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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 25B42C531D0 for ; Mon, 27 Jul 2026 17:21:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=hnWmUjAH7/KGAbRfo7IseJs1hEL0jSfFDpWwQ2aUfX0=; b=wsl8E5tkuTqf/HUGoa9K/tELoM crafpEdcRkm/QytQZ0sF46c6rx5ulvLwJLGhV+TmLMkahBmnwmdyX2uDqNjhTJRuHdvJBANE+n0Sr 6rPAUrdmirF0jNLdeWEoGkzR1KLgnW44KO0AqxVblGDbQat7mLbQMlzlPQWStSO4blsxCZceBQKxq HrQC+Xa+Ylolp6J4Ib9EM0a5LFrS/E3Hv+EsDi2CifkhVcX+xmCnsB1I/UW2jIZ9zANo5q8KRrGy4 pp/zUJfy7pA98uCJXjoPo0c61BeEwuqM9EGWgEybUEKXS9/ST6Pl5yGgKv5mCOLH5hwm/snNxcz1F r+U1GdYA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1woOKr-00000003OQS-0UiX; Mon, 27 Jul 2026 16:37:49 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1woOJL-00000003NcB-3mzP for linux-arm-kernel@bombadil.infradead.org; Mon, 27 Jul 2026 16:36:15 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:MIME-Version :References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=hnWmUjAH7/KGAbRfo7IseJs1hEL0jSfFDpWwQ2aUfX0=; b=VLp5tvSHY2ORUwGBPzgfAGk2Cc CxNHYbbFn8c9nZADtx9d93qY9KB0tn9O/7HmnsX0Ph8xhAnaUeAQYZRM4nR7wc6SC+U0xl4IABzfb 9iz3EzV8iI+3b0ZR2GccwJ2uqREg24x6wTPDlWLsspPIxm8JpIBulrPPgpOaejD9bnVYb8jsK+XTU eAshSX1ls2rUTSiReny/c7CijDk6lUtP9bOsEFNkO2+M+wFHMLYhfekvbQ1059rhQUgfWOdHNMi/n 6Xai9CQjnXIXA4ikK8lGYyGCsOt3+vcDQJ2FIwuqxGJZUpfswe4KdXP2t6aH/+V1QID+NRtVEbumy WiwfPYIw==; Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.99.2 #2 (Red Hat Linux)) id 1woOJH-00000004GvD-0hZZ for linux-arm-kernel@lists.infradead.org; Mon, 27 Jul 2026 16:36:14 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AA7331688; Mon, 27 Jul 2026 09:36:04 -0700 (PDT) Received: from login2.euhpc2.arm.com (login2.euhpc2.arm.com [10.58.100.22]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D3EDA3F86F; Mon, 27 Jul 2026 09:36:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785170168; bh=dt6wjM09wo8MAqKwtPP6BsZ2ym3CeAlNJuq/rRoZ6O0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pyVuq0sXufwq6pxldnGmOFwX5qo8AXhsCvlwm5vga4q75ntwKvakGJ6HxxlKUqsh1 qev8VUGI4AYLMaJi9ppVXU/Wv2P/GHdldGgazLFgpKEW9ttI7hfpHI0+6/DFBJrY9J lOamITeYZfSrHcMSdvkDRBwc2DQa7FzMp6QLBn7w= From: Vladimir Murzin To: linux-arm-kernel@lists.infradead.org Cc: mark.rutland@arm.com, maz@kernel.org, will@kernel.org, catalin.marinas@arm.com, ruanjinjie@huawei.com, liaochang1@huawei.com Subject: [RFC PATCH v2 39/45] arm64: smp: Fall back to IRQ when IPI NMI request fails Date: Mon, 27 Jul 2026 17:34:47 +0100 Message-Id: <20260727163453.7969-40-vladimir.murzin@arm.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20260727163453.7969-1-vladimir.murzin@arm.com> References: <20260727163453.7969-1-vladimir.murzin@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260727_173611_542985_74D85590 X-CRM114-Status: GOOD ( 16.10 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Existing IPI setup logic relies on ipi_should_be_nmi() to decide whether to request an NMI (if supported) or an ordinary IRQ. If NMI is not supported, using an ordinary IRQ is acceptable. FEAT_NMI requires complementary support in the interrupt controller. If FEAT_NMI is present but interrupt controller support is absent, request_percpu_nmi() can fail. One way to prevent this would be to extend ipi_should_be_nmi() to also check for interrupt controller support. However, since falling back to an ordinary IRQ is acceptable, treat ipi_should_be_nmi() as a hint instead. Whether an IPI is actually registered as an NMI is determined by the success or failure of request_percpu_nmi(). If the request fails, fall back to request_irq(). Track which IPIs were actually registered as NMIs and use that state in the per-CPU enable and disable paths. This avoids calling the percpu NMI helpers for an IPI that fell back to regular IRQ handling. Signed-off-by: Vladimir Murzin --- arch/arm64/kernel/smp.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 3dd4bc02caed..9bacdbb2aa44 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -69,11 +69,13 @@ static int nr_ipi __ro_after_init = NR_IPI; struct ipi_descs { struct irq_desc *descs[MAX_IPI]; + DECLARE_BITMAP(nmi_bitmap, MAX_IPI); }; static DEFINE_PER_CPU_READ_MOSTLY(struct ipi_descs, pcpu_ipi_desc); #define get_ipi_desc(__cpu, __ipi) (per_cpu_ptr(&pcpu_ipi_desc, __cpu)->descs[__ipi]) +#define get_ipi_nmi_bitmap(__cpu) (per_cpu_ptr(&pcpu_ipi_desc, __cpu)->nmi_bitmap) struct ipi_irq_ops { void (*setup)(int ipi, int ncpus); @@ -1051,31 +1053,44 @@ static bool ipi_should_be_nmi(enum ipi_msg_type ipi) static void ipi_sgi_setup(int ipi, int ncpus) { + bool is_nmi = ipi_should_be_nmi(ipi); int err, irq, cpu; if (WARN_ON_ONCE(ncpus)) return; - irq = ipi_irq_base + ipi; - if (ipi_should_be_nmi(ipi)) { - err = request_percpu_nmi(irq, ipi_handler, "IPI", NULL, &irq_stat); - WARN(err, "Could not request IRQ %d as NMI, err=%d\n", irq, err); - } else { + /* + * Try to request NMI if it should be + */ + if (is_nmi && request_percpu_nmi(irq, ipi_handler, "IPI", NULL, &irq_stat)) { + /* + * Fallback to regular IRQ + */ + is_nmi = false; + } + + /* + * Otherwise regular IRQ + */ + if (!is_nmi) { err = request_percpu_irq(irq, ipi_handler, "IPI", &irq_stat); WARN(err, "Could not request IRQ %d as IRQ, err=%d\n", irq, err); } - for_each_possible_cpu(cpu) + for_each_possible_cpu(cpu) { get_ipi_desc(cpu, ipi) = irq_to_desc(irq); + if (is_nmi) + set_bit(ipi, get_ipi_nmi_bitmap(cpu)); + } irq_set_status_flags(irq, IRQ_HIDDEN); } static void ipi_sgi_enable(int cpu, int ipi) { - if (ipi_should_be_nmi(ipi)) { + if (test_bit(ipi, get_ipi_nmi_bitmap(cpu))) { prepare_percpu_nmi(ipi_irq_base + ipi); enable_percpu_nmi(ipi_irq_base + ipi, 0); } else { @@ -1085,7 +1100,7 @@ static void ipi_sgi_enable(int cpu, int ipi) static void ipi_sgi_disable(int cpu, int ipi) { - if (ipi_should_be_nmi(ipi)) { + if (test_bit(ipi, get_ipi_nmi_bitmap(cpu))) { disable_percpu_nmi(ipi_irq_base + ipi); teardown_percpu_nmi(ipi_irq_base + ipi); } else { -- 2.34.1