Re: [PATCH v2 2/3] hv: vmbus_post_msg: retry the hypercall on some transient errors

[Jason Wang <jasowang@redhat.com>]

On Mon, Feb 2, 2015 at 12:36 PM, Dexuan Cui <decui@microsoft.com> wrote:
> I got HV_STATUS_INVALID_CONNECTION_ID on Hyper-V 2008 R2 when keeping 
> running
> "rmmod hv_netvsc; modprobe hv_netvsc; rmmod hv_utils; modprobe 
> hv_utils"
> in a Linux guest. Looks the host has some kind of throttling 
> mechanism if
> some kinds of hypercalls are sent too frequently.

Better to clarify this kind of throttling. Looks like it only affects 
HVCALL_POST_MESSAGE. Other looks good.

Reviewed-by: Jason Wang <jasowang@redhat.com>
> 
> Without the patch, the driver can occasionally fail to load.
> 
> Also let's retry HV_STATUS_INSUFFICIENT_MEMORY, though we didn't get 
> it
> before.
> 
> Removed 'case -ENOMEM', since the hypervisor doesn't return this.
> 
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> ---
> 
> v2:
>   updated the subject and changelog
>   on HV_STATUS_INVALID_CONNECTION_ID: ret =  -EAGAIN;
>   added HV_STATUS_INSUFFICIENT_MEMORY
>   removed unreachable -ENOMEM
>   changed the delay from 100ms to 1000ms
>   
>  arch/x86/include/uapi/asm/hyperv.h |  2 ++
>  drivers/hv/connection.c            | 11 +++++++++--
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/uapi/asm/hyperv.h 
> b/arch/x86/include/uapi/asm/hyperv.h
> index 90c458e..ce6068d 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -225,6 +225,8 @@
>  #define HV_STATUS_INVALID_HYPERCALL_CODE	2
>  #define HV_STATUS_INVALID_HYPERCALL_INPUT	3
>  #define HV_STATUS_INVALID_ALIGNMENT		4
> +#define HV_STATUS_INSUFFICIENT_MEMORY		11
> +#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..af2388f 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -440,9 +440,16 @@ 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.
> +			 */
> +			ret = -EAGAIN;
> +			break;
> +		case HV_STATUS_INSUFFICIENT_MEMORY:
>  		case HV_STATUS_INSUFFICIENT_BUFFERS:
>  			ret = -ENOMEM;
> -		case -ENOMEM:
>  			break;
>  		case HV_STATUS_SUCCESS:
>  			return ret;
> @@ -452,7 +459,7 @@ int vmbus_post_msg(void *buffer, size_t buflen)
>  		}
>  
>  		retries++;
> -		msleep(100);
> +		msleep(1000);
>  	}
>  	return ret;
>  }
> -- 
> 1.9.1
>