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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 54F38CCA47B for ; Thu, 14 Jul 2022 08:12:03 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Lk6f95QGQz3cdm for ; Thu, 14 Jul 2022 18:12:01 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.ru (client-ip=107.174.27.60; helo=ozlabs.ru; envelope-from=aik@ozlabs.ru; receiver=) Received: from ozlabs.ru (ozlabs.ru [107.174.27.60]) by lists.ozlabs.org (Postfix) with ESMTP id 4Lk6dl3nmBz3bx3 for ; Thu, 14 Jul 2022 18:11:39 +1000 (AEST) Received: from fstn1-p1.ozlabs.ibm.com. (localhost [IPv6:::1]) by ozlabs.ru (Postfix) with ESMTP id E5797804CB; Thu, 14 Jul 2022 04:11:34 -0400 (EDT) From: Alexey Kardashevskiy To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH kernel] powerpc/iommu: Fix iommu_table_in_use for a small default DMA window case Date: Thu, 14 Jul 2022 18:11:19 +1000 Message-Id: <20220714081119.3714605-1-aik@ozlabs.ru> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , Leonardo Bras , Fabiano Rosas Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" The existing iommu_table_in_use() helper checks if the kernel is using any of TCEs. There are some reserved TCEs: 1) the very first one if DMA window starts from 0 to avoid having a zero but still valid DMA handle; 2) it_reserved_start..it_reserved_end to exclude MMIO32 window in case the default window spans across that - this is the default for the first DMA window on PowerNV. When 1) is the case and 2) is not the helper does not skip 1) and returns wrong status. This only seems occurring when passing through a PCI device to a nested guest (not something we support really well) so it has not been seen before. This fixes the bug by adding a special case for no MMIO32 reservation. Fixes: 3c33066a2190 ("powerpc/kernel/iommu: Add new iommu_table_in_use() helper") Signed-off-by: Alexey Kardashevskiy --- arch/powerpc/kernel/iommu.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c index 7e56ddb3e0b9..caebe1431596 100644 --- a/arch/powerpc/kernel/iommu.c +++ b/arch/powerpc/kernel/iommu.c @@ -775,6 +775,11 @@ bool iommu_table_in_use(struct iommu_table *tbl) /* ignore reserved bit0 */ if (tbl->it_offset == 0) start = 1; + + /* Simple case with no reserved MMIO32 region */ + if (!tbl->it_reserved_start && !tbl->it_reserved_end) + return find_next_bit(tbl->it_map, tbl->it_size, start) != tbl->it_size; + end = tbl->it_reserved_start - tbl->it_offset; if (find_next_bit(tbl->it_map, end, start) != end) return true; -- 2.30.2