Drivers: hv: balloon: Permit Linux to specify hot-add alignment requirements

Some Windows hosts permit the guest to specify memory hot-add alignment
requirements (if any). Linux currently requires a 128MB alignment on memory
segments that can be hot-added. Specify this alignment requirement to the
host.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index d5225261ee54..2250bf532bb0 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -117,7 +117,14 @@ union dm_caps {
         struct {
                 __u64 balloon:1;
                 __u64 hot_add:1;
-                __u64 reservedz:62;
+                /*
+                 * To support guests that may have alignment
+                 * limitations on hot-add, the guest can specify
+                 * its alignment requirements; a value of n
+                 * represents an alignment of 2^n in mega bytes.
+                 */
+                __u64 hot_add_alignment:4;
+                __u64 reservedz:58;
         } cap_bits;
         __u64 caps;
 } __packed;
@@ -774,7 +781,7 @@ static unsigned long process_hot_add(unsigned long pg_start,
          * If the host has specified a hot-add range; deal with it first.
          */
 
-        if ((rg_size != 0) && (!dm_device.host_specified_ha_region)) {
+        if (rg_size != 0) {
                 ha_region = kzalloc(sizeof(struct hv_hotadd_state), GFP_KERNEL);
                 if (!ha_region)
                         return 0;
@@ -1367,6 +1374,12 @@ static int balloon_probe(struct hv_device *dev,
         cap_msg.caps.cap_bits.hot_add = 1;
 
         /*
+         * Specify our alignment requirements as it relates
+         * memory hot-add. Specify 128MB alignment.
+         */
+        cap_msg.caps.cap_bits.hot_add_alignment = 7;
+
+        /*
          * Currently the host does not use these
          * values and we set them to what is done in the
          * Windows driver.