Re: [Qemu-devel] [Qemu-ppc] [PATCH v2] spapr: fix memory hotplug error path

[Daniel Henrique Barboza]

On 07/03/2017 11:54 AM, Greg Kurz wrote:
QEMU shouldn't abort if spapr_add_lmbs()->spapr_drc_attach() fails.
Let's propagate the error instead, like it is done everywhere else
where spapr_drc_attach() is called.

Signed-off-by: Greg Kurz <gr...@kaod.org>
---
Changes in v2: - added rollback code
---
  hw/ppc/spapr.c |   26 ++++++++++++++++++++++----
  1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 70b3fd374e2b..ba8f57a5a054 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2601,6 +2601,7 @@ static void spapr_add_lmbs(DeviceState *dev, uint64_t 
addr_start, uint64_t size,
      int i, fdt_offset, fdt_size;
      void *fdt;
      uint64_t addr = addr_start;
+    Error *local_err = NULL;

      for (i = 0; i < nr_lmbs; i++) {
          drc = spapr_drc_by_id(TYPE_SPAPR_DRC_LMB,
@@ -2611,7 +2612,18 @@ static void spapr_add_lmbs(DeviceState *dev, uint64_t 
addr_start, uint64_t size,
          fdt_offset = spapr_populate_memory_node(fdt, node, addr,
                                                  SPAPR_MEMORY_BLOCK_SIZE);

-        spapr_drc_attach(drc, dev, fdt, fdt_offset, errp);
+        spapr_drc_attach(drc, dev, fdt, fdt_offset, &local_err);
+        if (local_err) {
+            while (addr > addr_start) {
+                addr -= SPAPR_MEMORY_BLOCK_SIZE;
+                drc = spapr_drc_by_id(TYPE_SPAPR_DRC_LMB,
+                                      addr / SPAPR_MEMORY_BLOCK_SIZE);
+                spapr_drc_detach(drc, dev, NULL);

Question: why pass NULL instead of '&local_err' in detach() ? Can we 
ignore any
any error that happens in detach() because you're propagating the 
local_err set
in spapr_drc_attach() already?

ps: I am aware that ATM detach() does not propagate anything to the errp 
being
passed. I don't think it's wise to write new code based on this 
assumption though.


Thanks,


Daniel

+            }
+            g_free(fdt);
+            error_propagate(errp, local_err);
+            return;
+        }
          addr += SPAPR_MEMORY_BLOCK_SIZE;
      }
      /* send hotplug notification to the
@@ -2651,14 +2663,20 @@ static void spapr_memory_plug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
      addr = object_property_get_uint(OBJECT(dimm),
                                      PC_DIMM_ADDR_PROP, &local_err);
      if (local_err) {
-        pc_dimm_memory_unplug(dev, &ms->hotplug_memory, mr);
-        goto out;
+        goto out_unplug;
      }

      spapr_add_lmbs(dev, addr, size, node,
                     spapr_ovec_test(ms->ov5_cas, OV5_HP_EVT),
-                   &error_abort);
+                   &local_err);
+    if (local_err) {
+        goto out_unplug;
+    }
+
+    return;

+out_unplug:
+    pc_dimm_memory_unplug(dev, &ms->hotplug_memory, mr);
  out:
      error_propagate(errp, local_err);
  }