From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <nouveau-bounces@lists.freedesktop.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.lore.kernel.org (Postfix) with ESMTPS id C89ACC7EE2A
	for <nouveau@archiver.kernel.org>; Fri, 19 May 2023 04:11:46 +0000 (UTC)
Received: from gabe.freedesktop.org (localhost [127.0.0.1])
	by gabe.freedesktop.org (Postfix) with ESMTP id 8D50B10E5B7;
	Fri, 19 May 2023 04:11:45 +0000 (UTC)
X-Greylist: delayed 452 seconds by postgrey-1.36 at gabe;
 Fri, 19 May 2023 04:11:42 UTC
Received: from verein.lst.de (verein.lst.de [213.95.11.211])
 by gabe.freedesktop.org (Postfix) with ESMTPS id BC90410E038
 for <nouveau@lists.freedesktop.org>; Fri, 19 May 2023 04:11:42 +0000 (UTC)
Received: by verein.lst.de (Postfix, from userid 2407)
 id 6AB6268AFE; Fri, 19 May 2023 06:04:05 +0200 (CEST)
Date: Fri, 19 May 2023 06:04:05 +0200
From: Christoph Hellwig <hch@lst.de>
To: Marek =?iso-8859-1?Q?Marczykowski-G=F3recki?=
 <marmarek@invisiblethingslab.com>
Message-ID: <20230519040405.GA10818@lst.de>
References: <20230518134253.909623-1-hch@lst.de>
 <20230518134253.909623-3-hch@lst.de> <ZGZr/xgbUmVqpOpN@mail-itl>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <ZGZr/xgbUmVqpOpN@mail-itl>
User-Agent: Mutt/1.5.17 (2007-11-01)
Subject: Re: [Nouveau] [PATCH 2/4] x86: always initialize xen-swiotlb when
 xen-pcifront is enabling
X-BeenThere: nouveau@lists.freedesktop.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Nouveau development list <nouveau.lists.freedesktop.org>
List-Unsubscribe: <https://lists.freedesktop.org/mailman/options/nouveau>,
 <mailto:nouveau-request@lists.freedesktop.org?subject=unsubscribe>
List-Archive: <https://lists.freedesktop.org/archives/nouveau>
List-Post: <mailto:nouveau@lists.freedesktop.org>
List-Help: <mailto:nouveau-request@lists.freedesktop.org?subject=help>
List-Subscribe: <https://lists.freedesktop.org/mailman/listinfo/nouveau>,
 <mailto:nouveau-request@lists.freedesktop.org?subject=subscribe>
Cc: Juergen Gross <jgross@suse.com>,
 Stefano Stabellini <sstabellini@kernel.org>, nouveau@lists.freedesktop.org,
 Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
 linux-kernel@vger.kernel.org, iommu@lists.linux.dev,
 Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
 Ben Skeggs <bskeggs@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
 xen-devel@lists.xenproject.org, Thomas Gleixner <tglx@linutronix.de>,
 Christoph Hellwig <hch@lst.de>
Errors-To: nouveau-bounces@lists.freedesktop.org
Sender: "Nouveau" <nouveau-bounces@lists.freedesktop.org>

On Thu, May 18, 2023 at 08:18:39PM +0200, Marek Marczykowski-Górecki wrote:
> On Thu, May 18, 2023 at 03:42:51PM +0200, Christoph Hellwig wrote:
> > Remove the dangerous late initialization of xen-swiotlb in
> > pci_xen_swiotlb_init_late and instead just always initialize
> > xen-swiotlb in the boot code if CONFIG_XEN_PCIDEV_FRONTEND is enabled.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Doesn't it mean all the PV guests will basically waste 64MB of RAM
> by default each if they don't really have PCI devices?

If CONFIG_XEN_PCIDEV_FRONTEND is enabled, and the kernel's isn't booted
with swiotlb=noforce, yes.