From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Lendacky, Thomas" Subject: Re: [PATCH 4/5] virtio: Introduce virtio_max_dma_size() Date: Wed, 30 Jan 2019 15:10:29 +0000 Message-ID: References: <20190129084342.26030-1-joro@8bytes.org> <20190129084342.26030-5-joro@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190129084342.26030-5-joro@8bytes.org> Content-Language: en-US Content-ID: 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 To: Joerg Roedel , "Michael S . Tsirkin" , Jason Wang , Konrad Rzeszutek Wilk , Christoph Hellwig Cc: Jens Axboe , "jroedel@suse.de" , "Singh, Brijesh" , "Grimm, Jon" , "jfehlig@suse.com" , "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "virtualization@lists.linux-foundation.org" List-Id: virtualization@lists.linuxfoundation.org On 1/29/19 2:43 AM, Joerg Roedel wrote: > From: Joerg Roedel > > This function returns the maximum segment size for a single > dma transaction of a virtio device. The possible limit comes > from the SWIOTLB implementation in the Linux kernel, that > has an upper limit of (currently) 256kb of contiguous > memory it can map. Other DMA-API implementations might also > have limits. > > Use the new dma_max_mapping_size() function to determine the > maximum mapping size when DMA-API is in use for virtio. > > Reviewed-by: Konrad Rzeszutek Wilk > Signed-off-by: Joerg Roedel > --- > drivers/virtio/virtio_ring.c | 10 ++++++++++ > include/linux/virtio.h | 2 ++ > 2 files changed, 12 insertions(+) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index cd7e755484e3..9ca3fe6af9fa 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -266,6 +266,16 @@ static bool vring_use_dma_api(struct virtio_device *vdev) > return false; > } > > +size_t virtio_max_dma_size(struct virtio_device *vdev) > +{ > + size_t max_segment_size = SIZE_MAX; > + > + if (vring_use_dma_api(vdev)) > + max_segment_size = dma_max_mapping_size(&vdev->dev); > + > + return max_segment_size; > +} When I build with these patches and with the virtio devices as modules I get a build failure. Looks like this needs an EXPORT_SYMBOL_GPL(). Thanks, Tom > + > static void *vring_alloc_queue(struct virtio_device *vdev, size_t size, > dma_addr_t *dma_handle, gfp_t flag) > { > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > index fa1b5da2804e..673fe3ef3607 100644 > --- a/include/linux/virtio.h > +++ b/include/linux/virtio.h > @@ -157,6 +157,8 @@ int virtio_device_freeze(struct virtio_device *dev); > int virtio_device_restore(struct virtio_device *dev); > #endif > > +size_t virtio_max_dma_size(struct virtio_device *vdev); > + > #define virtio_device_for_each_vq(vdev, vq) \ > list_for_each_entry(vq, &vdev->vqs, list) > >