[Qemu-devel] [RFC 01/12] vfio: Start improving VFIO/EEH interface

[David Gibson <david@gibson.dropbear.id.au>]

At present the code handling IBM's Enhanced Error Handling (EEH) interface
on VFIO devices operates by bypassing the usual VFIO logic with
vfio_container_ioctl().  That's a poorly designed interface with unclear
semantics about exactly what can be operated on.

In particular it operates on a single vfio container internally (hence the
name), but takes an address space and group id, from which it deduces the
container in a rather roundabout way.  groupids are something that code
outside vfio shouldn't even be aware of.

This patch creates new interfaces for EEH operations.  Internally we
have vfio_eeh_container_op() which takes a VFIOContainer object
directly.  For external use we have vfio_eeh_as_ok() which determines
if an AddressSpace is usable for EEH (at present this means it has a
single container and at most a single group attached), and
vfio_eeh_as_op() which will perform an operation on an AddressSpace in
the unambiguous case, and otherwise returns an error.

This interface still isn't great, but it's enough of an improvement to
allow a number of cleanups in other places.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/vfio/common.c       | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/hw/vfio/vfio.h |  2 ++
 2 files changed, 79 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 6797208..4733625 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1002,3 +1002,80 @@ int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
 
     return vfio_container_do_ioctl(as, groupid, req, param);
 }
+
+/*
+ * Interfaces for IBM EEH (Enhanced Error Handling)
+ */
+static bool vfio_eeh_container_ok(VFIOContainer *container)
+{
+    /* A broken kernel implementation means EEH operations won't work
+     * correctly if there are multiple groups in a container */
+
+    if (!QLIST_EMPTY(&container->group_list)
+        && QLIST_NEXT(QLIST_FIRST(&container->group_list), container_next)) {
+        return false;
+    }
+
+    return true;
+}
+
+static int vfio_eeh_container_op(VFIOContainer *container, uint32_t op)
+{
+    struct vfio_eeh_pe_op pe_op = {
+        .argsz = sizeof(pe_op),
+        .op = op,
+    };
+    int ret;
+
+    if (!vfio_eeh_container_ok(container)) {
+        error_report("vfio/eeh: EEH_PE_OP 0x%x called on container"
+                     " with multiple groups", op);
+        return -EPERM;
+    }
+
+    ret = ioctl(container->fd, VFIO_EEH_PE_OP, &pe_op);
+    if (ret < 0) {
+        error_report("vfio/eeh: EEH_PE_OP 0x%x failed: %m", op);
+        return -errno;
+    }
+
+    return 0;
+}
+
+static VFIOContainer *vfio_eeh_as_container(AddressSpace *as)
+{
+    VFIOAddressSpace *space = vfio_get_address_space(as);
+    VFIOContainer *container = NULL;
+
+    if (QLIST_EMPTY(&space->containers)) {
+        /* No containers to act on */
+        goto out;
+    }
+
+    container = QLIST_FIRST(&space->containers);
+
+    if (QLIST_NEXT(container, next)) {
+        /* We don't yet have logic to synchronize EEH state across
+         * multiple containers */
+        container = NULL;
+        goto out;
+    }
+
+out:
+    vfio_put_address_space(space);
+    return container;
+}
+
+bool vfio_eeh_as_ok(AddressSpace *as)
+{
+    VFIOContainer *container = vfio_eeh_as_container(as);
+
+    return (container != NULL) && vfio_eeh_container_ok(container);
+}
+
+int vfio_eeh_as_op(AddressSpace *as, uint32_t op)
+{
+    VFIOContainer *container = vfio_eeh_as_container(as);
+
+    return vfio_eeh_container_op(container, op);
+}
diff --git a/include/hw/vfio/vfio.h b/include/hw/vfio/vfio.h
index 0b26cd8..fd3933b 100644
--- a/include/hw/vfio/vfio.h
+++ b/include/hw/vfio/vfio.h
@@ -5,5 +5,7 @@
 
 extern int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
                                 int req, void *param);
+bool vfio_eeh_as_ok(AddressSpace *as);
+int vfio_eeh_as_op(AddressSpace *as, uint32_t op);
 
 #endif
-- 
2.5.0