[PATCH v3 1/7] spapr_drc.c: do not call spapr_drc_detach() in drc_isolate_logical()

[Daniel Henrique Barboza <danielhb413@gmail.com>]

drc_isolate_logical() is used to move the DRC from the "Configured" to the
"Available" state, erroring out if the DRC is in the unexpected "Unisolate"
state and doing nothing (with RTAS_OUT_SUCCESS) if the DRC is already in
"Available" or in "Unusable" state.

When moving from "Configured" to "Available", the DRC is moved to the
LOGICAL_AVAILABLE state, a drc->unplug_requested check is done and, if true,
spapr_drc_detach() is called.

What spapr_drc_detach() does then is:

- set drc->unplug_requested to true. In fact, this is the only place where
unplug_request is set to true;
- does nothing else if drc->state != drck->empty_state. If the DRC state
is equal to drck->empty_state, spapr_drc_release() is called. For logical
DRCs, drck->empty_state = LOGICAL_UNUSABLE.

In short, calling spapr_drc_detach() in drc_isolate_logical() does nothing. It'll
set unplug_request to true again ('again' since it was already true - otherwise the
function wouldn't be called), and will return without calling spapr_drc_release()
because the DRC is not in LOGICAL_UNUSABLE, since drc_isolate_logical() just
moved it to LOGICAL_AVAILABLE. The only place where the logical DRC is released
is when called from drc_set_unusable(), when it is moved to the "Unusable" state.
As it should, according to PAPR.

Even though calling spapr_drc_detach() in drc_isolate_logical() is benign, removing
it will avoid further thought about the matter. So let's go ahead and do that.

As a note, this logic was introduced in commit bbf5c878ab76. Since then, the DRC
handling code was refactored and enhanced, and PAPR itself went through some
changes in the DRC area as well. It is expected that some assumptions we had back
then are now deprecated.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 hw/ppc/spapr_drc.c | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
index 8571d5bafe..84bd3c881f 100644
--- a/hw/ppc/spapr_drc.c
+++ b/hw/ppc/spapr_drc.c
@@ -132,19 +132,6 @@ static uint32_t drc_isolate_logical(SpaprDrc *drc)
 
     drc->state = SPAPR_DRC_STATE_LOGICAL_AVAILABLE;
 
-    /* if we're awaiting release, but still in an unconfigured state,
-     * it's likely the guest is still in the process of configuring
-     * the device and is transitioning the devices to an ISOLATED
-     * state as a part of that process. so we only complete the
-     * removal when this transition happens for a device in a
-     * configured state, as suggested by the state diagram from PAPR+
-     * 2.7, 13.4
-     */
-    if (drc->unplug_requested) {
-        uint32_t drc_index = spapr_drc_index(drc);
-        trace_spapr_drc_set_isolation_state_finalizing(drc_index);
-        spapr_drc_detach(drc);
-    }
     return RTAS_OUT_SUCCESS;
 }
 
-- 
2.29.2