eYEdN5SRALyEdQMKeCSf3mectdoECEqdF/MWpfWIYQ1hEfdm C2Kztm+h3Nkt9ZQLqc3wsPJZmbD9T0c9Rphfypgw/SfTf2/CHoYVkKqwUIzI59itl5Lze+R5 wDByhWHx2Ud2R7SudmT9XK1e0x7W7a5z11Q6vrzuED5nQvkhAAoJEIExtcQpvGagugcIAJd5 EYe6KM6Y6RvI6TvHp+QgbU5dxvjqSiSvam0Ms3QrLidCtantcGT2Wz/2PlbZqkoJxMQc40rb fXa4xQSvJYj0GWpadrDJUvUu3LEsunDCxdWrmbmwGRKqZraV2oG7YEddmDqOe0Xm/NxeSobc MIlnaE6V0U8f5zNHB7Y46yJjjYT/Ds1TJo3pvwevDWPvv6rdBeV07D9s43frUS6xYd1uFxHC 7dZYWJjZmyUf5evr1W1gCgwLXG0PEi9n3qmz1lelQ8lSocmvxBKtMbX/OKhAfuP/iIwnTsww 95A2SaPiQZA51NywV8OFgsN0ITl2PlZ4Tp9hHERDe6nQCsNI/Us= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260525_111529_485181_92E16A60 X-CRM114-Status: GOOD ( 18.23 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/25/2026 6:35 AM, Linus Walleij wrote: > Hi Florian, > > thanks for digging in and finding this! > > On Sat, May 23, 2026 at 2:08 AM Florian Fainelli > wrote: > >> Commit 7af5b901e847 ("ARM: 9358/2: Implement PAN for LPAE by TTBR0 >> page table walks disablement") implemented PAN for LPAE kernels by >> setting TTBCR.EPD0 on every kernel entry, disabling TTBR0 page-table >> walks while running in kernel mode. The commit correctly updated >> cpu_suspend() in arch/arm/kernel/suspend.c, but missed two other code >> paths that switch the CPU to the identity mapping before jumping to >> low-PA (TTBR0-range) physical addresses: >> >> 1. setup_mm_for_reboot() in arch/arm/mm/idmap.c, used by the kexec >> reboot path. With TTBCR.EPD0 still set, the subsequent branch to >> the identity-mapped cpu_v7_reset causes a PrefetchAbort because the >> TTBR0 page-table walk needed to resolve the identity-mapped address >> is disabled. This manifests as a hard hang or "bad PC value" panic >> on LPAE kernels booted on CPUs that strictly enforce EPD0 for >> instruction fetch (e.g. Cortex-A53 in AArch32 mode) while the same >> image may accidentally work on Cortex-A15 due to microarchitectural >> differences in EPD0 enforcement. >> >> 2. arch_restore_image() in arch/arm/kernel/hibernate.c, which calls >> cpu_switch_mm(idmap_pgd, &init_mm) directly without going through >> setup_mm_for_reboot(), leaving TTBCR.EPD0 set while the identity >> mapping is active. >> >> Fix both sites by calling uaccess_save_and_enable() before switching >> to the identity mapping, mirroring what the original commit did for >> cpu_suspend(). >> >> Fixes: 7af5b901e847 ("ARM: 9358/2: Implement PAN for LPAE by TTBR0 page table walks disablement") >> Cc: Catalin Marinas >> Cc: Linus Walleij >> Assisted-by: Cursor:claude-sonnet-4.6 >> Signed-off-by: Florian Fainelli > > Reviewed-by: Linus Walleij > > Please put this patch into Russell's patch tracker. Thank you, now done: https://www.armlinux.org.uk/developer/patches/viewpatch.php?id=9476/1 -- Florian