From patchwork Fri Dec 18 17:01:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 345533 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A400C2BBD5 for ; Fri, 18 Dec 2020 17:04:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E60C23B74 for ; Fri, 18 Dec 2020 17:04:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732190AbgLRREA (ORCPT ); Fri, 18 Dec 2020 12:04:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:54336 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725797AbgLRRD7 (ORCPT ); Fri, 18 Dec 2020 12:03:59 -0500 From: Ard Biesheuvel Authentication-Results: mail.kernel.org; dkim=permerror (bad message/signature format) To: linux-crypto@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Ard Biesheuvel , Dave Martin , Mark Brown , Herbert Xu , Eric Biggers , Will Deacon , Catalin Marinas , Thomas Gleixner , Peter Zijlstra , Sebastian Andrzej Siewior , Ingo Molnar Subject: [RFC PATCH 4/5] arm64: fpsimd: run kernel mode NEON with softirqs disabled Date: Fri, 18 Dec 2020 18:01:05 +0100 Message-Id: <20201218170106.23280-5-ardb@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20201218170106.23280-1-ardb@kernel.org> References: <20201218170106.23280-1-ardb@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org Kernel mode NEON can be used in task or softirq context, but only in a non-nesting manner, i.e., softirq context is only permitted if the interrupt was not taken at a point where the kernel was using the NEON in task context. This means all users of kernel mode NEON have to be aware of this limitation, and either need to provide scalar fallbacks that may be much slower (up to 20x for AES instructions) and potentially less safe, or use an asynchronous interface that defers processing to a later time when the NEON is guaranteed to be available. Given that grabbing and releasing the NEON is cheap, we can relax this restriction, by increasing the granularity of kernel mode NEON code, and always disabling softirq processing while the NEON is being used in task context. Signed-off-by: Ard Biesheuvel --- arch/arm64/include/asm/assembler.h | 19 +++++++++++++------ arch/arm64/kernel/asm-offsets.c | 2 ++ arch/arm64/kernel/fpsimd.c | 4 ++-- 3 files changed, 17 insertions(+), 8 deletions(-) diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index ddbe6bf00e33..74ce46ed55ac 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -15,6 +15,7 @@ #include #include +#include #include #include #include @@ -717,17 +718,23 @@ USER(\label, ic ivau, \tmp2) // invalidate I line PoU .endm .macro if_will_cond_yield_neon -#ifdef CONFIG_PREEMPTION get_current_task x0 ldr x0, [x0, #TSK_TI_PREEMPT] - sub x0, x0, #PREEMPT_DISABLE_OFFSET - cbz x0, .Lyield_\@ +#ifdef CONFIG_PREEMPTION + cmp x0, #PREEMPT_DISABLE_OFFSET + beq .Lyield_\@ // yield on need_resched in task context +#endif + /* never yield while serving a softirq */ + tbnz x0, #SOFTIRQ_SHIFT, .Lnoyield_\@ + + adr_l x0, irq_stat + IRQ_CPUSTAT_SOFTIRQ_PENDING + this_cpu_offset x1 + ldr w0, [x0, x1] + cbnz w0, .Lyield_\@ // yield on pending softirq in task context +.Lnoyield_\@: /* fall through to endif_yield_neon */ .subsection 1 .Lyield_\@ : -#else - .section ".discard.cond_yield_neon", "ax" -#endif .endm .macro do_cond_yield_neon diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 7d32fc959b1a..34ef70877de4 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -93,6 +93,8 @@ int main(void) DEFINE(DMA_FROM_DEVICE, DMA_FROM_DEVICE); BLANK(); DEFINE(PREEMPT_DISABLE_OFFSET, PREEMPT_DISABLE_OFFSET); + DEFINE(SOFTIRQ_SHIFT, SOFTIRQ_SHIFT); + DEFINE(IRQ_CPUSTAT_SOFTIRQ_PENDING, offsetof(irq_cpustat_t, __softirq_pending)); BLANK(); DEFINE(CPU_BOOT_STACK, offsetof(struct secondary_data, stack)); DEFINE(CPU_BOOT_TASK, offsetof(struct secondary_data, task)); diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 062b21f30f94..823e3a8a8871 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -180,7 +180,7 @@ static void __get_cpu_fpsimd_context(void) */ static void get_cpu_fpsimd_context(void) { - preempt_disable(); + local_bh_disable(); __get_cpu_fpsimd_context(); } @@ -201,7 +201,7 @@ static void __put_cpu_fpsimd_context(void) static void put_cpu_fpsimd_context(void) { __put_cpu_fpsimd_context(); - preempt_enable(); + local_bh_enable(); } static bool have_cpu_fpsimd_context(void)