Cornelia Huck
2019-Apr-09 15:47 UTC
[RFC PATCH 02/12] virtio/s390: DMA support for virtio-ccw
On Tue, 9 Apr 2019 15:23:13 +0200 Halil Pasic <pasic at linux.ibm.com> wrote:> On Tue, 9 Apr 2019 15:01:20 +0200 > Cornelia Huck <cohuck at redhat.com> wrote: > > > On Tue, 9 Apr 2019 13:29:27 +0200 > > Halil Pasic <pasic at linux.ibm.com> wrote: > > > > > On Tue, 9 Apr 2019 11:57:43 +0200 > > > Cornelia Huck <cohuck at redhat.com> wrote: > > > > > > > On Fri, 5 Apr 2019 01:16:12 +0200 > > > > Halil Pasic <pasic at linux.ibm.com> wrote:> > > > > @@ -1255,6 +1254,18 @@ static int virtio_ccw_online(struct ccw_device *cdev) > > > > > ret = -ENOMEM; > > > > > goto out_free; > > > > > } > > > > > + vcdev->vdev.dev.parent = &cdev->dev; > > > > > > > > That one makes sense, pci and mmio are doing that as well. > > > > > > > > > + cdev->dev.dma_mask = &vcdev->dma_mask; > > > > > > > > That one feels a bit weird. Will this change in one of the follow-on > > > > patches? (Have not yet looked at the whole series.) > > > > > > I don't thinks so. Do you mean this should happen within the cio code? > > > I think I started out with the idea to keep the scope as narrow as > > > possible. Do you have any suggestions? > > > > From what I see, you set the mask from the virtio-ccw side, then > > propagate it up to the general ccw_device, and then the generic virtio > > code will fetch it from the ccw_device. > > Right! For some reason dma_mask is a pointer. And I need virtio core to > use a sane value for virtio_ccw devices. > > > Don't you potentially need > > something for other ccw_devices in that protected hipervisor case as > > well (e.g for 3270)? > > > Maybe, maybe not. The first stage is likely to be virito only. I would > prefer sorting out stuff like 3270 as the need arises. Also see my > response to patch 4 (Message-Id: <20190409141114.7dcce94a at oc2783563651>).As long as the infrastructure is flexible enough to be extended later, ok. I still need to read that mail.> > > > > > > > > > > > > > > + > > > > > + ret = dma_set_mask_and_coherent(&cdev->dev, > > > > > DMA_BIT_MASK(64)); > > > > > + if (ret) > > > > > + ret = dma_set_mask_and_coherent(&cdev->dev, > > > > > + > > > > > DMA_BIT_MASK(32)); > > > > > + if (ret) { > > > > > + dev_warn(&cdev->dev, "Failed to enable 64-bit > > > > > or 32-bit DMA. Trying to continue, but this might not > > > > > work.\n"); > > > > > > > > This does not look like you'd try to continue? > > > > > > > > > > I remember now. First I did continue, then I changed this to fail > > > hard so I can not ignore any such problems while smoke testing ('I > > > don't always check the kernel messages'), but kept the old message. > > > This basically should not fail anyway, otherwise we have a problem > > > AFAIU. > > > > > > By the way virtio-pci tries to continue indeed, and this is also > > > where the wording comes from ;). > > > > > > What would you prefer? Try to continue or fail right away? > > > > If it does not have a chance of working properly in the general case, > > I'd fail. > > > > Agreed! I will make it so. Would dropping ' Trying to continue, but > this might not work.' from the warning message work for you?Sounds fine.> > I could also drop the attempt to set a 32 bit mask if you agree. Do you?Only if you also drop it from the message as well ;) Not sure in what cases you'll fail to set a 64 bit mask, but succeed with a 32 bit mask. If there's no sensible situation where that might happen, I'd just go ahead and drop it.