Cornelia Huck
2019-Apr-09 13:01 UTC
[RFC PATCH 02/12] virtio/s390: DMA support for virtio-ccw
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: > > > > > Currently we have a problem if a virtio-ccw device has > > > VIRTIO_F_IOMMU_PLATFORM. > > > > Can you please describe what the actual problem is? > > > > Without this patch: > > WARNING: CPU: 2 PID: 26 > at [..]/kernel/dma/mapping.c:251 > dma_alloc_attrs+0x8e/0xd0 Modules linked in: CPU: 2 PID: 26 Comm: > kworker/u6:1 Not tainted 5.1.0-rc3-00023-g1ec89ec #596 Hardware name: > IBM 2964 NC9 712 (KVM/Linux) Workqueue: events_unbound async_run_entry_fn > Krnl PSW : 0704c00180000000 000000000021b18e (dma_alloc_attrs+0x8e/0xd0) > R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3 > Krnl GPRS: 0000000000000000 0000000000000000 0000000000000000 > 0000000000001406 000003e00040f838 0000000000002dc0 0000000000000100 > 0000000000000001 0000000000001000 000000000236f028 000003e00040f838 > 0000000000001406 000000004b289828 0000000000000080 000003e00040f6f8 > 000003e00040f6a0 Krnl Code: 000000000021b17e: f0e00004ebaf > srp 4(15,%r0),2991(%r14),0 000000000021b184: f0c0000407f4 > srp 4(13,%r0),2036,0 #000000000021b18a: a7f40001 > brc 15,21b18c >000000000021b18e: ec5520bc0055 risbg > %r5,%r5,32,188,0 000000000021b194: b9020011 ltgr > %r1,%r1 000000000021b198: a784ffd9 brc 8,21b14a > 000000000021b19c: e31010000002 ltg %r1,0(%r1) > 000000000021b1a2: a7840012 brc 8,21b1c6 > Call Trace: > ([<0000000000000004>] 0x4) > [<00000000007a7d54>] vring_alloc_queue+0x74/0x90 > [<00000000007a8390>] vring_create_virtqueue+0xf8/0x288 > [<0000000000919ec0>] virtio_ccw_find_vqs+0xf8/0x950 > [<000000000080772e>] init_vq+0x16e/0x318 > [<00000000008087c4>] virtblk_probe+0xf4/0xb58 > [<00000000007a62a6>] virtio_dev_probe+0x1a6/0x250 > [<00000000007ea498>] really_probe+0x1c8/0x290 > [<00000000007ea746>] driver_probe_device+0x86/0x160 > [<00000000007e7cba>] bus_for_each_drv+0x7a/0xc0 > [<00000000007ea23c>] __device_attach+0xfc/0x180 > [<00000000007e9116>] bus_probe_device+0xae/0xc8 > [<00000000007e5066>] device_add+0x3fe/0x698 > [<00000000007a5d92>] register_virtio_device+0xca/0x120 > [<00000000009195a2>] virtio_ccw_online+0x1b2/0x220 > [<000000000089853e>] ccw_device_set_online+0x1d6/0x4d8 > [<0000000000918cf6>] virtio_ccw_auto_online+0x26/0x58 > [<00000000001a61b6>] async_run_entry_fn+0x5e/0x158 > [<0000000000199322>] process_one_work+0x25a/0x668 > [<000000000019977a>] worker_thread+0x4a/0x428 > [<00000000001a1ae8>] kthread+0x150/0x170 > [<0000000000aeab3a>] kernel_thread_starter+0x6/0xc > [<0000000000aeab34>] kernel_thread_starter+0x0/0xc > > [..] > > virtio_ccw 0.0.0301: no vq > ---[ end trace d35815958c12cad3 ]--- > virtio_ccw 0.0.0300: no vq > virtio_blk: probe of virtio1 failed with error -12 > virtio_blk: probe of virtio3 failed with error -12 > > Means virtio devices broken. > > Should I > s/we have a problem if a virtio-ccw device/virtio-ccw devices do not work if the device/ > ?Much better :) (That is, this happens if we switch on the feature bit in the hypervisor, right?)> > > > In future we do want to support DMA API with > > > virtio-ccw. > > > > > > Let us do the plumbing, so the feature VIRTIO_F_IOMMU_PLATFORM works > > > with virtio-ccw. > > > > > > Let us also switch from legacy avail/used accessors to the DMA aware > > > ones (even if it isn't strictly necessary). > > > > I think with this change we can remove the legacy accessors, if I > > didn't mis-grep. > > > > That is possible, I can do that in v1.Sounds good.> > > > > > > Signed-off-by: Halil Pasic <pasic at linux.ibm.com> > > > --- > > > drivers/s390/virtio/virtio_ccw.c | 23 +++++++++++++++++------ > > > 1 file changed, 17 insertions(+), 6 deletions(-)(...)> > > @@ -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. Don't you potentially need something for other ccw_devices in that protected hipervisor case as well (e.g for 3270)?> > > > > > + > > > + 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.> > Regards, > Halil > > > > + goto out_free; > > > + } > > > + > > > vcdev->config_block = kzalloc(sizeof(*vcdev->config_block), > > > GFP_DMA | GFP_KERNEL); > > > if (!vcdev->config_block) { > > >
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