From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Wang Subject: Re: [PATCH v18 06/10] virtio_ring: add a new API, virtqueue_add_one_desc Date: Fri, 01 Dec 2017 16:06:05 +0800 Message-ID: <5A210D6D.3090402@intel.com> References: <1511963726-34070-1-git-send-email-wei.w.wang@intel.com> <1511963726-34070-7-git-send-email-wei.w.wang@intel.com> <20171130213231-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, akpm@linux-foundation.org, mawilcox@microsoft.com, david@redhat.com, penguin-kernel@I-love.SAKURA.ne.jp, cornelia.huck@de.ibm.com, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, willy@infradead.org, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu@aliyun.com, nilal@redhat.com, riel@redhat.com To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20171130213231-mutt-send-email-mst@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 12/01/2017 03:38 AM, Michael S. Tsirkin wrote: > On Wed, Nov 29, 2017 at 09:55:22PM +0800, Wei Wang wrote: >> Current virtqueue_add API implementation is based on the scatterlist >> struct, which uses kaddr. This is inadequate to all the use case of >> vring. For example: >> - Some usages don't use IOMMU, in this case the user can directly pass >> in a physical address in hand, instead of going through the sg >> implementation (e.g. the VIRTIO_BALLOON_F_SG feature) >> - Sometimes, a guest physical page may not have a kaddr (e.g. high >> memory) but need to use vring (e.g. the VIRTIO_BALLOON_F_FREE_PAGE_VQ >> feature) >> >> The new API virtqueue_add_one_desc enables the caller to assign a vring >> desc with a physical address and len. Also, factor out the common code >> with virtqueue_add in vring_set_avail. >> >> Signed-off-by: Wei Wang >> Cc: Michael S. Tsirkin > You previously managed without this patch, and it's preferable > IMHO since this patchset is already too big. > > I don't really understand what is wrong with virtio_add_sgs + sg_set_page. > I don't think is assumes a kaddr. > OK, I will use the previous method to send sgs. Please have a check if there are other things need to be improved. Best, Wei