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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B4BCC433F5 for ; Thu, 30 Sep 2021 15:17:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C8F361882 for ; Thu, 30 Sep 2021 15:17:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245237AbhI3PTZ (ORCPT ); Thu, 30 Sep 2021 11:19:25 -0400 Received: from mga09.intel.com ([134.134.136.24]:11227 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245339AbhI3PTY (ORCPT ); Thu, 30 Sep 2021 11:19:24 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10123"; a="225250609" X-IronPort-AV: E=Sophos;i="5.85,336,1624345200"; d="scan'208";a="225250609" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Sep 2021 08:17:41 -0700 X-IronPort-AV: E=Sophos;i="5.85,336,1624345200"; d="scan'208";a="487364233" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Sep 2021 08:17:41 -0700 Date: Thu, 30 Sep 2021 08:21:21 -0700 From: Jacob Pan To: "Campin, Mike" Cc: Jason Gunthorpe , "iommu@lists.linux-foundation.org" , LKML , Joerg Roedel , Christoph Hellwig , "Tian, Kevin" , "Luck, Tony" , "Jiang, Dave" , "Raj, Ashok" , "Kumar, Sanjay K" , Thomas Gleixner , jacob.jun.pan@linux.intel.com Subject: Re: [RFC 0/7] Support in-kernel DMA with PASID and SVA Message-ID: <20210930082121.444299be@jacob-builder> In-Reply-To: References: <1632256181-36071-1-git-send-email-jacob.jun.pan@linux.intel.com> <20210929123437.721991dc@jacob-builder> <20210929193953.GX964074@nvidia.com> <20210929155720.794b6e65@jacob-builder> <20210929234301.GC964074@nvidia.com> Organization: OTC X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mike, On Thu, 30 Sep 2021 14:22:34 +0000, "Campin, Mike" wrote: > I need support for mixed user PASID, kernel PASID and non-PASID use cases > in the driver. > This specific RFC is for kernel PASID only. User PASID native use is supported under SVA lib kernel API and /dev/uacce UAPI or driver specific char dev. Guest PASID is being developed under the new /dev/iommu framework. Non-PASID kernel use should be under DMA API unchanged from the driver's POV. In fact, this proposal will map non-PASID and PASID DMA identically. Thanks, Jacob > -----Original Message----- > From: Jason Gunthorpe > Sent: Wednesday, September 29, 2021 4:43 PM > To: Jacob Pan > Cc: iommu@lists.linux-foundation.org; LKML > ; Joerg Roedel ; Christoph > Hellwig ; Tian, Kevin ; Luck, > Tony ; Jiang, Dave ; Raj, > Ashok ; Kumar, Sanjay K ; > Campin, Mike ; Thomas Gleixner > Subject: Re: [RFC 0/7] Support in-kernel DMA with > PASID and SVA > > On Wed, Sep 29, 2021 at 03:57:20PM -0700, Jacob Pan wrote: > > Hi Jason, > > > > On Wed, 29 Sep 2021 16:39:53 -0300, Jason Gunthorpe > > wrote: > > > On Wed, Sep 29, 2021 at 12:37:19PM -0700, Jacob Pan wrote: > > > > > > > For #2, it seems we can store the kernel PASID in struct device. > > > > This will preserve the DMA API interface while making it PASID > > > > capable. Essentially, each PASID capable device would have two > > > > special global > > > > PASIDs: > > > > - PASID 0 for DMA request w/o PASID, aka RID2PASID > > > > - PASID 1 (randomly selected) for in-kernel DMA request w/ > > > > PASID > > > > > > This seems reasonable, I had the same thought. Basically just have > > > the driver issue some trivial call: > > > pci_enable_pasid_dma(pdev, &pasid) > > That would work, but I guess it needs to be an iommu_ call instead of > > pci_? > > Which ever makes sense.. The API should take in a struct pci_device and > return a PCI PASID - at least as a wrapper around a more generic immu api. > > > I think your suggestion is more precise, in case the driver does not > > want to do DMA w/ PASID, we can do less IOTLB flush (PASID 0 only). > > Since it is odd, and it may create overhead, I would do it only when > asked to do it > > > > Having multiple RID's pointing at the same IO page table is > > > something we expect iommufd to require so the whole thing should > > > ideally fall out naturally. > > > That would be the equivalent of attaching multiple devices to the same > > IOMMU domain. right? > > Effectively.. > > Jason Thanks, Jacob