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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0CD3FC07E9A for ; Wed, 14 Jul 2021 10:25:57 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 86AE261363 for ; Wed, 14 Jul 2021 10:25:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 86AE261363 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 4BADA414CC; Wed, 14 Jul 2021 10:25:56 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id inn0w1cMtO7J; Wed, 14 Jul 2021 10:25:55 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp4.osuosl.org (Postfix) with ESMTPS id 1AA6840695; Wed, 14 Jul 2021 10:25:55 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id E0236C001A; Wed, 14 Jul 2021 10:25:54 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [IPv6:2605:bc80:3010::136]) by lists.linuxfoundation.org (Postfix) with ESMTP id C15B7C000E for ; Wed, 14 Jul 2021 10:25:53 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id AFDB260A72 for ; Wed, 14 Jul 2021 10:25:53 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id rYIZVzilMvPn for ; Wed, 14 Jul 2021 10:25:53 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from theia.8bytes.org (8bytes.org [81.169.241.247]) by smtp3.osuosl.org (Postfix) with ESMTPS id 16904606CA for ; Wed, 14 Jul 2021 10:25:53 +0000 (UTC) Received: by theia.8bytes.org (Postfix, from userid 1000) id 7006E3D0; Wed, 14 Jul 2021 12:25:47 +0200 (CEST) Date: Wed, 14 Jul 2021 12:25:31 +0200 From: Joerg Roedel To: Konrad Rzeszutek Wilk Subject: Re: [PATCH] iommu/amd: Enable swiotlb if any device supports iommu v2 and uses identity mapping Message-ID: References: <20210708074232.924844-1-kai.heng.feng@canonical.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Cc: will@kernel.org, "open list:AMD IOMMU \(AMD-VI\)" , Kai-Heng Feng , Robin Murphy , open list X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Tue, Jul 13, 2021 at 07:57:40PM -0400, Konrad Rzeszutek Wilk wrote: > The SWIOTLB does have support to do late initialization (xen-pcifront > does that for example - so if you add devices that can't do 64-bit it > will allocate something like 4MB). That sounds like a way to evaluate. I suggest to allocate the SWIOTLB memory at boot and when the IOMMUs are initialized we re-evaluate what we ended up with and free the SWIOTLB memory if its not needed. If that turns out to be wrong during runtime (e.g. because a device is switched to a passthrough default domain at runtime), we allocate a small aperture for this device like the above mentioned 4MB. (A boot option to always keep the aperture around might also be helpful for some setups) Regards, Joerg _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu