From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH 3/3] virtio_pci: Use the DMA API for virtqueues Date: Wed, 27 Aug 2014 13:32:44 -0400 Message-ID: <20140827173244.GB5379@laptop.dumpdata.com> References: <3bf33716d8c9808c91ac9f38d967f97153383375.1409087794.git.luto@amacapital.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <3bf33716d8c9808c91ac9f38d967f97153383375.1409087794.git.luto@amacapital.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Archive: List-Post: To: Andy Lutomirski Cc: linux-s390@vger.kernel.org, "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, linux390@de.ibm.com List-ID: On Tue, Aug 26, 2014 at 02:17:02PM -0700, Andy Lutomirski wrote: > A virtqueue is a coherent DMA mapping. Use the DMA API for it. > This fixes virtio_pci on Xen. > > Signed-off-by: Andy Lutomirski > --- > drivers/virtio/virtio_pci.c | 25 ++++++++++++++++++------- > 1 file changed, 18 insertions(+), 7 deletions(-) > > diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c > index 3d1463c6b120..19039c5bec24 100644 > --- a/drivers/virtio/virtio_pci.c > +++ b/drivers/virtio/virtio_pci.c > @@ -80,8 +80,9 @@ struct virtio_pci_vq_info > /* the number of entries in the queue */ > int num; > > - /* the virtual address of the ring queue */ > - void *queue; > + /* the ring queue */ > + void *queue; /* virtual address */ > + dma_addr_t queue_dma_addr; /* bus address */ > > /* the list node for the virtqueues list */ > struct list_head node; > @@ -417,15 +418,16 @@ static struct virtqueue *setup_vq(struct virtio_device *vdev, unsigned index, > info->num = num; > info->msix_vector = msix_vec; > > - size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN)); > - info->queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO); > + size = vring_size(num, VIRTIO_PCI_VRING_ALIGN); > + info->queue = dma_zalloc_coherent(vdev->dev.parent, size, > + &info->queue_dma_addr, GFP_KERNEL); > if (info->queue == NULL) { > err = -ENOMEM; > goto out_info; > } > > /* activate the queue */ > - iowrite32(virt_to_phys(info->queue) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT, > + iowrite32(info->queue_dma_addr >> VIRTIO_PCI_QUEUE_ADDR_SHIFT, > vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN); > > /* create the vring */ > @@ -462,7 +464,8 @@ out_assign: > vring_del_virtqueue(vq); > out_activate_queue: > iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN); > - free_pages_exact(info->queue, size); > + dma_free_coherent(vdev->dev.parent, size, > + info->queue, info->queue_dma_addr); > out_info: > kfree(info); > return ERR_PTR(err); > @@ -493,7 +496,8 @@ static void vp_del_vq(struct virtqueue *vq) > iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN); > > size = PAGE_ALIGN(vring_size(info->num, VIRTIO_PCI_VRING_ALIGN)); > - free_pages_exact(info->queue, size); > + dma_free_coherent(vq->vdev->dev.parent, size, > + info->queue, info->queue_dma_addr); > kfree(info); > } > > @@ -712,6 +716,13 @@ static int virtio_pci_probe(struct pci_dev *pci_dev, > if (err) > goto out; > > + /* > + * We support 64-bit DMA. If this fails (e.g. some bridge > + * or PV code doesn't or DAC is disabled), then we're okay > + * with 32-bit DMA. I am having a hard time parsing that. Could you expand a bit the faulting use-case please? > + */ > + dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64)); The usual process is: ret = dma_set_mask_and_coherent(..) if (ret) ret = dma_set_mask_and_coherent(.., DMA_BIT_MASK(32)) if (ret) pr_warn("We are truly screwed. Good luck!\n"); > + > err = pci_request_regions(pci_dev, "virtio-pci"); > if (err) > goto out_enable_device; > -- > 1.9.3 >