From nobody Mon Jun 29 19:37:06 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C659C433EF for ; Fri, 4 Feb 2022 11:55:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358499AbiBDLzm (ORCPT ); Fri, 4 Feb 2022 06:55:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230501AbiBDLzl (ORCPT ); Fri, 4 Feb 2022 06:55:41 -0500 Received: from theia.8bytes.org (8bytes.org [IPv6:2a01:238:4383:600:38bc:a715:4b6d:a889]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53D91C061714 for ; Fri, 4 Feb 2022 03:55:41 -0800 (PST) Received: from cap.home.8bytes.org (p549ad610.dip0.t-ipconnect.de [84.154.214.16]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by theia.8bytes.org (Postfix) with ESMTPSA id 3B50C2F6; Fri, 4 Feb 2022 12:55:39 +0100 (CET) From: Joerg Roedel To: Joerg Roedel Cc: Suravee Suthikulpanit , Will Deacon , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Joerg Roedel Subject: [PATCH v2] iommu/amd: Fix loop timeout issue in iommu_ga_log_enable() Date: Fri, 4 Feb 2022 12:55:37 +0100 Message-Id: <20220204115537.3894-1-joro@8bytes.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Joerg Roedel The polling loop for the register change in iommu_ga_log_enable() needs to have a udelay() in it. Otherwise the CPU might be faster than the IOMMU hardware and wrongly trigger the WARN_ON() further down the code stream. Use a 10us for udelay(), has there is some hardware where activation of the GA log can take more than a 100ms. A future optimization should move the activation check of the GA log to the point where it gets used for the first time. But that is a bigger change and not suitable for a fix. Fixes: 8bda0cfbdc1a ("iommu/amd: Detect and initialize guest vAPIC log") Signed-off-by: Joerg Roedel --- drivers/iommu/amd/init.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c index dc338acf3338..b10fb52ea442 100644 --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -834,6 +835,7 @@ static int iommu_ga_log_enable(struct amd_iommu *iommu) status =3D readl(iommu->mmio_base + MMIO_STATUS_OFFSET); if (status & (MMIO_STATUS_GALOG_RUN_MASK)) break; + udelay(10); } =20 if (WARN_ON(i >=3D LOOP_TIMEOUT)) --=20 2.34.1