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Re: [Qemu-devel] [PATCH 4/9] s390x: refactor error handling for SSCH and
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH 4/9] s390x: refactor error handling for SSCH and RSCH |
Date: |
Thu, 31 Aug 2017 11:55:35 +0200 |
On Wed, 30 Aug 2017 18:36:04 +0200
Halil Pasic <address@hidden> wrote:
> Simplify the error handling of the SSCH and RSCH handler avoiding
> arbitrary and cryptic error codes being mapped to what a subchannel is
> supposed to do. Let the code detecting the condition tell how it's to be
> handled in a less ambiguous way. It's best to handle SSCH and RSCH in
> one go as the emulation of the two shares a lot of code.
So determining the return code at the point in time where we can
instead of trying to map to return codes and back again makes quite a
bit of sense, but I'll have to look at the rest of this. For one thing,
would a better split to introduce the cc-reporting infrastructure first
and then convert the different I/O functions?
>
> Signed-off-by: Halil Pasic <address@hidden>
> Acked-by: Pierre Morel<address@hidden>
>
> ---
> Notes:
> Funny, we had a different swich-case for SSCH and RSCH. For
> virtual it did not matter, but for passtrough it could. In practice
> -EINVAL from the kernel would have been mapped to cc 2 in case of
> RSCH and to cc 1 in case of SSHC which is absurd. Same goes for
> -EBUSY from kernel which is correctly mapped to cc 2 in case of
> SSCH, but for RSCH it gets mapped to cc 1 which is also absurd.
> ---
> hw/s390x/css.c | 86
> ++++++++++++++-------------------------------
> hw/s390x/s390-ccw.c | 8 ++---
> hw/vfio/ccw.c | 32 +++++++++++++----
> include/hw/s390x/css.h | 30 ++++++++++++----
> include/hw/s390x/s390-ccw.h | 2 +-
> target/s390x/ioinst.c | 61 +++++++++-----------------------
> 6 files changed, 97 insertions(+), 122 deletions(-)
>
> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> index bc47bf5b20..1102642c10 100644
> --- a/hw/s390x/css.c
> +++ b/hw/s390x/css.c
> @@ -1015,12 +1015,11 @@ static void sch_handle_start_func_virtual(SubchDev
> *sch)
>
> }
>
> -static int sch_handle_start_func_passthrough(SubchDev *sch)
> +static void sch_handle_start_func_passthrough(SubchDev *sch)
> {
>
> PMCW *p = &sch->curr_status.pmcw;
> SCSW *s = &sch->curr_status.scsw;
> - int ret;
>
> ORB *orb = &sch->orb;
> if (!(s->ctrl & SCSW_ACTL_SUSP)) {
> @@ -1034,28 +1033,10 @@ static int sch_handle_start_func_passthrough(SubchDev
> *sch)
> */
> if (!(orb->ctrl0 & ORB_CTRL0_MASK_PFCH) ||
> !(orb->ctrl0 & ORB_CTRL0_MASK_C64)) {
> - return -ENODEV;
> + sch->iret.cc = 3;
Same as already commented: I don't think cc 3 is a good match.
> }
>
> - ret = s390_ccw_cmd_request(orb, s, sch->driver_data);
> - switch (ret) {
> - /* Currently we don't update control block and just return the cc code.
> */
> - case 0:
> - break;
> - case -EBUSY:
> - break;
> - case -ENODEV:
> - break;
> - case -EFAULT:
> - break;
> - case -EACCES:
> - /* Let's reflect an inaccessible host device by cc 3. */
> - default:
> - /* Let's make all other return codes map to cc 3. */
> - ret = -ENODEV;
> - };
> -
> - return ret;
> + s390_ccw_cmd_request(sch);
As you change the handling anyway: Don't change this logic in prior
patches?
> }
>
> /*
> @@ -1064,7 +1045,7 @@ static int sch_handle_start_func_passthrough(SubchDev
> *sch)
> * read/writes) asynchronous later on if we start supporting more than
> * our current very simple devices.
> */
> -int do_subchannel_work_virtual(SubchDev *sch)
> +void do_subchannel_work_virtual(SubchDev *sch)
> {
>
> SCSW *s = &sch->curr_status.scsw;
> @@ -1078,41 +1059,35 @@ int do_subchannel_work_virtual(SubchDev *sch)
> sch_handle_start_func_virtual(sch);
> } else {
> /* Cannot happen. */
> - return -ENODEV;
> + sch->iret.cc = 3;
See comment for the last patch.
> }
> css_inject_io_interrupt(sch);
> - return 0;
> }
>
> -int do_subchannel_work_passthrough(SubchDev *sch)
> +void do_subchannel_work_passthrough(SubchDev *sch)
> {
> - int ret;
> SCSW *s = &sch->curr_status.scsw;
>
> if (s->ctrl & SCSW_FCTL_CLEAR_FUNC) {
> /* TODO: Clear handling */
> sch_handle_clear_func(sch);
> - ret = 0;
> } else if (s->ctrl & SCSW_FCTL_HALT_FUNC) {
> /* TODO: Halt handling */
> sch_handle_halt_func(sch);
> - ret = 0;
> } else if (s->ctrl & SCSW_FCTL_START_FUNC) {
> - ret = sch_handle_start_func_passthrough(sch);
> + sch_handle_start_func_passthrough(sch);
> } else {
> /* Cannot happen. */
> - return -ENODEV;
> + sch->iret.cc = 3;
ftcl == 0 should have been rejected already by the function handlers
here as well, shouldn't it?
> }
> -
> - return ret;
> }
>
> -static int do_subchannel_work(SubchDev *sch)
> +static void do_subchannel_work(SubchDev *sch)
> {
> if (sch->do_subchannel_work) {
> - return sch->do_subchannel_work(sch);
> + sch->do_subchannel_work(sch);
> } else {
> - return -ENODEV;
> + sch->iret.cc = 3;
See my comment for a prior patch.
> }
> }
>
(...)
> diff --git a/include/hw/s390x/css.h b/include/hw/s390x/css.h
> index 5c5fe6b202..d093181a9e 100644
> --- a/include/hw/s390x/css.h
> +++ b/include/hw/s390x/css.h
> @@ -94,13 +94,31 @@ struct SubchDev {
> /* transport-provided data: */
> int (*ccw_cb) (SubchDev *, CCW1);
> void (*disable_cb)(SubchDev *);
> - int (*do_subchannel_work) (SubchDev *);
> + void (*do_subchannel_work) (SubchDev *);
> SenseId id;
> void *driver_data;
> + /* io instructions conclude according to iret */
> + struct {
> + /*
> + * General semantic of cc codes of IO instructions is (brief):
> + * 0 -- produced expected result
> + * 1 -- produced alternate result
> + * 2 -- ineffective, because busy with previously initiated function
> + * 3 -- ineffective, not operational
I'm not sure you can summarize this that way in all cases.
Also, what does "ineffective" mean? If I get a cc 1 for, say, ssch, I
don't expect something either as the subchannel was already status
pending.
> + */
> + uint32_t cc:4;
> + bool pgm_chk:1;
This looks weird?
> + uint32_t irq_code;
> + } iret;
> };
>
> extern const VMStateDescription vmstate_subch_dev;
(...)
> @@ -238,33 +236,17 @@ void ioinst_handle_ssch(S390CPU *cpu, uint64_t reg1,
> uint32_t ipb)
> }
> trace_ioinst_sch_id("ssch", cssid, ssid, schid);
> sch = css_find_subch(m, cssid, ssid, schid);
> - if (sch && css_subch_visible(sch)) {
> - ret = css_do_ssch(sch, &orb);
> + if (!sch || !css_subch_visible(sch)) {
> + setcc(cpu, 3);
> + return;
> }
> - switch (ret) {
> - case -ENODEV:
> - cc = 3;
> - break;
> - case -EBUSY:
> - cc = 2;
> - break;
> - case -EFAULT:
> - /*
> - * TODO:
> - * I'm wondering whether there is something better
> - * to do for us here (like setting some device or
> - * subchannel status).
> - */
You removed the TODO :(
There still might be a better way to reflect this...
> - program_interrupt(env, PGM_ADDRESSING, 4);
> + css_subch_clear_iret(sch);
> + css_do_ssch(sch, &orb);
> + if (sch->iret.pgm_chk) {
> + program_interrupt(env, sch->iret.irq_code, 4);
> return;
> - case 0:
> - cc = 0;
> - break;
> - default:
> - cc = 1;
> - break;
> }
> - setcc(cpu, cc);
> + setcc(cpu, sch->iret.cc);
> }
>
> void ioinst_handle_stcrw(S390CPU *cpu, uint32_t ipb)
- [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, (continued)
- [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
- [Qemu-devel] [PATCH 6/9] s390x: refactor error handling for CSCH handler, Halil Pasic, 2017/08/30
- [Qemu-devel] [PATCH 4/9] s390x: refactor error handling for SSCH and RSCH, Halil Pasic, 2017/08/30
- Re: [Qemu-devel] [PATCH 4/9] s390x: refactor error handling for SSCH and RSCH,
Cornelia Huck <=
- [Qemu-devel] [PATCH 5/9] s390x: refactor error handling for XSCH handler, Halil Pasic, 2017/08/30
- [Qemu-devel] [PATCH 7/9] s390x: refactor error handling for HSCH handler, Halil Pasic, 2017/08/30
- [Qemu-devel] [PATCH 8/9] s390x: refactor error handling for MSCH handler, Halil Pasic, 2017/08/30
- [Qemu-devel] [PATCH 9/9] s390x: factor out common ioinst handler logic, Halil Pasic, 2017/08/30
- Re: [Qemu-devel] [PATCH 0/9], Cornelia Huck, 2017/08/31