From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Jon Medhurst (Tixy)" , Catalin Marinas Subject: [PATCH 3.19 70/75] arm64: Use the reserved TTBR0 if context switching to the init_mm Date: Fri, 10 Apr 2015 15:19:36 +0200 Message-Id: <20150410131711.101670237@linuxfoundation.org> In-Reply-To: <20150410131707.794709951@linuxfoundation.org> References: <20150410131707.794709951@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Catalin Marinas commit e53f21bce4d35a93b23d8fa1a840860f6c74f59e upstream. The idle_task_exit() function may call switch_mm() with next == &init_mm. On arm64, init_mm.pgd cannot be used for user mappings, so this patch simply sets the reserved TTBR0. Reported-by: Jon Medhurst (Tixy) Tested-by: Jon Medhurst (Tixy) Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/mmu_context.h | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -151,6 +151,15 @@ switch_mm(struct mm_struct *prev, struct { unsigned int cpu = smp_processor_id(); + /* + * init_mm.pgd does not contain any user mappings and it is always + * active for kernel addresses in TTBR1. Just set the reserved TTBR0. + */ + if (next == &init_mm) { + cpu_set_reserved_ttbr0(); + return; + } + if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) check_and_switch_context(next, tsk); }