On Thu, Jan 29, 2015 at 7:02 PM, Dexuan Cui <de...@microsoft.com> wrote:
I got the hypercall error code on Hyper-V 2008 R2 when keeping running
"rmmod hv_netvsc; modprobe hv_netvsc; rmmod hv_utils; modprobe hv_utils"
in a Linux guest.

Without the patch, the driver can occasionally fail to load.

CC: "K. Y. Srinivasan" <k...@microsoft.com>
Signed-off-by: Dexuan Cui <de...@microsoft.com>
---
 arch/x86/include/uapi/asm/hyperv.h | 1 +
 drivers/hv/connection.c            | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 90c458e..b9daffb 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -225,6 +225,7 @@
 #define HV_STATUS_INVALID_HYPERCALL_CODE       2
 #define HV_STATUS_INVALID_HYPERCALL_INPUT      3
 #define HV_STATUS_INVALID_ALIGNMENT            4
+#define HV_STATUS_INVALID_CONNECTION_ID                18
 #define HV_STATUS_INSUFFICIENT_BUFFERS         19
typedef struct _HV_REFERENCE_TSC_PAGE {
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index c4acd1c..8bd05f3 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -440,6 +440,15 @@ int vmbus_post_msg(void *buffer, size_t buflen)
                ret = hv_post_message(conn_id, 1, buffer, buflen);
switch (ret) {
+               case HV_STATUS_INVALID_CONNECTION_ID:
+                       /*
+                        * We could get this if we send messages too
+                        * frequently or the host is under low resource
+                        * conditions: let's wait 1 more second before
+                        * retrying the hypercall.
+                        */

The name HV_STATUS_INVALID_CONNECTION_ID is really confusing in this case. Since it does not show any meaning of lacking resources.
+                       msleep(1000);
+                       break;
                case HV_STATUS_INSUFFICIENT_BUFFERS:
                        ret = -ENOMEM;

I thought host should return this error value when lacking resources?

                case -ENOMEM:
--
1.9.1

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