Re: [PATCH RFC 1/2] vfio-ccw: forward halt/clear to device if supported
From: Pierre Morel
Date: Wed May 16 2018 - 09:21:19 EST
On 15/05/2018 18:01, Cornelia Huck wrote:
On Fri, 11 May 2018 11:53:52 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
On 09/05/2018 17:49, Cornelia Huck wrote:
The initial version of vfio-ccw did not support forwarding of the
halt or clear functions to the device, and we had to emulate them
instead.
For versions of the vfio-ccw kernel implementation that indeed do
support halt/clear (by indicating them in the fctl of the scsw in
the io_region), we can simply start making use of it. If the kernel
does not support handling halt/clear, fall back to emulation.
Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
---
hw/s390x/css.c | 32 ++++++++++++++++++++++++++++----
hw/vfio/ccw.c | 11 +++++++++--
include/hw/s390x/css.h | 10 +++++++---
3 files changed, 44 insertions(+), 9 deletions(-)
diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 301bf1772f..b6727d0607 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -1180,6 +1180,16 @@ static void sch_handle_start_func_virtual(SubchDev *sch)
}
+static IOInstEnding sch_handle_clear_func_passthrough(SubchDev *sch)
+{
+ return s390_ccw_cmd_request(sch);
+}
+
+static IOInstEnding sch_handle_halt_func_passthrough(SubchDev *sch)
+{
+ return s390_ccw_cmd_request(sch);
+}
+
static IOInstEnding sch_handle_start_func_passthrough(SubchDev *sch)
{
@@ -1233,13 +1243,27 @@ IOInstEnding do_subchannel_work_virtual(SubchDev *sch)
IOInstEnding do_subchannel_work_passthrough(SubchDev *sch)
{
SCSW *s = &sch->curr_status.scsw;
+ static bool no_halt_clear;
+ /* if the kernel does not support halt/clear, fall back to emulation */
if (s->ctrl & SCSW_FCTL_CLEAR_FUNC) {
- /* TODO: Clear handling */
- sch_handle_clear_func(sch);
+ if (no_halt_clear) {
+ sch_handle_clear_func(sch);
+ } else {
+ if (sch_handle_clear_func_passthrough(sch) == IOINST_OPNOTSUPP) {
+ no_halt_clear = true;
+ sch_handle_halt_func(sch);
+ }
+ }
} else if (s->ctrl & SCSW_FCTL_HALT_FUNC) {
- /* TODO: Halt handling */
- sch_handle_halt_func(sch);
+ if (no_halt_clear) {
+ sch_handle_halt_func(sch);
+ } else {
+ if (sch_handle_halt_func_passthrough(sch) == IOINST_OPNOTSUPP) {
+ no_halt_clear = true;
+ sch_handle_halt_func(sch);
+ }
+ }
} else if (s->ctrl & SCSW_FCTL_START_FUNC) {
return sch_handle_start_func_passthrough(sch);
}
diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
index e67392c5f9..247901ae41 100644
--- a/hw/vfio/ccw.c
+++ b/hw/vfio/ccw.c
@@ -60,6 +60,7 @@ static IOInstEnding vfio_ccw_handle_request(SubchDev *sch)
memset(region, 0, sizeof(*region));
+ /* orb is only valid for ssch, but does not hurt for other functions */
memcpy(region->orb_area, &sch->orb, sizeof(ORB));
memcpy(region->scsw_area, &sch->curr_status.scsw, sizeof(SCSW));
@@ -70,8 +71,12 @@ again:
if (errno == EAGAIN) {
goto again;
}
- error_report("vfio-ccw: wirte I/O region failed with errno=%d", errno);
- ret = -errno;
+ /* handle not supported operations like halt/clear on older kernels */
+ if (ret != -EOPNOTSUPP) {
+ error_report("vfio-ccw: write I/O region failed with errno=%d",
+ errno);
+ ret = -errno;
+ }
} else {
ret = region->ret_code;
}
@@ -83,6 +88,8 @@ again:
case -ENODEV:
case -EACCES:
return IOINST_CC_NOT_OPERATIONAL;
+ case -EOPNOTSUPP:
+ return IOINST_OPNOTSUPP;
case -EFAULT:
default:
sch_gen_unit_exception(sch);
diff --git a/include/hw/s390x/css.h b/include/hw/s390x/css.h
index 35facb47d2..e33f26882b 100644
--- a/include/hw/s390x/css.h
+++ b/include/hw/s390x/css.h
@@ -100,9 +100,11 @@ typedef struct CcwDataStream {
} CcwDataStream;
/*
- * IO instructions conclude according to this. Currently we have only
- * cc codes. Valid values are 0, 1, 2, 3 and the generic semantic for
+ * IO instructions conclude according to this. One class of values are
+ * cc codes: Valid values are 0, 1, 2, 3 and the generic semantic for
* IO instructions is described briefly. For more details consult the PoP.
+ * Additionally, other endings may occur due to internal processing errors
+ * like lack of support for an operation.
*/
typedef enum IOInstEnding {
/* produced expected result */
@@ -112,7 +114,9 @@ typedef enum IOInstEnding {
/* inst. ineffective because busy with previously initiated function */
IOINST_CC_BUSY = 2,
/* inst. ineffective because not operational */
- IOINST_CC_NOT_OPERATIONAL = 3
+ IOINST_CC_NOT_OPERATIONAL = 3,
+ /* internal: operation not supported */
+ IOINST_OPNOTSUPP = 4
} IOInstEnding;
typedef struct SubchDev SubchDev;
Couldn't we introduce ABI versioning ?
Can you elaborate what you're referring to?
If you mean checking capabilities of the kernel or so: If we can avoid
that and just try (and stop if it does not work), I'd prefer that (no
dependencies).
VFIO_CHECK_EXTENSION is already used in different drivers
for this kind of interface extension.
We could use it to setup appropriate callbacks for scsh/csch/xsch/hsch
depending on the extension argument.
The IOINST_OPNOTSUPP is a bit ugly, but I did not see a more elegant
way to pass 'not supported' up to the caller.
--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany