From patchwork Thu Oct 29 22:18:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 11867783 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 44500697 for ; Thu, 29 Oct 2020 22:33:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1422E20FC3 for ; Thu, 29 Oct 2020 22:33:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="FOmP5Y2C"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="2P8kK3cK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726192AbgJ2WdL (ORCPT ); Thu, 29 Oct 2020 18:33:11 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:37714 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725861AbgJ2Wch (ORCPT ); Thu, 29 Oct 2020 18:32:37 -0400 Message-Id: <20201029222652.194349374@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1604010748; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=sdXI7uto7JGSNPM0IVUoIg2pbKsluCZDYWtwfegzM8w=; b=FOmP5Y2C/lyOqnO8NRQR7UeX7g96W79J74og5WndG2GjK1T3b2uRiyCBECmKlLcuaXoHu8 bjaO/viBQhQ8bvgNso5sb4fHIkbzpPsCviHoxY+2EsUN1BaZlNmsZcBAmmjBfLppHZ27j1 8lbkSKu8k/8qW6LY2xD1EX5vzaJ3/FdcM9vTyye/Tv7TTKG3aZOv8Jh8oZzsGDDYfH1SQ6 I6rGLBa0cZuLsOHLTT3MjdFH+65ijfrAWHBbcJCQCzQxfFIyFYHpilKwQdNE2o+LoJ/DpZ n2dbzgsWeQRp5mGKz2qckWUEFFHjnxsDDjH0eBmDpexQlEEuO5OoALrI5/Y/gA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1604010748; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=sdXI7uto7JGSNPM0IVUoIg2pbKsluCZDYWtwfegzM8w=; b=2P8kK3cKzIGAVVEcZXJVGmyGsyPoNrPQWyv/xRi4meWRIELqGztBgTX8k0SbykrmKDkQmG lS1o8L5loEELkyBQ== Date: Thu, 29 Oct 2020 23:18:22 +0100 From: Thomas Gleixner To: LKML Cc: linux-arch@vger.kernel.org, Linus Torvalds , Peter Zijlstra , Paul McKenney , David Airlie , Daniel Vetter , Ard Biesheuvel , Herbert Xu , Christoph Hellwig , Sebastian Andrzej Siewior , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Andrew Morton , linux-mm@kvack.org, x86@kernel.org, Vineet Gupta , linux-snps-arc@lists.infradead.org, Russell King , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, Guo Ren , linux-csky@vger.kernel.org, Michal Simek , Thomas Bogendoerfer , linux-mips@vger.kernel.org, Nick Hu , Greentime Hu , Vincent Chen , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, "David S. Miller" , sparclinux@vger.kernel.org, Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org Subject: [patch V2 16/18] sched: highmem: Store local kmaps in task struct References: <20201029221806.189523375@linutronix.de> MIME-Version: 1.0 Content-transfer-encoding: 8-bit Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Instead of storing the map per CPU provide and use per task storage. That prepares for local kmaps which are preemptible. The context switch code is preparatory and not yet in use because kmap_atomic() runs with preemption disabled. Will be made usable in the next step. The context switch logic is safe even when an interrupt happens after clearing or before restoring the kmaps. The kmap index in task struct is not modified so any nesting kmap in an interrupt will use unused indices and on return the counter is the same as before. Also add an assert into the return to user space code. Going back to user space with an active kmap local is a nono. Signed-off-by: Thomas Gleixner --- include/linux/highmem.h | 10 +++++ include/linux/sched.h | 9 ++++ kernel/entry/common.c | 2 + kernel/fork.c | 1 kernel/sched/core.c | 18 +++++++++ mm/highmem.c | 96 +++++++++++++++++++++++++++++++++++++++++------- 6 files changed, 123 insertions(+), 13 deletions(-) --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -38,6 +38,16 @@ static inline void invalidate_kernel_vma void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot); void *__kmap_local_page_prot(struct page *page, pgprot_t prot); void kunmap_local_indexed(void *vaddr); +void kmap_local_fork(struct task_struct *tsk); +void __kmap_local_sched_out(void); +void __kmap_local_sched_in(void); +static inline void kmap_assert_nomap(void) +{ + DEBUG_LOCKS_WARN_ON(current->kmap_ctrl.idx); +} +#else +static inline void kmap_local_fork(struct task_struct *tsk) { } +static inline void kmap_assert_nomap(void) { } #endif #ifdef CONFIG_HIGHMEM --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -34,6 +34,7 @@ #include #include #include +#include /* task_struct member predeclarations (sorted alphabetically): */ struct audit_context; @@ -629,6 +630,13 @@ struct wake_q_node { struct wake_q_node *next; }; +struct kmap_ctrl { +#ifdef CONFIG_KMAP_LOCAL + int idx; + pte_t pteval[KM_TYPE_NR]; +#endif +}; + struct task_struct { #ifdef CONFIG_THREAD_INFO_IN_TASK /* @@ -1294,6 +1302,7 @@ struct task_struct { unsigned int sequential_io; unsigned int sequential_io_avg; #endif + struct kmap_ctrl kmap_ctrl; #ifdef CONFIG_DEBUG_ATOMIC_SLEEP unsigned long task_state_change; #endif --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -2,6 +2,7 @@ #include #include +#include #include #include @@ -194,6 +195,7 @@ static void exit_to_user_mode_prepare(st /* Ensure that the address limit is intact and no locks are held */ addr_limit_user_check(); + kmap_assert_nomap(); lockdep_assert_irqs_disabled(); lockdep_sys_exit(); } --- a/kernel/fork.c +++ b/kernel/fork.c @@ -930,6 +930,7 @@ static struct task_struct *dup_task_stru account_kernel_stack(tsk, 1); kcov_task_init(tsk); + kmap_local_fork(tsk); #ifdef CONFIG_FAULT_INJECTION tsk->fail_nth = 0; --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4053,6 +4053,22 @@ static inline void finish_lock_switch(st # define finish_arch_post_lock_switch() do { } while (0) #endif +static inline void kmap_local_sched_out(void) +{ +#ifdef CONFIG_KMAP_LOCAL + if (unlikely(current->kmap_ctrl.idx)) + __kmap_local_sched_out(); +#endif +} + +static inline void kmap_local_sched_in(void) +{ +#ifdef CONFIG_KMAP_LOCAL + if (unlikely(current->kmap_ctrl.idx)) + __kmap_local_sched_in(); +#endif +} + /** * prepare_task_switch - prepare to switch tasks * @rq: the runqueue preparing to switch @@ -4075,6 +4091,7 @@ prepare_task_switch(struct rq *rq, struc perf_event_task_sched_out(prev, next); rseq_preempt(prev); fire_sched_out_preempt_notifiers(prev, next); + kmap_local_sched_out(); prepare_task(next); prepare_arch_switch(next); } @@ -4141,6 +4158,7 @@ static struct rq *finish_task_switch(str finish_lock_switch(rq); finish_arch_post_lock_switch(); kcov_finish_switch(current); + kmap_local_sched_in(); fire_sched_in_preempt_notifiers(current); /* --- a/mm/highmem.c +++ b/mm/highmem.c @@ -367,27 +367,24 @@ EXPORT_SYMBOL(kunmap_high); #ifdef CONFIG_KMAP_LOCAL -static DEFINE_PER_CPU(int, __kmap_atomic_idx); - -static inline int kmap_atomic_idx_push(void) +static inline int kmap_local_idx_push(void) { - int idx = __this_cpu_inc_return(__kmap_atomic_idx) - 1; + int idx = current->kmap_ctrl.idx++; WARN_ON_ONCE(in_irq() && !irqs_disabled()); BUG_ON(idx >= KM_TYPE_NR); return idx; } -static inline int kmap_atomic_idx(void) +static inline int kmap_local_idx(void) { - return __this_cpu_read(__kmap_atomic_idx) - 1; + return current->kmap_ctrl.idx - 1; } -static inline void kmap_atomic_idx_pop(void) +static inline void kmap_local_idx_pop(void) { - int idx = __this_cpu_dec_return(__kmap_atomic_idx); - - BUG_ON(idx < 0); + current->kmap_ctrl.idx--; + BUG_ON(current->kmap_ctrl.idx < 0); } #ifndef arch_kmap_local_post_map @@ -447,12 +444,13 @@ void *__kmap_local_pfn_prot(unsigned lon int idx; preempt_disable(); - idx = arch_kmap_local_map_idx(kmap_atomic_idx_push(), pfn); + idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn); vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); BUG_ON(!pte_none(*(kmap_pte - idx))); pteval = pfn_pte(pfn, prot); set_pte_at(&init_mm, vaddr, kmap_pte - idx, pteval); arch_kmap_local_post_map(vaddr, pteval); + current->kmap_ctrl.pteval[kmap_local_idx()] = pteval; preempt_enable(); return (void *)vaddr; @@ -491,16 +489,88 @@ void kunmap_local_indexed(void *vaddr) } preempt_disable(); - idx = arch_kmap_local_unmap_idx(kmap_atomic_idx(), addr); + idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr); WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx)); arch_kmap_local_pre_unmap(addr); pte_clear(&init_mm, addr, kmap_pte - idx); arch_kmap_local_post_unmap(addr); - kmap_atomic_idx_pop(); + current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0); + kmap_local_idx_pop(); preempt_enable(); } EXPORT_SYMBOL(kunmap_local_indexed); + +/* + * Invoked before switch_to(). This is safe even when during or after + * clearing the maps an interrupt which needs a kmap_local happens because + * the task::kmap_ctrl.idx is not modified by the unmapping code so a + * nested kmap_local will use the next unused index and restore the index + * on unmap. The already cleared kmaps of the outgoing task are irrelevant + * because the interrupt context does not know about them. The same applies + * when scheduling back in for an interrupt which happens before the + * restore is complete. + */ +void __kmap_local_sched_out(void) +{ + struct task_struct *tsk = current; + pte_t *kmap_pte = kmap_get_pte(); + int i; + + /* Clear kmaps */ + for (i = 0; i < tsk->kmap_ctrl.idx; i++) { + pte_t pteval = tsk->kmap_ctrl.pteval[i]; + unsigned long addr; + int idx; + + if (WARN_ON_ONCE(pte_none(pteval))) + continue; + + /* + * This is a horrible hack for XTENSA to calculate the + * coloured PTE index. Uses the PFN encoded into the pteval + * and the map index calculation because the actual mapped + * virtual address is not stored in task::kmap_ctrl. + * For any sane architecture this is optimized out. + */ + idx = arch_kmap_local_map_idx(i, pte_pfn(pteval)); + + addr = __fix_to_virt(FIX_KMAP_BEGIN + idx); + arch_kmap_local_pre_unmap(addr); + pte_clear(&init_mm, addr, kmap_pte - idx); + arch_kmap_local_post_unmap(addr); + } +} + +void __kmap_local_sched_in(void) +{ + struct task_struct *tsk = current; + pte_t *kmap_pte = kmap_get_pte(); + int i; + + /* Restore kmaps */ + for (i = 0; i < tsk->kmap_ctrl.idx; i++) { + pte_t pteval = tsk->kmap_ctrl.pteval[i]; + unsigned long addr; + int idx; + + if (WARN_ON_ONCE(pte_none(pteval))) + continue; + + /* See comment in __kmap_local_sched_out() */ + idx = arch_kmap_local_map_idx(i, pte_pfn(pteval)); + addr = __fix_to_virt(FIX_KMAP_BEGIN + idx); + set_pte_at(&init_mm, addr, kmap_pte - idx, pteval); + arch_kmap_local_post_map(addr, pteval); + } +} + +void kmap_local_fork(struct task_struct *tsk) +{ + if (WARN_ON_ONCE(tsk->kmap_ctrl.idx)) + memset(&tsk->kmap_ctrl, 0, sizeof(tsk->kmap_ctrl)); +} + #endif #if defined(HASHED_PAGE_VIRTUAL)