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authorAndrea Parri <parri.andrea@gmail.com>2019-10-15 13:46:46 +0200
committerSasha Levin <sashal@kernel.org>2019-11-21 20:10:44 -0500
commit931cccc967730d43bb6325506baf51c8f83a9a58 (patch)
tree3ac845e171b98d698f1ff123385b314bb36a4b9d /drivers/hv/connection.c
parent2d4f49b3e1e3a24ce16dfeeb2235688c8aba57ef (diff)
Drivers: hv: vmbus: Add module parameter to cap the VMBus version
Currently, Linux guests negotiate the VMBus version with Hyper-V and use the highest available VMBus version they can connect to. This has some drawbacks: by using the highest available version, certain code paths are never executed and can not be tested when the guest runs on the newest host. Add the module parameter "max_version", to upper-bound the VMBus versions guests can negotiate. Suggested-by: Dexuan Cui <decui@microsoft.com> Signed-off-by: Andrea Parri <parri.andrea@gmail.com> Reviewed-by: Wei Liu <wei.liu@kernel.org> Reviewed-by: Michael Kelley <mikelley@microsoft.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/hv/connection.c')
-rw-r--r--drivers/hv/connection.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index cadfb34b38d8..0475be4356dd 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -14,6 +14,7 @@
#include <linux/wait.h>
#include <linux/delay.h>
#include <linux/mm.h>
+#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/hyperv.h>
@@ -55,6 +56,16 @@ static __u32 vmbus_versions[] = {
VERSION_WS2008
};
+/*
+ * Maximal VMBus protocol version guests can negotiate. Useful to cap the
+ * VMBus version for testing and debugging purpose.
+ */
+static uint max_version = VERSION_WIN10_V5_2;
+
+module_param(max_version, uint, S_IRUGO);
+MODULE_PARM_DESC(max_version,
+ "Maximal VMBus protocol version which can be negotiated");
+
int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
{
int ret = 0;
@@ -240,6 +251,8 @@ int vmbus_connect(void)
goto cleanup;
version = vmbus_versions[i];
+ if (version > max_version)
+ continue;
ret = vmbus_negotiate_version(msginfo, version);
if (ret == -ETIMEDOUT)