From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (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 C58F514AD29; Thu, 20 Feb 2025 02:13:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740017629; cv=none; b=DG13bQ8haVydB3k0wFpgoFmcpmuJ++C6RiJDq1Lnok7oOTlTjOJROfj8uiNYVUpyV+hiGU+407t0MnVgipQhhBUtPZ4hX1gYr2QQdcywHQHp6PbBkkkq1VVGwaGRReaBFRDLIBQbLUnITqIOvlU8mWNrePRmGWjYXdL8kp97NrM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740017629; c=relaxed/simple; bh=GBvD2bkSH/pQf3oXkciwQpaE+MUdAMS3a6Cb1EoRnIs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=YkoDqDGJ7UzIqKteM5XpOilgFvtKvV7vYVaHdJ5szlfGBAVlU8EV3StNW+0sOXS2B2CxiiYPzE9eVviqdIPkXu6LgVD4usC/UxWE/NVJCtSCCQ/d9z7H/NqglV3vq15xf04rY9wPEQNQc2YvUmB8bCdhOP811MUuueoZmP40MiU= 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=cZqyr/B/; arc=none smtp.client-ip=192.198.163.9 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="cZqyr/B/" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1740017628; x=1771553628; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=GBvD2bkSH/pQf3oXkciwQpaE+MUdAMS3a6Cb1EoRnIs=; b=cZqyr/B/ejIdGkrinOk7i3+gMvu64dTmm6jDnFIz1wRs+6i00Qgsjkn2 PF7f7m5jvuo1SQkU/a3JaDflAslQPs0gUkFGivLlObukeWOTXwZC3q2vM 4giJCFYFHzVapLwGKEaeK42FBG9YTCVTambrUCyeZvNUf7oHcXOkRSFBg sSW2ciHjcIHEhBWN2VFwbX1AI1V9rCLHa9th5CpKVaHCWxz9JEd7T+mPl nPeQ7Ojhrao10S8M8L2MjA0O7D9iFyb3ZBMf2YKUpV18zK6+Gjp8w3nTc 8W18xkexdAZ0geDJCpzwNJRJdEokPCdtVeq3Zb9NpgSOfGtIEojQUlP4d w==; X-CSE-ConnectionGUID: w4sOhzFrR6+paQ2DnBUdeA== X-CSE-MsgGUID: UpX060Z3RiaY0VdDMIbe0g== X-IronPort-AV: E=McAfee;i="6700,10204,11350"; a="51424639" X-IronPort-AV: E=Sophos;i="6.13,300,1732608000"; d="scan'208";a="51424639" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Feb 2025 18:13:47 -0800 X-CSE-ConnectionGUID: dxxRzlLRTLidTKr9odiFmQ== X-CSE-MsgGUID: 05003GDaRq+1FPxr5vBMHQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,300,1732608000"; d="scan'208";a="119995677" Received: from allen-sbox.sh.intel.com (HELO [10.239.159.30]) ([10.239.159.30]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Feb 2025 18:13:41 -0800 Message-ID: <7027fb3a-dfb4-40ae-ac9c-5ea1dcd57746@linux.intel.com> Date: Thu, 20 Feb 2025 10:10:36 +0800 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 00/12] Initial support for SMMUv3 nested translation To: "Tian, Kevin" , Jason Gunthorpe Cc: Zhangfei Gao , "acpica-devel@lists.linux.dev" , "iommu@lists.linux.dev" , Joerg Roedel , "kvm@vger.kernel.org" , Len Brown , "linux-acpi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Lorenzo Pieralisi , "Rafael J. Wysocki" , "Moore, Robert" , Robin Murphy , Sudeep Holla , Will Deacon , Alex Williamson , Donald Dutile , Eric Auger , Hanjun Guo , Jean-Philippe Brucker , Jerry Snitselaar , Moritz Fischer , Michael Shavit , Nicolin Chen , "patches@lists.linux.dev" , "Wysocki, Rafael J" , Shameerali Kolothum Thodi , Mostafa Saleh References: <20241113164316.GL35230@nvidia.com> <6ed97a10-853f-429e-8506-94b218050ad3@linux.intel.com> <20241115175522.GA35230@nvidia.com> <20250122192622.GA965540@nvidia.com> <284dd081-8d53-45ef-ae18-78b0388c98ca@linux.intel.com> <20250213184317.GB3886819@nvidia.com> <20250214124150.GF3886819@nvidia.com> <58e7fbee-6688-4a49-8b7a-f0e81e6562db@linux.intel.com> <20250218130333.GA4099685@nvidia.com> Content-Language: en-US From: Baolu Lu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/19/25 16:34, Tian, Kevin wrote: >> From: Baolu Lu >> Sent: Wednesday, February 19, 2025 10:10 AM >> >> On 2/18/25 21:03, Jason Gunthorpe wrote: >>> On Sat, Feb 15, 2025 at 05:53:13PM +0800, Baolu Lu wrote: >>>> On 2/14/25 20:41, Jason Gunthorpe wrote: >>>>> On Fri, Feb 14, 2025 at 01:39:52PM +0800, Baolu Lu wrote: >>>>> >>>>>> When the IOMMU is working in scalable mode, PASID and PRI are >> supported. >>>>>> ATS will always be enabled, even if the identity domain is attached to >>>>>> the device, because the PASID might use PRI, which depends on ATS >>>>>> functionality. This might not be the best choice, but it is the >>>>>> simplest and functional. >>>>> The arm driver keeps track of things and enables ATS when PASIDs are >>>>> present >>>> I am not aware of any VT-d hardware implementation that supports >>>> scalable mode but not PASID. If there were one, it would be worthwhile >>>> to add an optimization to avoid enabling ATS during probe if PASID is >>>> not supported. >>> I mean domains attached to PASIDs that need PRI/ATS/etc >> >> Yeah, that's a better solution. The PCI PRI/ATS features are only >> enabled when a domain that requires them is attached to it. I will >> consider it in the Intel driver later. >> > > I didn't get the connection here. ATS can run w/o PASID per PCIe > spec. Why do we want to add a dependency on PASID here? It's due to PRI, which depends on ATS. The original topic is: when an identity domain is attached to the device and the device has no PASID support, then ATS might be disabled because ATS isn't supposed to provide much benefit in this case. Otherwise, ATS should be enabled because: - It benefits performance when the domain is a paging domain. - A domain attached to a PASID might use PRI, thus requiring ATS to be on. The proposed solution is to use a reference count for ATS enablement, similar to how we handle iopf in another series. ATS is enabled as long as any domain requires it and disabled if no domain requires it. Hope it explains. Thanks, baolu