spapr: Ensure all LMBs are represented in ibm,dynamic-memory
Memory hotplug can fail for some combinations of RAM and maxmem when
DDW is enabled in the presence of devices like nec-usb-xhci. DDW depends
on maximum addressable memory returned by guest and this value is currently
being calculated wrongly by the guest kernel routine memory_hotplug_max().
While there is an attempt to fix the guest kernel, this patch works
around the problem within QEMU itself.
memory_hotplug_max() routine in the guest kernel arrives at max
addressable memory by multiplying lmb-size with the lmb-count obtained
from ibm,dynamic-memory property. There are two assumptions here:
- All LMBs are part of ibm,dynamic memory: This is not true for PowerKVM
where only hot-pluggable LMBs are present in this property.
- The memory area comprising of RAM and hotplug region is contiguous: This
needn't be true always for PowerKVM as there can be gap between
boot time RAM and hotplug region.
To work around this guest kernel bug, ensure that ibm,dynamic-memory
has information about all the LMBs (RMA, boot-time LMBs, future
hotpluggable LMBs, and dummy LMBs to cover the gap between RAM and
hotpluggable region).
RMA is represented separately by memory@0 node. Hence mark RMA LMBs
and also the LMBs for the gap b/n RAM and hotpluggable region as
reserved and as having no valid DRC so that these LMBs are not considered
by the guest.
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 971df3d..3ac85c0 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -620,9 +620,11 @@
#define SPAPR_DR_LMB_LIST_ENTRY_SIZE 6
/*
- * This flag value defines the LMB as assigned in ibm,dynamic-memory
- * property under ibm,dynamic-reconfiguration-memory node.
+ * Defines for flag value in ibm,dynamic-memory property under
+ * ibm,dynamic-reconfiguration-memory node.
*/
#define SPAPR_LMB_FLAGS_ASSIGNED 0x00000008
+#define SPAPR_LMB_FLAGS_DRC_INVALID 0x00000020
+#define SPAPR_LMB_FLAGS_RESERVED 0x00000080
#endif /* !defined (__HW_SPAPR_H__) */
