From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) (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 C58DB15AA for ; Thu, 15 Sep 2022 03:06:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1663211170; x=1694747170; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=WZZZSPl+QBxBcZfZhpMsL4YrZVmhzfuac91HSUV9DNc=; b=lVNJmtmtKwtz87aNa3UVPDFODWEekkx6wwHtEkhtA1BGTxE4yYeoz07m H4AQOSMkjHvrRBU+dt52x+yPtFt15C6xYQ4Qx5EurL9W+yKODOqMgelHg FvNymlEPEjx7IfeQZeNclTjuPdCObj0/sZUCOX+1djM5huMhDlkzows1X zeKkd74GI7AjyqiM9elILn3u5JaZOTKD1QYBET7zkCHI37y2KzNg1ynY2 WPNuUN46hinHNqk59lWgfjOPfnL5TvxCiMOdexBc6n6nH1ITPL4nCzNoU q4i9e0FVDNzTshUDxI86EJB4VYCzLFkkDTMk1aqL3VGlzkkdnDCyUhXZu w==; X-IronPort-AV: E=McAfee;i="6500,9779,10470"; a="360337390" X-IronPort-AV: E=Sophos;i="5.93,316,1654585200"; d="scan'208";a="360337390" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Sep 2022 20:06:10 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.93,316,1654585200"; d="scan'208";a="759453213" Received: from allen-box.sh.intel.com (HELO [10.239.159.48]) ([10.239.159.48]) by fmsmga001.fm.intel.com with ESMTP; 14 Sep 2022 20:06:08 -0700 Message-ID: <5415d383-5442-a127-bdab-fce9e9b7a3b2@linux.intel.com> Date: Thu, 15 Sep 2022 11:00:21 +0800 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Cc: baolu.lu@linux.intel.com, Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] iommu/vt-d: Enable PASID during iommu device probe Content-Language: en-US To: Ethan Zhao , iommu@lists.linux.dev References: <20220912024826.1684913-1-baolu.lu@linux.intel.com> <046916aa-980c-c40d-1163-6ab839248201@linux.intel.com> From: Baolu Lu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/14/22 4:59 PM, Ethan Zhao wrote: >>> What the error path would be if this code runs on some old platforms >>> don't >>> >>> support PASID, would you print out "this platform doesn't suppor >>> PASID" and >>> >>> give users an interface function to query if the PASID cap of iommu >>> is enabled >>> >>> and if not why ? >> >> It's not an error case if the IOMMU doesn't support PASID. But it's an >> error case if any device drivers call PASID related IOMMU interfaces >> (for example, iommu_domain_attach/detach_dev_pasid()). The corresponding >> error code will be returned to the drivers. >> > So iommu driver withdraws the flexibility/rights from device driver > about the > > ability to enable PASID, looks much more *integrated* iommu works as > relation No. This patch doesn't withdraw anything. It's just a code refactoring. > > controller in device-iommu-domain by enabling PASID in iommu probe stage > > by default -- iommu decides to enable PASID or not though device-iommu- > > domain might not work ? or they should work because they are hard-wired > > together (device - iommu) even device is hotpluged later. > I may not get you exactly. :-) Some IOMMU features reply on PASID capabilities on both IOMMU and device. The IOMMU drivers enumerate the capabilities and enable them if they are supported. Best regards, baolu