[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 1/9] s390x/css: fix cc handling for XSCH
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH 1/9] s390x/css: fix cc handling for XSCH |
Date: |
Thu, 31 Aug 2017 10:42:43 +0200 |
On Thu, 31 Aug 2017 09:32:49 +0200
Thomas Huth <address@hidden> wrote:
> On 31.08.2017 08:38, Cornelia Huck wrote:
> > On Thu, 31 Aug 2017 07:51:17 +0200
> > Thomas Huth <address@hidden> wrote:
> >
> >> On 30.08.2017 18:36, Halil Pasic wrote:
> >>> The function ioinst_handle_xsch is presenting cc 2 when it's supposed to
> >>> present cc 1 and the other way around, because css_do_xsch has the error
> >>> codes mixed up. Fixing the error codes also fixes the priority.
> >>>
> >>> Let us fix this.
> >>
> >> (Nit: In case you respin, I'd suggest to remove the last sentence. You
> >> already used "fix" two times in the previous one)
> >
> > I can also remove it on applying, if Halil agrees (I have not yet
> > reviewed it, though).
> >
> >>
> >>> Signed-off-by: Halil Pasic <address@hidden>
> >>> Reported-by: Pierre Morel<address@hidden>
> >>
> >> Space missing -------------^
> >
> > And I can also add that space on applying :)
> >
> >>
> >>> ---
> >>> hw/s390x/css.c | 4 ++--
> >>> 1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> >>> index 1880b1a0ff..a50fb0727e 100644
> >>> --- a/hw/s390x/css.c
> >>> +++ b/hw/s390x/css.c
> >>> @@ -1281,12 +1281,12 @@ int css_do_xsch(SubchDev *sch)
> >>> (!(s->ctrl &
> >>> (SCSW_ACTL_RESUME_PEND | SCSW_ACTL_START_PEND |
> >>> SCSW_ACTL_SUSP))) ||
> >>> (s->ctrl & SCSW_ACTL_SUBCH_ACTIVE)) {
> >>> - ret = -EINPROGRESS;
> >>> + ret = -EBUSY;
> >>> goto out;
> >>> }
> >>>
> >>> if (s->ctrl & SCSW_CTRL_MASK_STCTL) {
> >>> - ret = -EBUSY;
> >>> + ret = -EINPROGRESS;
> >>> goto out;
> >>> }
> >>
> >> Using both, EBUSY and EINPROGRESS as error codes sounds very confusing
> >> to me here ... what's the difference between busy and in-progress? So
> >> while you're at it, maybe you could replace the code for CC 2 ("CANCEL
> >> SUBCHANNEL not applicable") with a different error code?
> >
> > IIRC, I used these two as they matched my idea of what happens best
> > (there's a difference between "subchannel is busy" and "the I/O is
> > already in progress, too late to cancel"). "xsch not applicable" is
> > very hard to translate to an Unix error code :/
>
> OK, the codes make more sense with your description ==> Maybe simply add
> a proper comment for each of the return codes?
Taking a step back and looking at the other I/O instructions and their
implementation in qemu:
- For those instructions that can set it, cc 1 is set when the
subchannel is status pending. That's usually the "default" branch in
ioinst.c.
- cc 2 is set when the subchannel is "busy" (or, in the case of xsch,
"not applicable for xsch"... sigh) This is supposed to be handled via
-EBUSY.
So, there are actually two problems with the current implementation of
xsch:
- The return codes are switched around, which this patch fixes.
- But "status pending" should also take precedence over "not
applicable", if I read the PoP correctly, so the second if needs to
be moved up.
And yes, it makes sense do add some comments...
[Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Halil Pasic, 2017/08/30
[Qemu-devel] [PATCH 3/9] s390x/css: be more consistent if broken beyond repair, Halil Pasic, 2017/08/30