From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 635B21CD13 for ; Fri, 31 May 2024 06:02:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.20 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717135368; cv=none; b=aPPCekFXO45kpR3yXOB79nM01v6tPSOcaGLpES125IeevcSUEUENfpcVwBGhbZpRSwLb5fnlQ4993nciV5aeX1YceaY9/rSoYFcULHTswR1j4h7TY26QLY9MI2KAhrNvqw93SopoCva6+C9jdP35wNzelGYlEpD693qmhvgjMRs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717135368; c=relaxed/simple; bh=ybwUS6RtWP/25t4kttVVL9hVeT6Fp8bPYKJR9Xwq21Y=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=PL1ycyurrRrfmOdq0qIQS7QDFXM1G+z0LjiRaZFUgOYWjbquough/Rwobtggy3PBq4gt71Scm1323z+sOJdhfuWa0qani+HfZiFl+1+IgI24APAC8eHo9d8vRWsmPVr3atBBzh3MfXllLvn6lcRS4837nbIRTAm8V5YXaumKJMk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Yzp6GSIH; arc=none smtp.client-ip=198.175.65.20 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Yzp6GSIH" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1717135368; x=1748671368; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=ybwUS6RtWP/25t4kttVVL9hVeT6Fp8bPYKJR9Xwq21Y=; b=Yzp6GSIHtBtJCByAn/q603xTx9521rxJ1J5jPnAUkF2P/BzEgMxSQrnM uA62wfVilmRy3TzDR04L4qLzt1aZArKBtZkc8AY45puPzw2Tv7C4yeA3e kAimg22aH9usD9xmKPuP7a6+rJs1zyXnGiRufApJKUPpC1z4ndbeakKHF f5BCdLpE3TZXeFh5V+srNZJz4tC2joVwEUpHixxrZlsr0gPWNMgJ14DkS aYaNMMP5F2lYzbhsq4OzzNZbtKWlwpOchbD1/aRNuGJ4NgNTFN72zrLYf czRptdT41fXiAdXpK/FsNuce2w6FHNfiLfNOQZjrctUuM3zxPc88Nbo93 w==; X-CSE-ConnectionGUID: ec9oc40bSWihv7ehxNjEJQ== X-CSE-MsgGUID: qTCXWMk1QVuJuN5eRQ19aA== X-IronPort-AV: E=McAfee;i="6600,9927,11088"; a="13509421" X-IronPort-AV: E=Sophos;i="6.08,203,1712646000"; d="scan'208";a="13509421" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa112.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 May 2024 23:02:47 -0700 X-CSE-ConnectionGUID: fMZJ/pUwTXqKV30ojXQ/RA== X-CSE-MsgGUID: CO2gmYVVR3yFgXq5Fsh8Rw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,203,1712646000"; d="scan'208";a="41127729" Received: from unknown (HELO [10.239.159.127]) ([10.239.159.127]) by orviesa004.jf.intel.com with ESMTP; 30 May 2024 23:02:41 -0700 Message-ID: <34d23852-ea68-414e-92ce-61dcfe6a0368@linux.intel.com> Date: Fri, 31 May 2024 14:00:34 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: baolu.lu@linux.intel.com, David Airlie , Daniel Vetter , Kalle Valo , Bjorn Andersson , Mathieu Poirier , Alex Williamson , mst@redhat.com, Jason Wang , Thierry Reding , Jonathan Hunter , Mikko Perttunen , iommu@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 00/20] iommu: Refactoring domain allocation interface To: Yi Liu , Joerg Roedel , Will Deacon , Robin Murphy , Jason Gunthorpe , Kevin Tian References: <20240529053250.91284-1-baolu.lu@linux.intel.com> <7af4fee2-1b37-4eb8-9d03-8b1a402ec00b@intel.com> Content-Language: en-US From: Baolu Lu In-Reply-To: <7af4fee2-1b37-4eb8-9d03-8b1a402ec00b@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 5/31/24 11:16 AM, Yi Liu wrote: > On 2024/5/29 20:02, Baolu Lu wrote: >> On 2024/5/29 17:03, Yi Liu wrote: >>> On 2024/5/29 13:32, Lu Baolu wrote: >>>> The IOMMU subsystem has undergone some changes, including the removal >>>> of iommu_ops from the bus structure. Consequently, the existing domain >>>> allocation interface, which relies on a bus type argument, is no longer >>>> relevant: >>>> >>>>      struct iommu_domain *iommu_domain_alloc(struct bus_type *bus) >>>> >>>> This series is designed to refactor the use of this interface. It >>>> proposes two new interfaces to replace iommu_domain_alloc(): >>>> >>>> - iommu_user_domain_alloc(): This interface is intended for allocating >>>>    iommu domains managed by userspace for device passthrough scenarios, >>>>    such as those used by iommufd, vfio, and vdpa. It clearly indicates >>>>    that the domain is for user-managed device DMA. >>> >>> user paging domain? It looks to me user domain includes the nested >>> domains >>> as well. >> >> Yes, nested domain is a user domain. The iommu driver should implement >> iommu_ops->domain_alloc_user for nested domain allocation. > > will it be more clear to name iommu_user_domain_alloc() be > iommu_user_paging_domain_alloc() as it is mainly for paging domain > allocation? That might be better; let's wait and see if there's another option. > >>> >>>>    If an IOMMU driver does not implement iommu_ops->domain_alloc_user, >>>>    this interface will rollback to the generic paging domain >>>> allocation. >>>> >>>> - iommu_paging_domain_alloc(): This interface is for allocating iommu >>>>    domains managed by kernel drivers for kernel DMA purposes. It >>>> takes a >>>>    device pointer as a parameter, which better reflects the current >>>>    design of the IOMMU subsystem. >>>> >>>> The majority of device drivers currently using iommu_domain_alloc() do >>>> so to allocate a domain for a specific device and then attach that >>>> domain to the device. These cases can be straightforwardly migrated to >>>> the new interfaces. >>>> >>>> However, there are some drivers with more complex use cases that do >>>> not fit neatly into this new scheme. For example: >>>> >>>> $ git grep "= iommu_domain_alloc" >>>> arch/arm/mm/dma-mapping.c:      mapping->domain = >>>> iommu_domain_alloc(bus); >>>> drivers/gpu/drm/rockchip/rockchip_drm_drv.c:    private->domain = >>>> iommu_domain_alloc(private->iommu_dev->bus); >>>> drivers/gpu/drm/tegra/drm.c:            tegra->domain = >>>> iommu_domain_alloc(&platform_bus_type); >>>> drivers/infiniband/hw/usnic/usnic_uiom.c:       pd->domain = domain >>>> = iommu_domain_alloc(dev->bus); >>>> >>>> This series leave those cases unchanged and keep iommu_domain_alloc() >>>> for their usage. But new drivers should not use it anymore. >>> >>> does it mean there is still domains allocated via iommu_domain_alloc() >>> on VT-d platform? >> >> I think the drivers mentioned above do not run on x86 platforms, or do >> they? > > cool. BTW. I know out-of-tree drivers are not counted in upstream review. > Just out of curious, is there a formal way to let such drivers know it is > no longer allowed to use iommu_domain_alloc() on VT-d? As Robin suggested, we should try to remove iommu_domain_alloc() from the tree in this series. Best regards, baolu