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Drivers: hv: vmbus: Add module parameter to cap the VMBus version

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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>
This commit is contained in:
Andrea Parri 2019-10-15 13:46:46 +02:00 committed by Sasha Levin
parent 2d4f49b3e1
commit 931cccc967
1 changed files with 13 additions and 0 deletions
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13
drivers/hv/connection.c
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@ -14,6 +14,7 @@
#include <linux/wait.h> #include <linux/wait.h>
#include <linux/delay.h> #include <linux/delay.h>
#include <linux/mm.h> #include <linux/mm.h>
#include <linux/module.h>
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/vmalloc.h> #include <linux/vmalloc.h>
#include <linux/hyperv.h> #include <linux/hyperv.h>
@ -55,6 +56,16 @@ static __u32 vmbus_versions[] = {
VERSION_WS2008 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 vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
{ {
int ret = 0; int ret = 0;
@ -240,6 +251,8 @@ int vmbus_connect(void)
goto cleanup; goto cleanup;
version = vmbus_versions[i]; version = vmbus_versions[i];
if (version > max_version)
continue;
ret = vmbus_negotiate_version(msginfo, version); ret = vmbus_negotiate_version(msginfo, version);
if (ret == -ETIMEDOUT) if (ret == -ETIMEDOUT)