From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qt1-f169.google.com (mail-qt1-f169.google.com [209.85.160.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CCD9C321F5F for ; Sun, 26 Apr 2026 13:30:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777210231; cv=none; b=SVAoAjOTKjnPe3ixcBqOMsmxdGsk72RXV+mTuiBr5mdsnB47/qqxfwVHcFy4p5hx4fc706D+FM+Gn/Gef6NdW4+hnx00ISWuCtqFawYUP6K953d9UvHIDMp7eeDXXDPOMvCTTxbFJJIB4EChqpNc7/TbCXV5ukdDAhINBdL1sJw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777210231; c=relaxed/simple; bh=WjDzpbIBR3ZhSTR1LHNfWgthm8tzVuTmUuZKaNFMUWI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=m9iEPML/I7LSfA3NAJeHYVVu3rf0BZk7KdFqwFLPW/sZ1Re9xleLrXuSx/fUf5UdGitxdYfVrytbLZQbRA+/tjNYOBuxYLm6QvQvjTMGgQtVLo+/YL453w+hVcQLkqoZ7Rmxx8j5WrslgwO4vG60jPa3ryUXLwUHVCDfBoKLv1Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca; spf=pass smtp.mailfrom=ziepe.ca; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b=TzNfD9Ku; arc=none smtp.client-ip=209.85.160.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ziepe.ca Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="TzNfD9Ku" Received: by mail-qt1-f169.google.com with SMTP id d75a77b69052e-50335b926c2so73240191cf.2 for ; Sun, 26 Apr 2026 06:30:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1777210229; x=1777815029; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=yt3A8pADO9ZJrlnKUWoV4EH8uD2s2dkOvSuk8HhB068=; b=TzNfD9Ku5vx323+kFxxA01urtmaBdhsRC5obgOzZqadWKGELl3LxZR2scs1Ky46VN1 9TIoMCgqR3Bmq9n3L2HB2uiGW04s+x7vo92irYaT4uZ0ju7lJYfS9fcfLbCM0PuAHWEQ ZLDyAJHVugRue+deTPdxNjUAip5H6DCwywbNEx6TzsfB1lJLosR8tdxz8y6HUloSMbXx glk8INBD0E84XbFLP7aUoO2D4pF5orSefwwl+YtqE6m3jDXl00H46XOT41gJ3n3bUsFk h6KObHQ9lNJtRAUoF7x9wUFeYdaspsO3t+8ZU0T5LNyGJ6J3XZimsfTFXUphQCKSRxH4 xtTg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777210229; x=1777815029; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=yt3A8pADO9ZJrlnKUWoV4EH8uD2s2dkOvSuk8HhB068=; b=oSLzTlyELbHZ59jRqs9NLuPyCPYOrO3OQUX+78uQKXTlaUTs/3N1O86UQPPXH5c9jB O3RFkjezhbWVS98zzQfJ1Nkw8Qiw1vbNswGx1EA81SOqlf2PQ9o6HHj1xEgHJpzHKL23 UCWunl+VXQs8HS2eY5KvV2UuuPLHRbZrSMunPhy/AR3+3RWLYZX/3ZQL41B5yHQZpsnd nExcGke9KYrUx6GA2lZkEgM4Ji8ysKmd/q7VkotoC5PZ3cRb3ShFOhzAr6udhTRkhjhj lqbyjBNgS3mjaMq0o232U8L35qVTaEL2YIS2YHqsRmdw7nLY1y1S0ky1Q4lGY+8qPz0j 3hjA== X-Forwarded-Encrypted: i=1; AFNElJ+XZWXxYqRLC7ysUQJzK/pZDOmAO6E4ixAqbQt7hePHAKXFzqj22O+5+NlOB3aVJ2yiMYJbX5jw6edCzvI=@vger.kernel.org X-Gm-Message-State: AOJu0Yy0zeNWLFLqjUTOwVhhoRpobA9RSCka4DlTuJQ8P27fXP94xw43 IysSjyEQU4wmX6iuh5D1jZhElHPo3pTAEqGUIacDuwYJ1SqQ4lepE6yGTO1DFbh7PFp+zHsn4BI mBChR6cs= X-Gm-Gg: AeBDieskFE+P7R7eEMmsfkYV7ZdzUJZULayfh7zyd67s2Lf4r8QNb57505gqhXDNBTK uJN25y2+7DxN8YALOMs5AJdEmu9fY3IgH6cxOTHVMFuxOGD9tbPNihoPDMdQY1Lzf1dn1LtsSsd Wy+4hvyttQVtF+tj3A7t46RaGp0V9lboCJZ++o3FOdqgK2E96LExTmguoSeLM4t76ij+MJxCofT 4x8kDzEXyq7sY27nJwxs79/1xt4JS62tf3cbafUH70AW0HaEPQzF2a7l6lnHijDFqNHZKrKRA/v tmdethBzw0BAuZvW7Z7J844ogG2F5e6W9NgAPX25d5iRZpjQ69QQNwh0CB01orw7osl34tLS6uH ByDiuP7aaNh6jv/off7g4CnYBRwqE3HZIM4SxMwXE079AAqyASPzWkXbDmANsKP9DMsNdelBJZe CoivV87aDqmVOv59CPm+XjlssxqW9UhJaAtcACK1h/vQjV9zFX6vgqXPFcZqwTl4vlvIREaF0fI 7dDOtWvnJAimShz X-Received: by 2002:a05:622a:98e:b0:50d:7fe9:aa8a with SMTP id d75a77b69052e-50e36e9c3c8mr604759671cf.31.1777210228752; Sun, 26 Apr 2026 06:30:28 -0700 (PDT) Received: from ziepe.ca (crbknf0213w-47-54-130-67.pppoe-dynamic.high-speed.nl.bellaliant.net. [47.54.130.67]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50e394c1fddsm246449421cf.30.2026.04.26.06.30.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 26 Apr 2026 06:30:27 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wGzZ5-0000000EnQT-0zsZ; Sun, 26 Apr 2026 10:30:27 -0300 Date: Sun, 26 Apr 2026 10:30:27 -0300 From: Jason Gunthorpe To: "Tian, Kevin" Cc: Teddy Astie , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" , Xen-devel Subject: Re: How to express "externally managed" IOMMU domains for VFIO/IOMMUFD ? Message-ID: <20260426133027.GB3501894@ziepe.ca> References: <1776873531.8631fc262581453bbf619ec5b2062170.19db5ea67ab000f373@vates.tech> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Apr 23, 2026 at 08:01:50AM +0000, Tian, Kevin wrote: > > On Xen, we have a dedicated hypercalls for moving a device into another > > guest (so it no longer belongs in Dom0, at far as DMA is concerned). > > > > But it looks like there are no way to describe that idea of "attach that > > device to this VM" nor "the device is in a VM"; which makes that > > impracticable. > > > > There may be things that could be done with the vIOMMU objects, but > > there would be no "parent domain" in such case, as said earlier it > > doesn't exist in the IOMMU subsystem. > > > > What is expected to be done instead ? > > > > Teddy > > > > [1] https://www.youtube.com/watch?v=pLMGRgEJ-Eg > > > > It'd be much easier to collect comments if you can put plain words > to explain the problem rather than expecting other folks to watch > the video first... It sounds like CC and pkvm to me so I think it should re-use those mechanisms.. Jason