Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758540AbbKSNpw (ORCPT ); Thu, 19 Nov 2015 08:45:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40958 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757783AbbKSNpu (ORCPT ); Thu, 19 Nov 2015 08:45:50 -0500 Date: Thu, 19 Nov 2015 15:45:44 +0200 From: "Michael S. Tsirkin" To: Andy Lutomirski Cc: linux-kernel@vger.kernel.org, Joerg Roedel , Christian Borntraeger , Cornelia Huck , Sebastian Ott , Paolo Bonzini , Christoph Hellwig , benh@kernel.crashing.org, KVM , dwmw2@infradead.org, Martin Schwidefsky , linux-s390 , virtualization@lists.linux-foundation.org Subject: Re: [PATCH v3 0/3] virtio DMA API core stuff Message-ID: <20151119153821-mutt-send-email-mst@redhat.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2034 Lines: 51 On Tue, Oct 27, 2015 at 11:38:57PM -0700, Andy Lutomirski wrote: > This switches virtio to use the DMA API unconditionally. I'm sure > it breaks things, but it seems to work on x86 using virtio-pci, with > and without Xen, and using both the modern 1.0 variant and the > legacy variant. So thinking hard about it, I don't see any real drawbacks to making this conditional on a new feature bit, that Xen can then set. As a bonus, host can distinguish between old and new guests using the feature bit, even though making driver *control* whether IOMMU is bypassed makes userspace drivers unsafe, so might not be a good idea. A tiny bit more code but not by much, and we clearly won't be breaking anything that's not already broken, and we will be able to drop the extra code later if we think it's a good idea. I'll run this by the virtio TC on OASIS next week so we can reserve a feature bit. > Changes from v2: > - Fix really embarrassing bug. This version actually works. > > Changes from v1: > - Fix an endian conversion error causing a BUG to hit. > - Fix a DMA ordering issue (swiotlb=force works now). > - Minor cleanups. > > Andy Lutomirski (3): > virtio_net: Stop doing DMA from the stack > virtio_ring: Support DMA APIs > virtio_pci: Use the DMA API > > drivers/net/virtio_net.c | 53 +++++++---- > drivers/virtio/Kconfig | 2 +- > drivers/virtio/virtio_pci_common.h | 3 +- > drivers/virtio/virtio_pci_legacy.c | 19 +++- > drivers/virtio/virtio_pci_modern.c | 34 +++++-- > drivers/virtio/virtio_ring.c | 187 ++++++++++++++++++++++++++++++------- > tools/virtio/linux/dma-mapping.h | 17 ++++ > 7 files changed, 246 insertions(+), 69 deletions(-) > create mode 100644 tools/virtio/linux/dma-mapping.h > > -- > 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/