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 F1DB1C76195 for ; Tue, 28 Mar 2023 11:57:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=2GLmIkMvhjz2M+qfS7LdOaG5nPy/EOD2F52lFVjiTUk=; b=21jx+WPd1U8TAx AjS2QV66wvOqKiB+I6Lprv0R4lO5HqQNqK8kmI/L9Dcthh0PoCltdSRYbZ06K2aJd0oT18JsTBvUV jnNCOU7j5C2JBMxEXDjFUOjM0QakDL+95yRfPwRZ2EBIizW79BBxKTQYV/htP0yr+xNImft0BXPkR hbe+P5TOKU6aB9D4+WUU9C3zx2nqLty5wxL6k3K0r6mVK41r1ImMdhEFYyp6D9oePO18mlUvpjplG 9xjfHWFDHGA93NZZt4w3w7qZzuxD2JrnSHPA9TfOHAsCe/btkZhI6Z0OKHUCagg51zlrPXrtr1Us8 KsIWo0SzPKvORdN4USYA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1ph7w8-00EFQd-19; Tue, 28 Mar 2023 11:56:24 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1ph7w5-00EFP3-1I for linux-arm-kernel@lists.infradead.org; Tue, 28 Mar 2023 11:56:22 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E56F0B81C1F; Tue, 28 Mar 2023 11:56:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33C3BC4339C; Tue, 28 Mar 2023 11:56:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1680004578; bh=U2DW5wR8I1ZnOjNwxXw2mRrvf2AHqGXqR88pB/8UTYU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dTwWYfZU4J2Ib3dwZ3Njl4iJAtPe6BdRRvfxDIXxOCIDjXfGboRrRwg/4MECJZ9dq S4njcNJePJLjHlIaEqKd9aEN+Y4yAKvxfiMZxB1nMurJuT7a8R3wghHhWebHrsO2cV 35MoaiM2qKybmShAHRDXSOg79kbRJ2ee4Mc0tnYVtL7OErOHu8J7ZRHskbpkaWYBbp N//kqpY4lYkPV1qApP1eHmGGesgiJ2vhwHDBfONhRGM4bIlP0AVtMrL33rtsO7gmR1 mV/IuGla5NpHQGnqICuA0edO+WU9g5RDQG3t8x88VbNc/v4f4fBaC2FVIK80yoMRWg vMrClSn5jmncw== Date: Tue, 28 Mar 2023 12:56:13 +0100 From: Will Deacon To: "Krcka, Tomas" Cc: "linux-arm-kernel@lists.infradead.org" , Robin Murphy , Joerg Roedel , Lu Baolu , Shameer Kolothum , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] iommu/arm-smmu-v3: Fix event queue overflow acknowledgment Message-ID: <20230328115613.GB1159@willie-the-truck> References: <20230308092048.71390-1-krckatom@amazon.de> <20230327121234.GA31342@willie-the-truck> <8845FA6A-45F1-4090-B4A2-C0C28F709095@amazon.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <8845FA6A-45F1-4090-B4A2-C0C28F709095@amazon.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230328_045621_759046_6A00C4D1 X-CRM114-Status: GOOD ( 27.56 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Mar 28, 2023 at 07:13:52AM +0000, Krcka, Tomas wrote: > > > On 27. Mar 2023, at 14:12, Will Deacon wrote: > > > > > > On Wed, Mar 08, 2023 at 09:20:47AM +0000, Tomas Krcka wrote: > >> When an overflow occurs in the event queue, the SMMU toggles overflow > >> flag OVFLG in the PROD register. > >> The evtq thread is supposed to acknowledge the overflow flag by toggling > >> flag OVACKFLG in the CONS register, otherwise the overflow condition is > >> still active (OVFLG != OVACKFLG). > >> > >> Currently the acknowledge register is toggled after clearing the event > >> queue but is never propagated to the hardware. It would be done next > >> time when executing evtq thread. > >> > >> The SMMU still adds elements to the queue when the overflow condition is > >> active but any subsequent overflow information after clearing the event > >> queue will be lost. > >> > >> This change keeps the SMMU in sync as it's expected by design. > >> > >> Signed-off-by: Tomas Krcka > >> Suggested-by: KarimAllah Ahmed > >> --- > >> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 1 + > >> 1 file changed, 1 insertion(+) > >> > >> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >> index f2425b0f0cd6..acc1ff5ff69b 100644 > >> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >> @@ -1579,6 +1579,7 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev) > >> /* Sync our overflow flag, as we believe we're up to speed */ > >> llq->cons = Q_OVF(llq->prod) | Q_WRP(llq, llq->cons) | > >> Q_IDX(llq, llq->cons); > >> + queue_sync_cons_out(q); > >> return IRQ_HANDLED; > >> } > > > > I think I probably did mean to have something like this, but can we > > only do the actual h/w update if overflow has occurred? Otherwise I think > > we're pointlessly writing back the same value most of the time. > > > > Will > > Yes, we can, but then same applies for the priq as well, there we also write back > every time. Sure, feel free to update both. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel