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Thu, 04 Jun 2026 08:12:22 -0700 (PDT) Date: Thu, 4 Jun 2026 17:11:57 +0200 In-Reply-To: <20260604151151.150377-7-ardb+git@google.com> Mime-Version: 1.0 References: <20260604151151.150377-7-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=2216; i=ardb@kernel.org; h=from:subject; bh=kV5OmQpXjgFAS7tCAScTDlrNCgx2UTozsq6mIJLDLaw=; b=owGbwMvMwCVmkMcZplerG8N4Wi2JIUtx6oHaU/ozd+7jFmBSUJq87skO7VmvdH5vr4uzO/6a/ /8qmZMZHaUsDGJcDLJiiiwCs/++23l6olSt8yxZmDmsTCBDGLg4BWAiN04w/M+bulX5sH7iIYlv m9auPOww+5Ogbav4KsNWhoy7ydPPZ7cx/DMNen1ptYP/+hXK7y+dj7zCqlgRIvO9IfjDscc8ne8 UWhgB X-Mailer: git-send-email 2.54.0.1032.g2f8565e1d1-goog Message-ID: <20260604151151.150377-12-ardb+git@google.com> Subject: [PATCH v2 5/5] arm64: mm: Defer remap of linear alias of data/bss From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, Ard Biesheuvel , Kevin Brodsky , Mark Brown , Marc Zyngier Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260604_161225_857193_6C2FCE1E X-CRM114-Status: GOOD ( 15.00 ) 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 From: Ard Biesheuvel Marking the linear alias of data/bss invalid involves calling set_memory_valid(), which calls split_kernel_leaf_mapping() under the hood. On BBML2_NOABORT capable systems, this may result in the need to allocate page tables at a time when the generic memory allocation APIs are not yet available, resulting in a splat like WARNING: arch/arm64/mm/mmu.c:821 at split_kernel_leaf_mapping+0x15c/0x170, CPU#0: swapper/0 Modules linked in: CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.1.0-rc6 #1 PREEMPT(undef) pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : split_kernel_leaf_mapping+0x15c/0x170 lr : update_range_prot+0x40/0x128 sp : ffffc99ad3863c80 ... Call trace: split_kernel_leaf_mapping+0x15c/0x170 (P) update_range_prot+0x40/0x128 set_memory_valid+0x94/0xe0 mark_linear_data_alias_valid+0x54/0x68 map_mem+0x1fc/0x240 paging_init+0x48/0x210 setup_arch+0x274/0x338 start_kernel+0x98/0x538 __primary_switched+0x88/0x98 as reported by CKI automated testing. So defer the boot-time call to mark_linear_data_alias_valid() to a later time when page allocations can be made normally. Signed-off-by: Ard Biesheuvel --- arch/arm64/mm/mmu.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index d68e691c093a..3134f1c1097c 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1095,6 +1095,9 @@ void __init mark_linear_text_alias_ro(void) (unsigned long)__init_begin - (unsigned long)_text, PAGE_KERNEL_RO); + /* Map the kernel data/bss as invalid in the linear map */ + mark_linear_data_alias_valid(false); + /* * Register a PM notifier to remap the linear alias of data/bss as * valid read-only before hibernation. This is needed because the @@ -1237,9 +1240,6 @@ static void __init map_mem(void) __map_memblock(start, end, pgprot_tagged(PAGE_KERNEL), flags); } - - /* Map the kernel data/bss as invalid in the linear map */ - mark_linear_data_alias_valid(false); } void mark_rodata_ro(void) -- 2.54.0.1032.g2f8565e1d1-goog