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Re: [Qemu-devel] [PATCH v2 3/4] virtio-ccw: use ccw data stream
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH v2 3/4] virtio-ccw: use ccw data stream |
Date: |
Tue, 19 Sep 2017 11:06:31 +0200 |
On Tue, 19 Sep 2017 11:37:30 +0800
Dong Jia Shi <address@hidden> wrote:
> * Halil Pasic <address@hidden> [2017-09-13 13:50:28 +0200]:
>
> > Replace direct access which implicitly assumes no IDA
> > or MIDA with the new ccw data stream interface which should
> > cope with these transparently in the future.
> >
> > Signed-off-by: Halil Pasic <address@hidden>
> >
> > ---
> >
> > v1 --> v2:
> > Removed todo comments on possible errno change as with
> > https://lists.nongnu.org/archive/html/qemu-devel/2017-09/msg02441.html
> > applied it does not matter any more.
> >
> > Error handling: At the moment we ignore errors reported
> > by stream ops to keep the change minimal. An add-on
> > patch improving on this is to be expected later.
> Add a TODO somewhere around the code as a reminder?
I expect Halil to have it on his TODO list and send a patch later ;)
>
> > ---
> > hw/s390x/virtio-ccw.c | 156
> > +++++++++++++++-----------------------------------
> > 1 file changed, 46 insertions(+), 110 deletions(-)
> >
> > diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> > index b1976fdd19..a9baf6f7ab 100644
> > --- a/hw/s390x/virtio-ccw.c
> > +++ b/hw/s390x/virtio-ccw.c
> [...]
>
> > @@ -394,11 +362,8 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
> > } else {
> > VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
> >
> > - features.index = address_space_ldub(&address_space_memory,
> > - ccw.cda
> > - +
> > sizeof(features.features),
> > - MEMTXATTRS_UNSPECIFIED,
> > - NULL);
> > + ccw_dstream_advance(&sch->cds, sizeof(features.features));
> How about:
> ccw_dstream_advance(&sch->cds, offsetof(VirtioFeatDesc, index));
I think keeping sizeof(features.features) is better: It matches the old
code, and we really do jump over the features flag and revisit it
later...
>
> > + ccw_dstream_read(&sch->cds, features.index);
> > if (features.index == 0) {
> > if (dev->revision >= 1) {
> > /* Don't offer legacy features for modern devices. */
> > @@ -417,9 +382,9 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
> > /* Return zeroes if the guest supports more feature bits.
> > */
> > features.features = 0;
> > }
> > - address_space_stl_le(&address_space_memory, ccw.cda,
> > - features.features, MEMTXATTRS_UNSPECIFIED,
> > - NULL);
> > + ccw_dstream_rewind(&sch->cds);
> > + cpu_to_le32s(&features.features);
> > + ccw_dstream_write(&sch->cds, features.features);
> > sch->curr_status.scsw.count = ccw.count - sizeof(features);
> How about:
> sch->curr_status.scsw.count = ccw_dstream_residual_count(&sch->cds);
Hm, I thought I had commented on this, but I seem to have missed
these...
I'd prefer to do it as a follow-up patch.
>
> This also applies to other places.
>
> > ret = 0;
> > }
> [...]
>
> > @@ -501,21 +459,13 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
> > }
> > }
> > len = MIN(ccw.count, vdev->config_len);
> > - hw_len = len;
> > if (!ccw.cda) {
> > ret = -EFAULT;
> > } else {
> > - config = cpu_physical_memory_map(ccw.cda, &hw_len, 0);
> > - if (!config) {
> > - ret = -EFAULT;
> > - } else {
> > - len = hw_len;
> > - /* XXX config space endianness */
> > - memcpy(vdev->config, config, len);
> > - cpu_physical_memory_unmap(config, hw_len, 0, hw_len);
> > + ret = ccw_dstream_read_buf(&sch->cds, vdev->config, len);
> > + if (!ret) {
> Add a TODO here, and:
>
> if (ccw_dstream_read_buf(&sch->cds, vdev->config, len)) {
> ret = -EFAULT;
> } else {
> ....
> }
I don't think that would be correct: The function will (at least
currently) return 0 or -EINVAL, and you are now mapping any error to
-EFAULT? (Not that it has an effect in the end: We map both to a
channel program check as of "s390x/css: drop data-check in
interpretation".)
>
> > virtio_bus_set_vdev_config(&dev->bus, vdev->config);
> > sch->curr_status.scsw.count = ccw.count - len;
> > - ret = 0;
> > }
> > }
> > break;
> [...]
>
> > @@ -714,13 +654,9 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
> > ret = -EFAULT;
> > break;
> > }
> > - revinfo.revision =
> > - address_space_lduw_be(&address_space_memory, ccw.cda,
> > - MEMTXATTRS_UNSPECIFIED, NULL);
> > - revinfo.length =
> > - address_space_lduw_be(&address_space_memory,
> > - ccw.cda + sizeof(revinfo.revision),
> > - MEMTXATTRS_UNSPECIFIED, NULL);
> > + ccw_dstream_read_buf(&sch->cds, &revinfo, 4);
> ^
> A magic number? O:)
Hah :)
We can't use sizeof(revinfo), and sizeof(revinfo.revision) +
sizeof(revinfo.length) is a bit unwieldy. Let's keep some magic in our
code :)
>
> > + be16_to_cpus(&revinfo.revision);
> > + be16_to_cpus(&revinfo.length);
> > if (ccw.count < len + revinfo.length ||
> > (check_len && ccw.count > len + revinfo.length)) {
> > ret = -EINVAL;
> > --
> > 2.13.5
> >
>
> Otherwise, looks good.
>
Can I get an ack?
- Re: [Qemu-devel] [PATCH v2 1/4] s390x/css: introduce css data stream, (continued)
[Qemu-devel] [PATCH v2 3/4] virtio-ccw: use ccw data stream, Halil Pasic, 2017/09/13
Re: [Qemu-devel] [PATCH v2 3/4] virtio-ccw: use ccw data stream, Pierre Morel, 2017/09/19
Re: [Qemu-devel] [PATCH v2 0/4] add CCW indirect data access support, Cornelia Huck, 2017/09/14
Re: [Qemu-devel] [PATCH v2 0/4] add CCW indirect data access support, Cornelia Huck, 2017/09/14