From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Wed, 16 Nov 2011 16:48:14 +0000 Subject: [PATCH 4/4] ARM: idmap: use idmap_pgd when setting up mm for reboot In-Reply-To: <1321462094-6647-1-git-send-email-will.deacon@arm.com> References: <1321462094-6647-1-git-send-email-will.deacon@arm.com> Message-ID: <1321462094-6647-5-git-send-email-will.deacon@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org For soft-rebooting a system, it is necessary to map the MMU-off code with an identity mapping so that execution can continue safely once the MMU has been switched off. Currently, switch_mm_for_reboot takes out a 1:1 mapping from 0x0 to TASK_SIZE during reboot in the hope that the reset code lives at a physical address corresponding to a userspace virtual address. This patch modifies the code so that we switch to the idmap_pgd tables, which contain a 1:1 mapping of the cpu_reset code. This has the advantage of only remapping the code that we need and also means we don't need to worry about allocating a pgd from an atomic context in the case that the physical address of the cpu_reset code aliases with the virtual space used by the kernel. Signed-off-by: Will Deacon --- arch/arm/mm/idmap.c | 19 ++++++++++--------- 1 files changed, 10 insertions(+), 9 deletions(-) diff --git a/arch/arm/mm/idmap.c b/arch/arm/mm/idmap.c index 8c1230a..0f96fb2 100644 --- a/arch/arm/mm/idmap.c +++ b/arch/arm/mm/idmap.c @@ -104,17 +104,18 @@ static int __init init_static_idmap(void) arch_initcall(init_static_idmap); /* - * In order to soft-boot, we need to insert a 1:1 mapping in place of - * the user-mode pages. This will then ensure that we have predictable - * results when turning the mmu off + * In order to soft-boot, we need to switch to a 1:1 mapping for the + * cpu_reset functions. This will then ensure that we have predictable + * results when turning off the mmu. */ void setup_mm_for_reboot(char mode) { - /* - * We need to access to user-mode page tables here. For kernel threads - * we don't have any user-mode mappings so we use the context that we - * "borrowed". - */ - identity_mapping_add(current->active_mm->pgd, 0, TASK_SIZE); + /* Clean and invalidate L1. */ + flush_cache_all(); + + /* Switch exclusively to kernel mappings. */ + cpu_switch_mm(idmap_pgd, &init_mm); + + /* Flush the TLB. */ local_flush_tlb_all(); } -- 1.7.4.1