From mboxrd@z Thu Jan 1 00:00:00 1970 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=-20.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 D59DDC28CFB for ; Tue, 2 Mar 2021 10:11:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BE3346146D for ; Tue, 2 Mar 2021 10:11:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379897AbhCBKGT (ORCPT ); Tue, 2 Mar 2021 05:06:19 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:36100 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1577832AbhCBJ4Q (ORCPT ); Tue, 2 Mar 2021 04:56:16 -0500 Date: Tue, 02 Mar 2021 09:54:48 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1614678888; h=from:from:sender:sender:reply-to: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: in-reply-to:in-reply-to:references:references; bh=49p7cA7i8tse/kWOKzTPD7pxrB3gUqx0zwBBz6irmA4=; b=cuB5L2nK8i90W6GGH+L1tmLnohk+9TL+sf/uXBEzL0mzpiUniFwRqIidsTINufoQQmiztn bxd8CCw3EBJ1vIX6nDAC7Bo9pelUD43PvamuUxGbxc4JUPC4mViBUIHSEO+1eVeGM5EaCf yUdFWRZ+ZLyNRTAVQq84BgQ7fSBk0yi0BVAPESAJCRvQtWTykdbfrvXyQbYzt7YNXftjNG 3O8Cw2wboGv2x5Pk8qqaDSVd/hedp3jDHmKZN6taXY4b4iVAyfimvE3XOkYdPgo75GmkD4 oY9sOQRgRgfshiUYd7j1kHLvMYSybHrBWC0XJ6DD6dWVQSk0+yYV9RGkpHRaeA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1614678888; h=from:from:sender:sender:reply-to: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: in-reply-to:in-reply-to:references:references; bh=49p7cA7i8tse/kWOKzTPD7pxrB3gUqx0zwBBz6irmA4=; b=qI63oQEfcMb8eSFdqh1NK+FPTfzpvpHsffwnmSMGoFzUN7NfRkecAZJGKJbbGGY5vs4vrp eDxd/DmYu6ovB1DQ== From: "tip-bot2 for Nadav Amit" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/mm] x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy() Cc: Nadav Amit , Ingo Molnar , Dave Hansen , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210220231712.2475218-4-namit@vmware.com> References: <20210220231712.2475218-4-namit@vmware.com> MIME-Version: 1.0 Message-ID: <161467888821.20312.12386170191227269746.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/mm branch of tip: Commit-ID: bc51e8e6f9c387d8dda1d8dea2b8856d0ade4101 Gitweb: https://git.kernel.org/tip/bc51e8e6f9c387d8dda1d8dea2b8856d0ade4101 Author: Nadav Amit AuthorDate: Sat, 20 Feb 2021 15:17:06 -08:00 Committer: Ingo Molnar CommitterDate: Tue, 02 Mar 2021 08:01:37 +01:00 x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy() Open-code on_each_cpu_cond_mask() in native_flush_tlb_others() to optimize the code. Open-coding eliminates the need for the indirect branch that is used to call is_lazy(), and in CPUs that are vulnerable to Spectre v2, it eliminates the retpoline. In addition, it allows to use a preallocated cpumask to compute the CPUs that should be. This would later allow us not to adapt on_each_cpu_cond_mask() to support local and remote functions. Note that calling tlb_is_not_lazy() for every CPU that needs to be flushed, as done in native_flush_tlb_multi() might look ugly, but it is equivalent to what is currently done in on_each_cpu_cond_mask(). Actually, native_flush_tlb_multi() does it more efficiently since it avoids using an indirect branch for the matter. Signed-off-by: Nadav Amit Signed-off-by: Ingo Molnar Reviewed-by: Dave Hansen Link: https://lore.kernel.org/r/20210220231712.2475218-4-namit@vmware.com --- arch/x86/mm/tlb.c | 37 ++++++++++++++++++++++++++++++++----- 1 file changed, 32 insertions(+), 5 deletions(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index bf12371..07b6701 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -788,11 +788,13 @@ done: nr_invalidate); } -static bool tlb_is_not_lazy(int cpu, void *data) +static bool tlb_is_not_lazy(int cpu) { return !per_cpu(cpu_tlbstate.is_lazy, cpu); } +static DEFINE_PER_CPU(cpumask_t, flush_tlb_mask); + STATIC_NOPV void native_flush_tlb_others(const struct cpumask *cpumask, const struct flush_tlb_info *info) { @@ -813,12 +815,37 @@ STATIC_NOPV void native_flush_tlb_others(const struct cpumask *cpumask, * up on the new contents of what used to be page tables, while * doing a speculative memory access. */ - if (info->freed_tables) + if (info->freed_tables) { smp_call_function_many(cpumask, flush_tlb_func, (void *)info, 1); - else - on_each_cpu_cond_mask(tlb_is_not_lazy, flush_tlb_func, - (void *)info, 1, cpumask); + } else { + /* + * Although we could have used on_each_cpu_cond_mask(), + * open-coding it has performance advantages, as it eliminates + * the need for indirect calls or retpolines. In addition, it + * allows to use a designated cpumask for evaluating the + * condition, instead of allocating one. + * + * This code works under the assumption that there are no nested + * TLB flushes, an assumption that is already made in + * flush_tlb_mm_range(). + * + * cond_cpumask is logically a stack-local variable, but it is + * more efficient to have it off the stack and not to allocate + * it on demand. Preemption is disabled and this code is + * non-reentrant. + */ + struct cpumask *cond_cpumask = this_cpu_ptr(&flush_tlb_mask); + int cpu; + + cpumask_clear(cond_cpumask); + + for_each_cpu(cpu, cpumask) { + if (tlb_is_not_lazy(cpu)) + __cpumask_set_cpu(cpu, cond_cpumask); + } + smp_call_function_many(cond_cpumask, flush_tlb_func, (void *)info, 1); + } } void flush_tlb_others(const struct cpumask *cpumask,