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[66.90.148.213]) by smtp.gmail.com with ESMTPSA id i23sm1389213otj.19.2022.02.04.18.14.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Feb 2022 18:14:22 -0800 (PST) Received: (nullmailer pid 3618455 invoked by uid 1000); Sat, 05 Feb 2022 02:14:21 -0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 55fed28c-8629-11ec-8f75-fffcc8bd4f1a X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=bavDyoeix3ivKrmvk1c86k8fQHTEv2BfyXOQ+LGiGnA=; b=MZEBnC6eaqx3T0DUfyoW4fcwcJwoQfbfvqWGLdrUZqfHyzh+FFNKH0o64QYRF0kkO0 sm/04ugnVMQKbhiXBPZBZxbqThDLyoXhvzdbVd04OD8KyiM7cC1rt8jPA+hrKEvIXiFZ 34pXtwM2iZUWBb6LCeaoeeGxDeqPF55vU9r8nO5V+/LYVXTrulY0ZtmHOLFsvfeO66Am k4pxJJ00qarDeA8LB/QhPwpm/hDDcw+oP7N8BvKsqYZDlMsBhj9u0KlgwAk47tr3h0/h R1Nh6hEgZUAf472Dv7HbMkJ8RTxlzVf5f4RoIP6LyikQJDUrRHALYMVb2WnFXn3dgrEy WMtA== X-Gm-Message-State: AOAM532QzaXOOPAPtODdgI4w3e9cpHvJON7PVwbm9IeQgxoU4+xQKvuN 96JWG+BT0T8rZvXDX56a/zXXGEC4Lw== X-Google-Smtp-Source: ABdhPJzohhI86BDByZJvtg/GYgD3FQPT2/j3rlDpD888Vi5x4ag/iD4VE+2Pi/X/ul8DPGRoE3J0Dw== X-Received: by 2002:aca:c056:: with SMTP id q83mr2812199oif.294.1644027263107; Fri, 04 Feb 2022 18:14:23 -0800 (PST) Date: Fri, 4 Feb 2022 20:14:21 -0600 From: Rob Herring To: Stefano Stabellini Cc: Robin Murphy , Sergiy Kibrik , Julien Grall , Oleksandr Tyshchenko , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "xen-devel@lists.xenproject.org" Subject: Re: [PATCH v3 1/2] dt-bindings: arm: xen: document Xen iommu device Message-ID: References: <20220117123251.140867-1-Sergiy_Kibrik@epam.com> <20220117123251.140867-2-Sergiy_Kibrik@epam.com> <447f89ca-86c0-dc35-e7ac-e6639a573670@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Jan 26, 2022 at 10:56:39AM -0800, Stefano Stabellini wrote: > On Wed, 26 Jan 2022, Robin Murphy wrote: > > On 2022-01-26 15:09, Sergiy Kibrik wrote: > > > Hi Robin, > > > > > > > > > > > This could break Linux guests, since depending on the deferred probe > > > > timeout setting it could lead to drivers never probing because the "IOMMU" > > > > never becomes available. > > > > > > > > > > I've noticed no deferred probe timeouts when booting with this patch. Could > > > you please explain more on how this would break guests? > > > > Right now I think it would actually require command-line intervention, e.g. > > "fw_devlink=on" or "deferred_probe_timeout=3600" (with modules enabled for the > > latter to take full effect), but I'm wary of the potential for future config > > options to control those behaviours by default. fw_devlink=on is now the default (for at least a couple of cycles). > > If deferred_probe_timeout=3600 was specified, we would just need an > IOMMU driver in Linux for the "xen,iommu-el2-v1" node to solve the > problem, right? I guess I am trying to say that it wouldn't be a device > tree interface problem but rather a Linux implementation discussion. You would have to add that IOMMU driver to old, existing kernels if you want compatibility with a new DT. Otherwise, that kernel would stop booting with a new DT. Rob 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 CDDC0C433EF for ; Sat, 5 Feb 2022 02:15:49 +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=ckE80B1DDVmvp2oglgoGBI3/Fsxr2gDXGvoJIfndtYg=; b=PXSHG/IMdEQflW FnoJtL+m9pwUGr8wsZ+/BJNtrNcwaO5NujMi1angjUbkkl4AfMR5ngxAycfczAR7SSOx9N0uDc6PE ETumibH7Sx8VvZa6a8DjxxiQrtb5nD1QSHkVgpYKgNBSTcf8uk3PMyGR//UB2qRA8Gh/MxJ+PG7nl 6dZQz/tc4lzPoxXiK5jmTDmRk4dRUmm8GIGRlNSVDl13Zd2LNAMvI+3LQuTIcYOL+4FaeTEiEPDU9 Zogna7w149WvisWg8UOMV6FSHyi6k052jjLCik1LEHxZvCuUDCBXPq4wJBGBjzjzZn/LwUn7UZEJh D4bZZ70+BQskrQRtoYcg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nGAap-005xQ9-BB; Sat, 05 Feb 2022 02:14:27 +0000 Received: from mail-oi1-f171.google.com ([209.85.167.171]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nGAam-005xPc-35 for linux-arm-kernel@lists.infradead.org; Sat, 05 Feb 2022 02:14:25 +0000 Received: by mail-oi1-f171.google.com with SMTP id r27so10657078oiw.4 for ; Fri, 04 Feb 2022 18:14:23 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=bavDyoeix3ivKrmvk1c86k8fQHTEv2BfyXOQ+LGiGnA=; b=LOIj+WxF4i2f2zFapMQDoyjqY3d9JRK2kVo63akQ4k648rbpZViwOcolpGbBjnZDrV 7TUTaB2kXDWEdaABeagXyTY2GlOU8pChM6SSlQVr/U/h+Dlbo8tDVb5rb4yHH3pRa3Fi AS3clFeXlK1ZTumGrpLFlpbJMpx/KYfwV3mESPUhWnC4ByzgSgd/feLeQdZG2UjqRgeC 3dV9Az0yBp3y1FumQ4kRYCTDuaUinh0edldaOFZcf2xW4ABzu9OEdM0Jlc01uKtWI9vI H9LcPV1fN2fr6YDZKu43uLCsd/Ne4iaKfdPUHg792RbpQsCRbX3SSsxHuh4jOGGH57vG 4bng== X-Gm-Message-State: AOAM531HQanSmttdBYr9aZi9N57v1hIysQqJVbYVUpm829xPEqvRzb2S KQZTyut8zrzPG8guJIfjmg== X-Google-Smtp-Source: ABdhPJzohhI86BDByZJvtg/GYgD3FQPT2/j3rlDpD888Vi5x4ag/iD4VE+2Pi/X/ul8DPGRoE3J0Dw== X-Received: by 2002:aca:c056:: with SMTP id q83mr2812199oif.294.1644027263107; Fri, 04 Feb 2022 18:14:23 -0800 (PST) Received: from robh.at.kernel.org (66-90-148-213.dyn.grandenetworks.net. [66.90.148.213]) by smtp.gmail.com with ESMTPSA id i23sm1389213otj.19.2022.02.04.18.14.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Feb 2022 18:14:22 -0800 (PST) Received: (nullmailer pid 3618455 invoked by uid 1000); Sat, 05 Feb 2022 02:14:21 -0000 Date: Fri, 4 Feb 2022 20:14:21 -0600 From: Rob Herring To: Stefano Stabellini Cc: Robin Murphy , Sergiy Kibrik , Julien Grall , Oleksandr Tyshchenko , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "xen-devel@lists.xenproject.org" Subject: Re: [PATCH v3 1/2] dt-bindings: arm: xen: document Xen iommu device Message-ID: References: <20220117123251.140867-1-Sergiy_Kibrik@epam.com> <20220117123251.140867-2-Sergiy_Kibrik@epam.com> <447f89ca-86c0-dc35-e7ac-e6639a573670@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220204_181424_190372_1F9F1C86 X-CRM114-Status: GOOD ( 21.21 ) 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 Wed, Jan 26, 2022 at 10:56:39AM -0800, Stefano Stabellini wrote: > On Wed, 26 Jan 2022, Robin Murphy wrote: > > On 2022-01-26 15:09, Sergiy Kibrik wrote: > > > Hi Robin, > > > > > > > > > > > This could break Linux guests, since depending on the deferred probe > > > > timeout setting it could lead to drivers never probing because the "IOMMU" > > > > never becomes available. > > > > > > > > > > I've noticed no deferred probe timeouts when booting with this patch. Could > > > you please explain more on how this would break guests? > > > > Right now I think it would actually require command-line intervention, e.g. > > "fw_devlink=on" or "deferred_probe_timeout=3600" (with modules enabled for the > > latter to take full effect), but I'm wary of the potential for future config > > options to control those behaviours by default. fw_devlink=on is now the default (for at least a couple of cycles). > > If deferred_probe_timeout=3600 was specified, we would just need an > IOMMU driver in Linux for the "xen,iommu-el2-v1" node to solve the > problem, right? I guess I am trying to say that it wouldn't be a device > tree interface problem but rather a Linux implementation discussion. You would have to add that IOMMU driver to old, existing kernels if you want compatibility with a new DT. Otherwise, that kernel would stop booting with a new DT. Rob _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel