linux-kernel - RE: [PATCH 2/3] hv: vmbus_post_msg: retry the hypercall on HV_STATUS_INVALID_CONNECTION

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Date:	Fri, 30 Jan 2015 05:34:27 +0000
From:	Dexuan Cui <decui@...rosoft.com>
To:	Jason Wang <jasowang@...hat.com>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>,
	KY Srinivasan <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>
Subject: RE: [PATCH 2/3] hv: vmbus_post_msg: retry the hypercall on
 HV_STATUS_INVALID_CONNECTION_ID

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@...hat.com]
> Sent: Friday, January 30, 2015 10:47 AM
> To: Dexuan Cui
> Cc: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org; driverdev-
> devel@...uxdriverproject.org; olaf@...fle.de; apw@...onical.com; KY
> Srinivasan; Haiyang Zhang
> Subject: Re: [PATCH 2/3] hv: vmbus_post_msg: retry the hypercall on
> HV_STATUS_INVALID_CONNECTION_ID
> 
> 
> 
> On Thu, Jan 29, 2015 at 7:02 PM, Dexuan Cui <decui@...rosoft.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" <kys@...rosoft.com>
> > Signed-off-by: Dexuan Cui <decui@...rosoft.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.
The description about the 'low host resource condition' might be not accurate.
I'll remove this part.

> > +			msleep(1000);
> > +			break;
> >  		case HV_STATUS_INSUFFICIENT_BUFFERS:
> >  			ret = -ENOMEM;
> 
> I thought host should return this error value when lacking resources?
This should be correct.

> >
> >  		case -ENOMEM:
> > --

Thanks,
-- Dexuan