[PATCH v3 2/7] spapr_pci.c: simplify spapr_pci_unplug_request() function handling

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

When hotunplugging a PCI function we'll branch out the logic in two cases,
function zero and non-zero. If non-zero, we'll call spapr_drc_detach() and
nothing else. If it's function zero, we'll loop it once between all the
functions in the slot to call spapr_drc_detach() on them, and afterwards
we'll do another backwards loop where we'll signal the event to the guest.

We can simplify this logic. We can ignore all the DRC handling for non-zero
functions, since we'll end up doing that regardless when unplugging function
zero. And for function zero, everything can be done in a single loop, since
tt doesn't matter if we end up marking the function DRCs as unplug pending in
backwards order or not, as long as we call spapr_drc_detach() before issuing
the hotunplug event to the guest.

This will also avoid a possible scenario where the user starts to hotunplug
the slot, starting with a non-zero function, and then delays/forgets to
hotunplug function zero afterwards. This would keep the function DRC marked
as unplug requested indefinitely.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 hw/ppc/spapr_pci.c | 44 ++++++++++++++++----------------------------
 1 file changed, 16 insertions(+), 28 deletions(-)

diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index f1c7479816..1791d98a49 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1709,38 +1709,26 @@ static void spapr_pci_unplug_request(HotplugHandler *plug_handler,
             return;
         }
 
-        /* ensure any other present functions are pending unplug */
-        if (PCI_FUNC(pdev->devfn) == 0) {
-            for (i = 1; i < 8; i++) {
-                func_drc = drc_from_devfn(phb, chassis, PCI_DEVFN(slotnr, i));
-                func_drck = SPAPR_DR_CONNECTOR_GET_CLASS(func_drc);
-                state = func_drck->dr_entity_sense(func_drc);
-                if (state == SPAPR_DR_ENTITY_SENSE_PRESENT
-                    && !spapr_drc_unplug_requested(func_drc)) {
-                    /*
-                     * Attempting to remove function 0 of a multifunction
-                     * device will will cascade into removing all child
-                     * functions, even if their unplug weren't requested
-                     * beforehand.
-                     */
-                    spapr_drc_detach(func_drc);
-                }
-            }
+        /*
+         * The hotunplug itself will occur when unplugging function 0,
+         * regardless of marking any other functions DRCs as pending
+         * unplug beforehand (since 02a1536eee33).
+         */
+        if (PCI_FUNC(pdev->devfn) != 0) {
+            return;
         }
 
-        spapr_drc_detach(drc);
+        for (i = 7; i >= 0; i--) {
+            func_drc = drc_from_devfn(phb, chassis, PCI_DEVFN(slotnr, i));
+            func_drck = SPAPR_DR_CONNECTOR_GET_CLASS(func_drc);
+            state = func_drck->dr_entity_sense(func_drc);
 
-        /* if this isn't func 0, defer unplug event. otherwise signal removal
-         * for all present functions
-         */
-        if (PCI_FUNC(pdev->devfn) == 0) {
-            for (i = 7; i >= 0; i--) {
-                func_drc = drc_from_devfn(phb, chassis, PCI_DEVFN(slotnr, i));
-                func_drck = SPAPR_DR_CONNECTOR_GET_CLASS(func_drc);
-                state = func_drck->dr_entity_sense(func_drc);
-                if (state == SPAPR_DR_ENTITY_SENSE_PRESENT) {
-                    spapr_hotplug_req_remove_by_index(func_drc);
+            if (state == SPAPR_DR_ENTITY_SENSE_PRESENT) {
+                /* Mark the DRC as requested unplug if needed. */
+                if (!spapr_drc_unplug_requested(func_drc)) {
+                    spapr_drc_detach(func_drc);
                 }
+                spapr_hotplug_req_remove_by_index(func_drc);
             }
         }
     }
-- 
2.29.2