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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A261C41513 for ; Fri, 11 Aug 2023 01:15:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231354AbjHKBPy (ORCPT ); Thu, 10 Aug 2023 21:15:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35658 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229867AbjHKBPv (ORCPT ); Thu, 10 Aug 2023 21:15:51 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB3B79F; Thu, 10 Aug 2023 18:15:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1691716550; x=1723252550; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=+cNkmSq4sbVg58xl/B6iCnxVPlGtuyl7BHTC5IrVJmg=; b=jnhzXmrBaKRvjdNrqIxxDRxH6kWRwy4z1r8GzmuVN7n82Xd+8ZmgUzrr JpZtRqbm+xA+7EuMYGnHcmg1nXLoVn53YdXxhDUk3s+B5fsNLc6ErGZXe fnxlL6oWUroIIE2X/lDyPUqjdh/r5PWxM2PWlou4MmHI8+Wk4uSBl65ap mCCFHDKb0bcMVCiyBIKJ0ZHGSOc4WpdpFLqNvFK+LObpirdOLehmZm9ec hddE6nMDDkw9/ykpiSQAxSz/NyWxBVfDfxwX31VsrxnmKfyITppbGyPp6 80r7Kep+y/uOmU8CpMjtMVAhiZwpbVuRq3zJPlmcS3RucnmBV88Io3zbq g==; X-IronPort-AV: E=McAfee;i="6600,9927,10798"; a="356530276" X-IronPort-AV: E=Sophos;i="6.01,163,1684825200"; d="scan'208";a="356530276" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2023 18:15:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10798"; a="735608564" X-IronPort-AV: E=Sophos;i="6.01,163,1684825200"; d="scan'208";a="735608564" Received: from blu2-mobl.ccr.corp.intel.com (HELO [10.254.214.70]) ([10.254.214.70]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2023 18:15:47 -0700 Message-ID: <7694a4ea-4a08-2296-cd3a-593004de8718@linux.intel.com> Date: Fri, 11 Aug 2023 09:15:44 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Cc: baolu.lu@linux.intel.com, Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , Jean-Philippe Brucker , Nicolin Chen , Yi Liu , Jacob Pan , iommu@lists.linux.dev, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 03/12] iommu: Remove unrecoverable fault data Content-Language: en-US To: Jason Gunthorpe References: <20230727054837.147050-1-baolu.lu@linux.intel.com> <20230727054837.147050-4-baolu.lu@linux.intel.com> <28d86414-d684-b468-d0a9-5c429260e081@linux.intel.com> From: Baolu Lu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/8/11 0:46, Jason Gunthorpe wrote: > On Thu, Aug 10, 2023 at 10:27:21AM +0800, Baolu Lu wrote: >> On 2023/8/10 0:59, Jason Gunthorpe wrote: >>> On Thu, Jul 27, 2023 at 01:48:28PM +0800, Lu Baolu wrote: >>>> The unrecoverable fault data is not used anywhere. Remove it to avoid >>>> dead code. >>>> >>>> Suggested-by: Kevin Tian >>>> Signed-off-by: Lu Baolu >>>> --- >>>> include/linux/iommu.h | 70 +------------------------------------------ >>>> 1 file changed, 1 insertion(+), 69 deletions(-) >>> Do we plan to bring this back in some form? A driver specific fault >>> report via iommufd? >> I can hardly see the possibility. >> >> The only necessary dma fault messages are the offending address and the >> permissions. With these, the user space device model software knows that >> "a DMA fault was generated when the IOMMU hardware tried to translate >> the offending address with the given permissions". >> >> And then, the device model software will walk the page table and figure >> out what is missed before injecting the vendor-specific fault messages >> to the VM guest. > Avoiding walking the page table sounds like a pretty big win if we > could manage it by forwarding more event data.. Fair enough. We can discuss what kind of extra event data could be included later when we have real code for dma fault forwarding support in iommufd. Best regards, baolu