From patchwork Tue Feb 18 18:25:35 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Auger X-Patchwork-Id: 13980454 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 49594C021AA for ; Tue, 18 Feb 2025 18:29:19 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tkSKw-0006di-PM; Tue, 18 Feb 2025 13:28:52 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tkSKX-0006Rj-Pi for qemu-devel@nongnu.org; Tue, 18 Feb 2025 13:28:27 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tkSKW-0008UT-8c for qemu-devel@nongnu.org; Tue, 18 Feb 2025 13:28:25 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739903303; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Hzy1s/cX5PZBqXxEFMKtvC50muZSUNBgdHX/8kzCoeU=; b=dzeJ1c4CzzCLF2c2FSS+GlD11enZlhMMLLmFHglard2v5S7XXn7SP+OmpxbxqF6ApMzXOV VJD8L2ngZFk8R4YZE+Rhg9kg18iEwwTB/PEpCPmmiTTgyuTkMessUSL0ZfiICzMmM5cpo7 aguhTncgXqSHyRDBJvOtTy5uFhD0ppw= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-151-uHDJB473NCyVaaENyFn6Eg-1; Tue, 18 Feb 2025 13:28:18 -0500 X-MC-Unique: uHDJB473NCyVaaENyFn6Eg-1 X-Mimecast-MFC-AGG-ID: uHDJB473NCyVaaENyFn6Eg_1739903295 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2A48019373D9; Tue, 18 Feb 2025 18:28:15 +0000 (UTC) Received: from laptop.redhat.com (unknown [10.45.224.254]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id F1F4A180035F; Tue, 18 Feb 2025 18:28:09 +0000 (UTC) From: Eric Auger To: eric.auger.pro@gmail.com, eric.auger@redhat.com, qemu-devel@nongnu.org, qemu-arm@nongnu.org, peter.maydell@linaro.org, mst@redhat.com, jasowang@redhat.com, imammedo@redhat.com, peterx@redhat.com, alex.williamson@redhat.com, clg@redhat.com, philmd@linaro.org, zhenzhong.duan@intel.com, ddutile@redhat.com Subject: [PATCH v3 5/5] docs/devel/reset: Document reset expectations for DMA and IOMMU Date: Tue, 18 Feb 2025 19:25:35 +0100 Message-ID: <20250218182737.76722-6-eric.auger@redhat.com> In-Reply-To: <20250218182737.76722-1-eric.auger@redhat.com> References: <20250218182737.76722-1-eric.auger@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=eric.auger@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.423, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org To avoid any translation faults, the IOMMUs are expected to be reset after the devices they protect. Document that we expect DMA requests to be stopped during the 'enter' or 'hold' phase while IOMMUs should be reset during the 'exit' phase. Signed-off-by: Eric Auger Reviewed-by: Zhenzhong Duan --- docs/devel/reset.rst | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/docs/devel/reset.rst b/docs/devel/reset.rst index adefd59ef9..0b8b2fa5f4 100644 --- a/docs/devel/reset.rst +++ b/docs/devel/reset.rst @@ -143,6 +143,11 @@ The *exit* phase is executed only when the last reset operation ends. Therefore the object does not need to care how many of reset controllers it has and how many of them have started a reset. +DMA capable devices are expected to cancel all outstanding DMA operations +during either 'enter' or 'hold' phases. IOMMUs are expected to reset during +the 'exit' phase and this sequencing makes sure no outstanding DMA request +will fault. + Handling reset in a resettable object -------------------------------------