From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754714AbeDIUHm (ORCPT ); Mon, 9 Apr 2018 16:07:42 -0400 Received: from mail-wr0-f193.google.com ([209.85.128.193]:46342 "EHLO mail-wr0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754664AbeDIUHh (ORCPT ); Mon, 9 Apr 2018 16:07:37 -0400 X-Google-Smtp-Source: AIpwx48uw1dF3Ku9krx/LUm/VUvwglcUnxgqUNirovinsq4sCXNbXm/JOlHfcu0tAys4xgzEV6afLQ== From: Dmitry Osipenko To: Thierry Reding , Jonathan Hunter , Joerg Roedel Cc: iommu@lists.linux-foundation.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v1 1/4] iommu/tegra: gart: Add debugging facility Date: Mon, 9 Apr 2018 23:07:19 +0300 Message-Id: X-Mailer: git-send-email 2.16.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Page mapping could overwritten by an accident (a bug). We can catch this case by checking 'VALID' bit of GART's page entry prior to mapping of a page. Since that check introduces a small performance impact, it should be enabled explicitly using new GART's kernel module 'debug' parameter. Signed-off-by: Dmitry Osipenko --- drivers/iommu/tegra-gart.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/drivers/iommu/tegra-gart.c b/drivers/iommu/tegra-gart.c index b62f790ad1ba..4c0abdcd1ad2 100644 --- a/drivers/iommu/tegra-gart.c +++ b/drivers/iommu/tegra-gart.c @@ -72,6 +72,8 @@ struct gart_domain { static struct gart_device *gart_handle; /* unique for a system */ +static bool gart_debug; + #define GART_PTE(_pfn) \ (GART_ENTRY_PHYS_ADDR_VALID | ((_pfn) << PAGE_SHIFT)) @@ -271,6 +273,7 @@ static int gart_iommu_map(struct iommu_domain *domain, unsigned long iova, struct gart_device *gart = gart_domain->gart; unsigned long flags; unsigned long pfn; + unsigned long pte; if (!gart_iova_range_valid(gart, iova, bytes)) return -EINVAL; @@ -282,6 +285,14 @@ static int gart_iommu_map(struct iommu_domain *domain, unsigned long iova, spin_unlock_irqrestore(&gart->pte_lock, flags); return -EINVAL; } + if (gart_debug) { + pte = gart_read_pte(gart, iova); + if (pte & GART_ENTRY_PHYS_ADDR_VALID) { + spin_unlock_irqrestore(&gart->pte_lock, flags); + dev_err(gart->dev, "Page entry is in-use\n"); + return -EBUSY; + } + } gart_set_pte(gart, iova, GART_PTE(pfn)); FLUSH_GART_REGS(gart); spin_unlock_irqrestore(&gart->pte_lock, flags); @@ -515,7 +526,9 @@ static void __exit tegra_gart_exit(void) subsys_initcall(tegra_gart_init); module_exit(tegra_gart_exit); +module_param(gart_debug, bool, 0644); +MODULE_PARM_DESC(gart_debug, "Enable GART debugging"); MODULE_DESCRIPTION("IOMMU API for GART in Tegra20"); MODULE_AUTHOR("Hiroshi DOYU "); MODULE_ALIAS("platform:tegra-gart"); -- 2.16.3