From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 9DEB619F466; Tue, 1 Oct 2024 08:47:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727772448; cv=none; b=gaJYcnRJdgnPpmPJA9dRpS7bZBAlHpC0pzcyR6ZAzNsBQqWzCcMN2e8/pLajmLyjArtX6XYs78UauNkXQKDKQJNz8COgb/dytFxWCqB7KEwMyHJww7yDG2zlnBvE+H1qKRgAXTwLQs9SroKBbwt4ncs0o/YQtbmIAFZah6jrNwo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727772448; c=relaxed/simple; bh=+gaPzNsCZQOr4VCJ8VidECoUZMzdtDuIZk/Lnk/iwW4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=guDufRE4LnwZPvsrCegdrmScXYtdNUSdaGI/zRAfhbOoltMvBqSX5IUXlqjYoTeyA0Of/P3NOAvkUfO0ssLYvruCnjQDFv2v6E0ghxyW9p7OtEvV4lOamaoOrwVfSm1BquKlArQrR8fVPu1NCu58Vvpui72bmG2SwiGUliAUZFQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=rWN2w4Jr; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="rWN2w4Jr" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=q1nkpS6A5NXCi237YqhQxNqBbwH4xTO/TAMf/Y2ZkoE=; b=rWN2w4Jr5zbVYy8b6B9XdGXa/U f+mcqFz/ct2x5PguuXGbA/XQmGiOcUKODU9abUZ4DXDqEx5bf8BEcIIVtEzljI9dlGiirIyEtkN6Z 6eUgflJtnSPq2jXrCxmMciNitfQprnL4y+Fz+RyqbEqzxxWk6Tn3MsYSDLEswL9WW6ld05wJ81gMY nEdDT6omPrBHKn8JU2wAyX9bJaQVJlbZjuUJes3DkhJ8tkPrKUrHt8X+cdKTe3F0/A3dak6cLr3rs g/XRKEWnCPjYrJEWh3KOKDKi+D2Z1slM55blII4GM9AOpgz1rzv5+kRhciwsi3jpt22tp/29ScivR XOwTlcPQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1svYXW-000000027nP-3dbR; Tue, 01 Oct 2024 08:47:26 +0000 Date: Tue, 1 Oct 2024 01:47:26 -0700 From: Christoph Hellwig To: Srujana Challa Cc: virtualization@lists.linux.dev, kvm@vger.kernel.org, mst@redhat.com, jasowang@redhat.com, eperezma@redhat.com, ndabilpuram@marvell.com, jerinj@marvell.com Subject: Re: [PATCH v2 0/2] vhost-vdpa: Add support for NO-IOMMU mode Message-ID: References: <20240920140530.775307-1-schalla@marvell.com> Precedence: bulk X-Mailing-List: kvm@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: <20240920140530.775307-1-schalla@marvell.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Fri, Sep 20, 2024 at 07:35:28PM +0530, Srujana Challa wrote: > This patchset introduces support for an UNSAFE, no-IOMMU mode in the > vhost-vdpa driver. When enabled, this mode provides no device isolation, > no DMA translation, no host kernel protection, and cannot be used for > device assignment to virtual machines. It requires RAWIO permissions > and will taint the kernel. > > This mode requires enabling the "enable_vhost_vdpa_unsafe_noiommu_mode" > option on the vhost-vdpa driver and also negotiate the feature flag > VHOST_BACKEND_F_NOIOMMU. This mode would be useful to get > better performance on specifice low end machines and can be leveraged > by embedded platforms where applications run in controlled environment. ... and is completely broken and dangerous.