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Subject[PATCH 1/1] Drivers: hv: balloon: Enable dynamic memory protocol negotiation with Windows 10 hosts
Date
From: Alex Ng <alexng@microsoft.com>

This enables dynamic protocol support on Windows 10 Hyper-V hosts.
If the host does not support Windows 10 protocol, then it falls back to
previous versions.

The change allows guests on Windows 10 Hyper-V hosts to hot-add memory
even when dynamic memory is not enabled on the guest.

Signed-off-by: Alex Ng <alexng@microsoft.com>
---
drivers/hv/hv_balloon.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index cb5b7dc..15be14b 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -62,11 +62,13 @@
enum {
DYNMEM_PROTOCOL_VERSION_1 = DYNMEM_MAKE_VERSION(0, 3),
DYNMEM_PROTOCOL_VERSION_2 = DYNMEM_MAKE_VERSION(1, 0),
+ DYNMEM_PROTOCOL_VERSION_3 = DYNMEM_MAKE_VERSION(2, 0),

DYNMEM_PROTOCOL_VERSION_WIN7 = DYNMEM_PROTOCOL_VERSION_1,
DYNMEM_PROTOCOL_VERSION_WIN8 = DYNMEM_PROTOCOL_VERSION_2,
+ DYNMEM_PROTOCOL_VERSION_WIN10 = DYNMEM_PROTOCOL_VERSION_3,

- DYNMEM_PROTOCOL_VERSION_CURRENT = DYNMEM_PROTOCOL_VERSION_WIN8
+ DYNMEM_PROTOCOL_VERSION_CURRENT = DYNMEM_PROTOCOL_VERSION_WIN10
};


@@ -1294,13 +1296,25 @@ static void version_resp(struct hv_dynmem_device *dm,
if (dm->next_version == 0)
goto version_error;

- dm->next_version = 0;
memset(&version_req, 0, sizeof(struct dm_version_request));
version_req.hdr.type = DM_VERSION_REQUEST;
version_req.hdr.size = sizeof(struct dm_version_request);
version_req.hdr.trans_id = atomic_inc_return(&trans_id);
- version_req.version.version = DYNMEM_PROTOCOL_VERSION_WIN7;
- version_req.is_last_attempt = 1;
+ version_req.version.version = dm->next_version;
+
+ /*
+ * Set the next version to try in case current version fails.
+ * Win7 protocol ought to be the last one to try.
+ */
+ if (version_req.version.version == DYNMEM_PROTOCOL_VERSION_WIN8) {
+ dm->next_version = DYNMEM_PROTOCOL_VERSION_WIN7;
+ version_req.is_last_attempt = 0;
+ } else if (version_req.version.version ==
+ DYNMEM_PROTOCOL_VERSION_WIN7) {
+
+ dm->next_version = 0;
+ version_req.is_last_attempt = 1;
+ }

ret = vmbus_sendpacket(dm->dev->channel, &version_req,
sizeof(struct dm_version_request),
@@ -1440,7 +1454,7 @@ static int balloon_probe(struct hv_device *dev,

dm_device.dev = dev;
dm_device.state = DM_INITIALIZING;
- dm_device.next_version = DYNMEM_PROTOCOL_VERSION_WIN7;
+ dm_device.next_version = DYNMEM_PROTOCOL_VERSION_WIN8;
init_completion(&dm_device.host_event);
init_completion(&dm_device.config_event);
INIT_LIST_HEAD(&dm_device.ha_region_list);
@@ -1472,7 +1486,7 @@ static int balloon_probe(struct hv_device *dev,
version_req.hdr.type = DM_VERSION_REQUEST;
version_req.hdr.size = sizeof(struct dm_version_request);
version_req.hdr.trans_id = atomic_inc_return(&trans_id);
- version_req.version.version = DYNMEM_PROTOCOL_VERSION_WIN8;
+ version_req.version.version = DYNMEM_PROTOCOL_VERSION_WIN10;
version_req.is_last_attempt = 0;

ret = vmbus_sendpacket(dev->channel, &version_req,
--
1.8.5.2


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