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vfio-ccw: support hsch/csch (QEMU part)

PATCH Superseded Cornelia Huck 1 participant 3 messages Jan 21, 2019

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KVM s390

v2 of 4 Superseded Latest is v4 →

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Cornelia Huck

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#0 lore raw

v2 cover vfio-ccw: support hsch/csch (QEMU part)

[This is the QEMU part, git tree is available at
https://github.com/cohuck/qemu vfio-ccw-caps

The companion Linux kernel patches are available at
https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/vfio-ccw.git vfio-ccw-eagain-caps]

Currently, vfio-ccw only relays START SUBCHANNEL requests to the real device. This tends to work well for the most common 'good path' scenarios; however, as we emulate {HALT,CLEAR} SUBCHANNEL in QEMU, things like clearing pending requests at the device is currently not supported. This may be a problem for e.g. error recovery.

This patch series makes use of the newly introduced async command region to issue hsch/csch; if it is not present, continue to emulate hsch/csch, as before.

Note that the kernel side now returns -EAGAIN to trigger a retry in more cases; QEMU should already be fine with that.

[I'm not quite happy with how this async processing hooks up in css.c; ideas welcome.]

Lightly tested (I can interact with a dasd as before, and reserve/release seems to work well.) Not sure if there is a better way to test this, ideas welcome.

Changes v1->v2:
- update kernel header to v2 of kernel patches
- rebased on master

Cornelia Huck (2):
vfio-ccw: new capability chain support
vfio-ccw: support async command subregion

 hw/s390x/css.c                 |  27 ++++++--
 hw/vfio/ccw.c                  | 109 ++++++++++++++++++++++++++++++++-
 include/hw/s390x/s390-ccw.h    |   3 +
 linux-headers/linux/vfio.h     |   4 ++
 linux-headers/linux/vfio_ccw.h |  12 ++++
 5 files changed, 149 insertions(+), 6 deletions(-)
Signature · 1 line
2.17.2
author
#1 lore raw

PATCH v2 1/2 vfio-ccw: new capability chain support

To be replaced with a real linux-headers update.

Signed-off-by Cornelia Huck <[email protected]>
---
 linux-headers/linux/vfio.h     |  4 ++++
 linux-headers/linux/vfio_ccw.h | 12 ++++++++++++
 2 files changed, 16 insertions(+)
linux-headers/linux/vfio.h +4 -0
index ceb6453394..2965c9fbd7 100644
@@ -303,6 +303,10 @@ struct vfio_region_info_cap_type {
 #define VFIO_REGION_SUBTYPE_INTEL_IGD_HOST_CFG	(2)
 #define VFIO_REGION_SUBTYPE_INTEL_IGD_LPC_CFG	(3)
 
+#define VFIO_REGION_TYPE_CCW			(2)
+/* ccw sub-types */
+#define VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD	(1)
+
 /*
  * The MSIX mappable capability informs that MSIX data of a BAR can be mmapped
  * which allows direct access to non-MSIX registers which happened to be within
linux-headers/linux/vfio_ccw.h +12 -0
index 5bf96c3812..fcc3e69ef5 100644
@@ -12,6 +12,7 @@
 
 #include <linux/types.h>
 
+/* used for START SUBCHANNEL, always present */
 struct ccw_io_region {
 #define ORB_AREA_SIZE 12
 	__u8	orb_area[ORB_AREA_SIZE];

@@ -22,4 +23,15 @@ struct ccw_io_region {
 	__u32	ret_code;
 } __attribute__((packed));
 
+/*
+ * used for processing commands that trigger asynchronous actions
+ * Note: this is controlled by a capability
+ */
+#define VFIO_CCW_ASYNC_CMD_HSCH (1 << 0)
+#define VFIO_CCW_ASYNC_CMD_CSCH (1 << 1)
+struct ccw_cmd_region {
+	__u32 command;
+	__u32 ret_code;
+} __attribute__((packed));
+
 #endif
Signature · 1 line
2.17.2
author
#2 lore raw

PATCH v2 2/2 vfio-ccw: support async command subregion

In reply to Cornelia Huck

A vfio-ccw device may provide an async command subregion for issuing halt/clear subchannel requests. If it is present, use it for sending halt/clear request to the device; if not, fall back to emulation (as done today).

Signed-off-by Cornelia Huck <[email protected]>
---
 hw/s390x/css.c              |  27 +++++++--
 hw/vfio/ccw.c               | 109 +++++++++++++++++++++++++++++++++++-
 include/hw/s390x/s390-ccw.h |   3 +
 3 files changed, 133 insertions(+), 6 deletions(-)
hw/s390x/css.c +23 -4
index f92b046cd3..32e6980496 100644
@@ -22,6 +22,7 @@
 #include "trace.h"
 #include "hw/s390x/s390_flic.h"
 #include "hw/s390x/s390-virtio-ccw.h"
+#include "hw/s390x/s390-ccw.h"
 
 typedef struct CrwContainer {
     CRW crw;

@@ -1194,6 +1195,26 @@ static void sch_handle_start_func_virtual(SubchDev *sch)
 
 }
 
+static void sch_handle_halt_func_passthrough(SubchDev *sch)
+{
+    int ret;
+
+    ret = vfio_ccw_handle_halt(sch);
+    if (ret == -ENOSYS) {
+        sch_handle_halt_func(sch);
+    }
+}
+
+static void sch_handle_clear_func_passthrough(SubchDev *sch)
+{
+    int ret;
+
+    ret = vfio_ccw_handle_clear(sch);
+    if (ret == -ENOSYS) {
+        sch_handle_clear_func(sch);
+    }
+}
+
 static IOInstEnding sch_handle_start_func_passthrough(SubchDev *sch)
 {
 

@@ -1237,11 +1258,9 @@ IOInstEnding do_subchannel_work_passthrough(SubchDev *sch)
     SCSW *s = &sch->curr_status.scsw;
 
     if (s->ctrl & SCSW_FCTL_CLEAR_FUNC) {
-        /* TODO: Clear handling */
-        sch_handle_clear_func(sch);
+        sch_handle_clear_func_passthrough(sch);
     } else if (s->ctrl & SCSW_FCTL_HALT_FUNC) {
-        /* TODO: Halt handling */
-        sch_handle_halt_func(sch);
+        sch_handle_halt_func_passthrough(sch);
     } else if (s->ctrl & SCSW_FCTL_START_FUNC) {
         return sch_handle_start_func_passthrough(sch);
     }
hw/vfio/ccw.c +107 -2

143 lines not on this page · raw message

include/hw/s390x/s390-ccw.h +3 -0
index 7d15a1a5d4..38d54a7a69 100644
@@ -36,4 +36,7 @@ typedef struct S390CCWDeviceClass {
     IOInstEnding (*handle_request) (SubchDev *sch);
 } S390CCWDeviceClass;
 
+int vfio_ccw_handle_clear(SubchDev *sch);
+int vfio_ccw_handle_halt(SubchDev *sch);
+
 #endif
Signature · 1 line
2.17.2