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=-16.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 4FF91C433B4 for ; Wed, 5 May 2021 16:33:18 +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 F07AD6144C for ; Wed, 5 May 2021 16:33:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F07AD6144C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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 C2BB440630; Wed, 5 May 2021 16:33:17 +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 HFuckfUuwncZ; Wed, 5 May 2021 16:33:16 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp4.osuosl.org (Postfix) with ESMTP id 1775B405C2; Wed, 5 May 2021 16:33:16 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id E47F6C000D; Wed, 5 May 2021 16:33:15 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [IPv6:2605:bc80:3010::136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 21DADC0024 for ; Wed, 5 May 2021 16:33:14 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 02AA360A6E for ; Wed, 5 May 2021 16:33:13 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp3.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=kernel.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 5GrqRoxNaPxj for ; Wed, 5 May 2021 16:33:12 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp3.osuosl.org (Postfix) with ESMTPS id DEF1B60804 for ; Wed, 5 May 2021 16:33:12 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 2867361438; Wed, 5 May 2021 16:33:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1620232392; bh=k7BYsjVDX28HkILI3v2n5y6yPJGjgPrpZVVERGHEIQw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Psk7pdnbLGCQ+Y21vp7rvX6lRB9FMt6nsxnadNr+tixOu2g+SmWhHw+TcTmv8nW87 sxzz569OwgT91PI+VYa0clax+veuhhIsQIEVHoj1yrWEwXh9MWLWSn4JhfMgJ9gbgp CAL6K0ogZMzYSeWH3oHfQ8UTZPfoNgs0y5jIL8WVf2V1PuWjQQnEAmVTz4fxcXv1q4 jVzfycqYoyMQthAf4obcJIpwhfKNzrSHKuYeOkpFRySshGK6DA2pC1wSWJDvrZKHbG jI6YD/wIRVOfu+g5AzkFeYIobzN6GYugnBjcT9egBXNnh1xml/SWIbrzbE7Zwk5N4M RdyxK9UamGbQA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH AUTOSEL 5.12 076/116] iommu/amd: Remove performance counter pre-initialization test Date: Wed, 5 May 2021 12:30:44 -0400 Message-Id: <20210505163125.3460440-76-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210505163125.3460440-1-sashal@kernel.org> References: <20210505163125.3460440-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Cc: Sasha Levin , Paul Menzel , Joerg Roedel , David Coe , Alexander Monakov , iommu@lists.linux-foundation.org, Shuah Khan , Tj 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" From: Suravee Suthikulpanit [ Upstream commit 994d6608efe4a4c8834bdc5014c86f4bc6aceea6 ] In early AMD desktop/mobile platforms (during 2013), when the IOMMU Performance Counter (PMC) support was first introduced in commit 30861ddc9cca ("perf/x86/amd: Add IOMMU Performance Counter resource management"), there was a HW bug where the counters could not be accessed. The result was reading of the counter always return zero. At the time, the suggested workaround was to add a test logic prior to initializing the PMC feature to check if the counters can be programmed and read back the same value. This has been working fine until the more recent desktop/mobile platforms start enabling power gating for the PMC, which prevents access to the counters. This results in the PMC support being disabled unnecesarily. Unfortunatly, there is no documentation of since which generation of hardware the original PMC HW bug was fixed. Although, it was fixed soon after the first introduction of the PMC. Base on this, we assume that the buggy platforms are less likely to be in used, and it should be relatively safe to remove this legacy logic. Link: https://lore.kernel.org/linux-iommu/alpine.LNX.3.20.13.2006030935570.3181@monopod.intra.ispras.ru/ Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201753 Cc: Tj (Elloe Linux) Cc: Shuah Khan Cc: Alexander Monakov Cc: David Coe Cc: Paul Menzel Signed-off-by: Suravee Suthikulpanit Tested-by: Shuah Khan Link: https://lore.kernel.org/r/20210409085848.3908-3-suravee.suthikulpanit@amd.com Signed-off-by: Joerg Roedel Signed-off-by: Sasha Levin --- drivers/iommu/amd/init.c | 24 +----------------------- 1 file changed, 1 insertion(+), 23 deletions(-) diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c index 648cdfd03074..247cdda5d683 100644 --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -1714,33 +1714,16 @@ static int __init init_iommu_all(struct acpi_table_header *table) return 0; } -static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr, - u8 fxn, u64 *value, bool is_write); - static void init_iommu_perf_ctr(struct amd_iommu *iommu) { + u64 val; struct pci_dev *pdev = iommu->dev; - u64 val = 0xabcd, val2 = 0, save_reg = 0; if (!iommu_feature(iommu, FEATURE_PC)) return; amd_iommu_pc_present = true; - /* save the value to restore, if writable */ - if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false)) - goto pc_false; - - /* Check if the performance counters can be written to */ - if ((iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true)) || - (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false)) || - (val != val2)) - goto pc_false; - - /* restore */ - if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true)) - goto pc_false; - pci_info(pdev, "IOMMU performance counters supported\n"); val = readl(iommu->mmio_base + MMIO_CNTR_CONF_OFFSET); @@ -1748,11 +1731,6 @@ static void init_iommu_perf_ctr(struct amd_iommu *iommu) iommu->max_counters = (u8) ((val >> 7) & 0xf); return; - -pc_false: - pci_err(pdev, "Unable to read/write to IOMMU perf counter.\n"); - amd_iommu_pc_present = false; - return; } static ssize_t amd_iommu_show_cap(struct device *dev, -- 2.30.2 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu