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Re: [RFC PATCH v2 1/7] vfio-ccw: Return IOINST_CC_NOT_OPERATIONAL for EI
Re: [RFC PATCH v2 1/7] vfio-ccw: Return IOINST_CC_NOT_OPERATIONAL for EIO
Wed, 25 Mar 2020 03:24:28 +0100
On Tue, 24 Mar 2020 18:04:30 +0100
Cornelia Huck <address@hidden> wrote:
> On Thu, 6 Feb 2020 22:45:03 +0100
> Eric Farman <address@hidden> wrote:
> > From: Farhan Ali <address@hidden>
> > EIO is returned by vfio-ccw mediated device when the backing
> > host subchannel is not operational anymore. So return cc=3
> > back to the guest, rather than returning a unit check.
> > This way the guest can take appropriate action such as
> > issue an 'stsch'.
I believe this is not the only situation when vfio-ccw returns
> > Signed-off-by: Farhan Ali <address@hidden>
> > Signed-off-by: Eric Farman <address@hidden>
> > ---
> > Notes:
> > v1->v2: [EF]
> > - Add s-o-b
> > - [Seems the discussion on v1 centered on the return code
> > set in the kernel, rather than anything that needs to
> > change here, unless I've missed something.]
Does this need to change here? If the kernel is supposed to return ENODEV
then this does not need to change.
> I've stared at this and at the kernel code for some time again; and I'm
> not sure if "return -EIO == not operational" is even true. That said,
> I'm not sure a unit check is the right response, either. The only thing
> I'm sure about is that the kernel code needs some review of return
> codes and some documentation...
I could not agree more, this is semantically uapi and needs to be
With regards to "linux error codes: vs "ionist cc's" an where
the mapping is different example:
* cio_cancel_halt_clear - Cancel running I/O by performing cancel, halt
* and clear ordinally if subchannel is valid.
* @sch: subchannel on which to perform the cancel_halt_clear operation
* @iretry: the number of the times remained to retry the next operation
* This should be called repeatedly since halt/clear are asynchronous
* operations. We do one try with cio_cancel, three tries with cio_halt,
* 255 tries with cio_clear. The caller should initialize @iretry with
* the value 255 for its first call to this, and keep using the same
* @iretry in the subsequent calls until it gets a non -EBUSY return.
* Returns 0 if device now idle, -ENODEV for device not operational,
* -EBUSY if an interrupt is expected (either from halt/clear or from a
* status pending), and -EIO if out of retries.
int cio_cancel_halt_clear(struct subchannel *sch, int *iretry)
Here -ENODEV is not operational.
> > hw/vfio/ccw.c | 1 +
> > 1 file changed, 1 insertion(+)
> > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > index 50cc2ec75c..19144ecfc7 100644
> > --- a/hw/vfio/ccw.c
> > +++ b/hw/vfio/ccw.c
> > @@ -114,6 +114,7 @@ again:
> > return IOINST_CC_BUSY;
> > case -ENODEV:
> > case -EACCES:
> > + case -EIO:
> > return IOINST_CC_NOT_OPERATIONAL;
> > case -EFAULT:
> > default: