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 E63FEC3DA6D for ; Tue, 20 May 2025 11:38:32 +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:In-Reply-To: Content-Transfer-Encoding:Content-Type: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=NgeWJFfmKnkx38wotSribUePaK3CDU4bfnUyr/HuMuM=; b=3uqNfjwjKcyeVu99kKlbwIxSWw rYJ5e3c61Rp8pJu5oCIsUX3z1ylU8AleiXfxMD4cTweGMXTUaKcQRuTcenHZu966KrwAADnQC5tVJ ybNeJHSqdwxzQyHQJc1TB2aRuolxyyGU3cUmIXdk2NSBLuiYTUbb1TLRnU9gpnEvYBSrUYjkhKcOG 28jU9KJ4jOyNf6zOs6sdaX3tOtTxjYqPgvG9JBr5V2fKe/0BU7Weab99h1fdvZhPtIdFt/DnePEAH zYpYRpvMADoszqk/NjdwUgcUrmNB53cH3JvSeXerkeh0F2jUgqQAPhdTl9m816X0leLcr1XxAw8tA AluCD6jg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uHLIe-0000000Cfhk-1Ft1; Tue, 20 May 2025 11:38:24 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uHLCM-0000000CedV-0A5j for linux-arm-kernel@lists.infradead.org; Tue, 20 May 2025 11:31:55 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 483AF5C4A0E; Tue, 20 May 2025 11:29:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9268CC4CEEB; Tue, 20 May 2025 11:31:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747740713; bh=CvDybhlQLGgsaauWyvnvy0fUfy35kQUTWzKrr9rQm+w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ofdYLbVw9naWOMB+EzGo9kBZvwW4kLEAFulhRj7U1+SNOP7XzubmjaDjq3xXD81HE asVMbkGWrhZ02beHdrEgtHSSE9HSvsdrEJbtnnivmJKg77MuwnIMOFtxW0CgeSVNmf EqKNtxziB0IwrCIK/8elCyKsALdB9DCl+ciWml5O6Uh2Dm1ucCGNJVn2++eMOpAQLr yJeOi8layAs/ZP0wKWsmnlJiJS9PTXienZtRWaYPw2Whbu1eOKsSbLKLE69kPDiTZi DBZexSPA57nr7OzlVuH3WE/qc0XzVc3H6bg35HEBDqxL3dGvQ+qZhssW/A47l2JlYh DhtXNITYVLfkw== Date: Tue, 20 May 2025 12:31:47 +0100 From: Will Deacon To: Rob Clark Cc: dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, Connor Abbott , Rob Clark , Robin Murphy , Joerg Roedel , Jason Gunthorpe , Nicolin Chen , Kevin Tian , Joao Martins , "moderated list:ARM SMMU DRIVERS" , "open list:IOMMU SUBSYSTEM" , open list Subject: Re: [PATCH v4 05/40] iommu/io-pgtable-arm: Add quirk to quiet WARN_ON() Message-ID: <20250520113146.GA18435@willie-the-truck> References: <20250514175527.42488-1-robdclark@gmail.com> <20250514175527.42488-6-robdclark@gmail.com> <20250515143309.GA12165@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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-20250520_043154_170271_17A4F018 X-CRM114-Status: GOOD ( 31.87 ) 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 On Thu, May 15, 2025 at 07:48:39AM -0700, Rob Clark wrote: > On Thu, May 15, 2025 at 7:33 AM Will Deacon wrote: > > > > On Wed, May 14, 2025 at 10:53:19AM -0700, Rob Clark wrote: > > > From: Rob Clark > > > > > > In situations where mapping/unmapping sequence can be controlled by > > > userspace, attempting to map over a region that has not yet been > > > unmapped is an error. But not something that should spam dmesg. > > > > > > Now that there is a quirk, we can also drop the selftest_running > > > flag, and use the quirk instead for selftests. > > > > > > Signed-off-by: Rob Clark > > > Acked-by: Robin Murphy > > > Signed-off-by: Rob Clark > > > --- > > > drivers/iommu/io-pgtable-arm.c | 27 ++++++++++++++------------- > > > include/linux/io-pgtable.h | 8 ++++++++ > > > 2 files changed, 22 insertions(+), 13 deletions(-) > > > > [...] > > > > > diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h > > > index bba2a51c87d2..639b8f4fb87d 100644 > > > --- a/include/linux/io-pgtable.h > > > +++ b/include/linux/io-pgtable.h > > > @@ -88,6 +88,13 @@ struct io_pgtable_cfg { > > > * > > > * IO_PGTABLE_QUIRK_ARM_HD: Enables dirty tracking in stage 1 pagetable. > > > * IO_PGTABLE_QUIRK_ARM_S2FWB: Use the FWB format for the MemAttrs bits > > > + * > > > + * IO_PGTABLE_QUIRK_NO_WARN_ON: Do not WARN_ON() on conflicting > > > + * mappings, but silently return -EEXISTS. Normally an attempt > > > + * to map over an existing mapping would indicate some sort of > > > + * kernel bug, which would justify the WARN_ON(). But for GPU > > > + * drivers, this could be under control of userspace. Which > > > + * deserves an error return, but not to spam dmesg. > > > */ > > > #define IO_PGTABLE_QUIRK_ARM_NS BIT(0) > > > #define IO_PGTABLE_QUIRK_NO_PERMS BIT(1) > > > @@ -97,6 +104,7 @@ struct io_pgtable_cfg { > > > #define IO_PGTABLE_QUIRK_ARM_OUTER_WBWA BIT(6) > > > #define IO_PGTABLE_QUIRK_ARM_HD BIT(7) > > > #define IO_PGTABLE_QUIRK_ARM_S2FWB BIT(8) > > > + #define IO_PGTABLE_QUIRK_NO_WARN_ON BIT(9) > > > > This feels a bit fragile to me: > > * IOMMU-API users of io-pgtable shouldn't be passing this quirk > > but might end up doing so to paper over driver bugs. > > > > * Low-level users of io-pgtable who expose page-table operations to > > userspace need to pass the quirk, but might well not bother because > > well-behaved userspace doesn't trigger the warning. > > > > So overall, it's all a bit unsatisfactory. Is there a way we could have > > the warnings only when invoked via the IOMMU API? > > iommu drivers _not_ setting this flag seems like a good way to achieve that ;-) > > The alternative is to move the warns to the iommu driver... but they > could just as easily remove the WARN_ON()s as they could set the > NO_WARN_ON quirk, so :shrug:? Bah, I also don't have a good idea to improve this, so I guess I'll take what you have for now. Will