On Tue, 22 Jan 2019, hch@xxxxxxxxxxxxx wrote: > On Tue, Jan 22, 2019 at 11:59:31AM -0800, Stefano Stabellini wrote: > > > if (!virtio_has_iommu_quirk(vdev)) > > > return true; > > > > > > @@ -260,7 +262,7 @@ static bool vring_use_dma_api(struct virtio_device *vdev) > > > * the DMA API if we're a Xen guest, which at least allows > > > * all of the sensible Xen configurations to work correctly. > > > */ > > > - if (xen_domain()) > > > + if (xen_domain() && !dma_dev->dma_mem) > > > return true; > > > > > > return false; > > > > I can see you spotted a real issue, but this is not the right fix. We > > just need something a bit more flexible than xen_domain(): there are > > many kinds of Xen domains on different architectures, we basically want > > to enable this (return true from vring_use_dma_api) only when the xen > > swiotlb is meant to be used. Does the appended patch fix the issue you > > have? > > The problem generally is the other way around - if dma_dev->dma_mem > is set the device decription in the device tree explicitly requires > using this memory, so we must _always_ use the DMA API. > > The problem is just that that rproc driver absuses the DMA API > in horrible ways. If vring_use_dma_api is actually supposed to return true when dma_dev->dma_mem is set, then both Peng's patch and the patch I wrote are not fixing the real issue here. I don't know enough about remoteproc to know where the problem actually lies though.
