powerpc/numa: Fix multiple bugs in memory_hotplug_max()

memory_hotplug_max() uses hot_add_drconf_memory_max() to get maxmimum
addressable memory by referring to ibm,dyanamic-memory property. There
are three problems with the current approach:

1 hot_add_drconf_memory_max() assumes that ibm,dynamic-memory includes
  all the LMBs of the guest, but that is not true for PowerKVM which
  populates only DR LMBs (LMBs that can be hotplugged/removed) in that
  property.
2 hot_add_drconf_memory_max() multiplies lmb-size with lmb-count to arrive
  at the max possible address. Since ibm,dynamic-memory doesn't include
  RMA LMBs, the address thus obtained will be less than the actual max
  address. For example, if max possible memory size is 32G, with lmb-size
  of 256MB there can be 127 LMBs in ibm,dynamic-memory (1 LMB for RMA
  which won't be present here).  hot_add_drconf_memory_max() would then
  return the max addressable memory as 127 * 256MB = 31.75GB, the max
  address should have been 32G which is what ibm,lrdr-capacity shows.
3 In PowerKVM, there can be a gap between the end of boot time RAM and
  beginning of hotplug RAM area. So just multiplying lmb-count with
  lmb-size will not provide the correct max possible address for PowerKVM.

This patch fixes 1 by using ibm,lrdr-capacity property to return the max
addressable memory whenever the property is present. Then it fixes 2 & 3
by fetching the address of the last LMB in ibm,dynamic-memory property.

Fixes: cd34206e949b ("powerpc: Add memory_hotplug_max()")
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 4a87ccb8970fd15caa325bd907a085e67341484a..f8b1da77671270b78b4fbc0e4484adae8bf924ce 100644 (file)
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -1164,17 +1164,33 @@ int hot_add_scn_to_nid(unsigned long scn_addr)
 static u64 hot_add_drconf_memory_max(void)
 {
        struct device_node *memory = NULL;
+       struct device_node *dn = NULL;
        unsigned int drconf_cell_cnt = 0;
        u64 lmb_size = 0;
        const __be32 *dm = NULL;
+       const __be64 *lrdr = NULL;
+       struct of_drconf_cell drmem;
+
+       dn = of_find_node_by_path("/rtas");
+       if (dn) {
+               lrdr = of_get_property(dn, "ibm,lrdr-capacity", NULL);
+               of_node_put(dn);
+               if (lrdr)
+                       return be64_to_cpup(lrdr);
+       }
 
        memory = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");
        if (memory) {
                drconf_cell_cnt = of_get_drconf_memory(memory, &dm);
                lmb_size = of_get_lmb_size(memory);
+
+               /* Advance to the last cell, each cell has 6 32 bit integers */
+               dm += (drconf_cell_cnt - 1) * 6;
+               read_drconf_cell(&drmem, &dm);
                of_node_put(memory);
+               return drmem.base_addr + lmb_size;
        }
-       return lmb_size * drconf_cell_cnt;
+       return 0;
 }
 
 /*