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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 29952C31E46 for ; Wed, 12 Jun 2019 19:01:41 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (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 ED689215EA for ; Wed, 12 Jun 2019 19:01:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ED689215EA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id BDAD722DE; Wed, 12 Jun 2019 19:01:40 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 69772220C for ; Wed, 12 Jun 2019 18:59:01 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id F1470E6 for ; Wed, 12 Jun 2019 18:59:00 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Jun 2019 11:59:00 -0700 X-ExtLoop1: 1 Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga004.jf.intel.com with ESMTP; 12 Jun 2019 11:59:00 -0700 Date: Wed, 12 Jun 2019 12:02:09 -0700 From: Jacob Pan To: Jean-Philippe Brucker Subject: Re: [PATCH] iommu: Add padding to struct iommu_fault Message-ID: <20190612120209.29e90efe@jacob-builder> In-Reply-To: <20190612175938.16428-1-jean-philippe.brucker@arm.com> References: <20190612131143.GF21613@8bytes.org> <20190612175938.16428-1-jean-philippe.brucker@arm.com> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Cc: iommu@lists.linux-foundation.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 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 Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Wed, 12 Jun 2019 18:59:38 +0100 Jean-Philippe Brucker wrote: > Ease future extensions of struct iommu_fault_page_request and struct > iommu_fault_unrecoverable by adding a few bytes of padding. That way, > a new field can be added to either of these structures by simply > introducing a new flag. To extend it after the size limit is reached, > a new fault reporting structure will have to be negotiated with > userspace. > > With 56 bytes of padding, the total size of iommu_fault is 64 bytes > and fits in a cache line on a lot of contemporary machines, while > providing 16 and 24 bytes of extension to structures > iommu_fault_page_request and iommu_fault_unrecoverable respectively. > > Signed-off-by: Jean-Philippe Brucker > --- > include/uapi/linux/iommu.h | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h > index f45d8e9e59c3..fc00c5d4741b 100644 > --- a/include/uapi/linux/iommu.h > +++ b/include/uapi/linux/iommu.h > @@ -105,15 +105,17 @@ struct iommu_fault_page_request { > * @type: fault type from &enum iommu_fault_type > * @padding: reserved for future use (should be zero) > * @event: fault event, when @type is %IOMMU_FAULT_DMA_UNRECOV > * @prm: Page Request message, when @type is %IOMMU_FAULT_PAGE_REQ > + * @padding2: sets the fault size to allow for future extensions > */ > struct iommu_fault { > __u32 type; > __u32 padding; > union { > struct iommu_fault_unrecoverable event; > struct iommu_fault_page_request prm; > + __u8 padding2[56]; > }; > }; > Acked-by: Jacob Pan > /** [Jacob Pan] _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu