From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7793539FDD; Fri, 24 Nov 2023 18:11:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Anf7VhTn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08487C433C7; Fri, 24 Nov 2023 18:11:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700849496; bh=mWoDm+ymf7VhHM+400ZEP7kKfp+4gQxIXjQqTXeFCsE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Anf7VhTn19EovtspDuUA4fXxD8NQcTlisH8HX3Lk2lULdFBVxdmeObittko7jaDyc P/WYjJfNYJkrz/AetKNnTA02KvMi/pTec3KPiXPSGJTfAKTH70koGwMePGhE0A5y00 M1ybHdNueiZp/AB7dc7IUkiu7KNFGvtmgfTPy39U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Woodhouse , Juergen Gross , Stefano Stabellini , Sasha Levin Subject: [PATCH 6.6 187/530] xen/events: avoid using info_for_irq() in xen_send_IPI_one() Date: Fri, 24 Nov 2023 17:45:53 +0000 Message-ID: <20231124172033.763609383@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231124172028.107505484@linuxfoundation.org> References: <20231124172028.107505484@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Juergen Gross [ Upstream commit e64e7c74b99ec9e439abca75f522f4b98f220bd1 ] xen_send_IPI_one() is being used by cpuhp_report_idle_dead() after it calls rcu_report_dead(), meaning that any RCU usage by xen_send_IPI_one() is a bad idea. Unfortunately xen_send_IPI_one() is using notify_remote_via_irq() today, which is using irq_get_chip_data() via info_for_irq(). And irq_get_chip_data() in turn is using a maple-tree lookup requiring RCU. Avoid this problem by caching the ipi event channels in another percpu variable, allowing the use notify_remote_via_evtchn() in xen_send_IPI_one(). Fixes: 721255b9826b ("genirq: Use a maple tree for interrupt descriptor management") Reported-by: David Woodhouse Signed-off-by: Juergen Gross Tested-by: David Woodhouse Acked-by: Stefano Stabellini Signed-off-by: Juergen Gross Signed-off-by: Sasha Levin --- drivers/xen/events/events_base.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index 1b2136fe0fa51..2cf0c2b693861 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -164,6 +164,8 @@ static DEFINE_PER_CPU(int [NR_VIRQS], virq_to_irq) = {[0 ... NR_VIRQS-1] = -1}; /* IRQ <-> IPI mapping */ static DEFINE_PER_CPU(int [XEN_NR_IPIS], ipi_to_irq) = {[0 ... XEN_NR_IPIS-1] = -1}; +/* Cache for IPI event channels - needed for hot cpu unplug (avoid RCU usage). */ +static DEFINE_PER_CPU(evtchn_port_t [XEN_NR_IPIS], ipi_to_evtchn) = {[0 ... XEN_NR_IPIS-1] = 0}; /* Event channel distribution data */ static atomic_t channels_on_cpu[NR_CPUS]; @@ -366,6 +368,7 @@ static int xen_irq_info_ipi_setup(unsigned cpu, info->u.ipi = ipi; per_cpu(ipi_to_irq, cpu)[ipi] = irq; + per_cpu(ipi_to_evtchn, cpu)[ipi] = evtchn; return xen_irq_info_common_setup(info, irq, IRQT_IPI, evtchn, 0); } @@ -981,6 +984,7 @@ static void __unbind_from_irq(unsigned int irq) break; case IRQT_IPI: per_cpu(ipi_to_irq, cpu)[ipi_from_irq(irq)] = -1; + per_cpu(ipi_to_evtchn, cpu)[ipi_from_irq(irq)] = 0; break; case IRQT_EVTCHN: dev = info->u.interdomain; @@ -1631,7 +1635,7 @@ EXPORT_SYMBOL_GPL(evtchn_put); void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector) { - int irq; + evtchn_port_t evtchn; #ifdef CONFIG_X86 if (unlikely(vector == XEN_NMI_VECTOR)) { @@ -1642,9 +1646,9 @@ void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector) return; } #endif - irq = per_cpu(ipi_to_irq, cpu)[vector]; - BUG_ON(irq < 0); - notify_remote_via_irq(irq); + evtchn = per_cpu(ipi_to_evtchn, cpu)[vector]; + BUG_ON(evtchn == 0); + notify_remote_via_evtchn(evtchn); } struct evtchn_loop_ctrl { -- 2.42.0