linux-kernel - RE: [PATCH] Drivers: hv: kvp/vss: Avoid accessing a ringbuffer not initialized yet

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Message-ID:
 <SN6PR02MB4157D9B44F3B94E17993BB6DD4562@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Fri, 1 Nov 2024 01:38:33 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Dexuan Cui <decui@...rosoft.com>, KY Srinivasan <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Vitaly
 Kuznetsov <vkuznets@...hat.com>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, "open list:Hyper-V/Azure CORE AND DRIVERS"
	<linux-hyperv@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
CC: "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] Drivers: hv: kvp/vss: Avoid accessing a ringbuffer not
 initialized yet

From: Dexuan Cui <decui@...rosoft.com> Sent: Thursday, October 31, 2024 5:17 PM
> 
> > From: Michael Kelley <mhklinux@...look.com>
> > Sent: Wednesday, October 30, 2024 5:12 PM
> > [...]
> > What do you think about this (compile tested only), which splits the
> > "init" function into two parts for devices that have char devs? I'm
> > trying to avoid adding yet another synchronization point by just
> > doing the init operations in the right order -- i.e., don't create the
> > user space /dev entry until the VMBus channel is ready.
> >
> > Michael
> 
> Thanks, I think this works! This is a better fix.
> 
> > +	if (srv->util_init_transport) {
> > +		ret = srv->util_init_transport();
> > +		if (ret) {
> > +			ret = -ENODEV;
> IMO we don't need the line above, since the 'ret' from
> srv->util_init_transport()  is already a standard error code.

I was just now looking at call_driver_probe(), and it behaves
slightly differently for ENODEV and ENXIO vs. other error
codes. ENODEV and ENXIO don't output a message to the
console unless debugging is enabled, while other error codes
always output a message to the console. Forcing the error to
ENODEV has been there since the util_probe() code came out
of staging in year 2011. But I don't really have a preference
either way.

> 
> BTW, I noticed that the line "ret = -ENODEV;"
>         if (srv->util_init) {
>                 ret = srv->util_init(srv);
>                 if (ret) {
>                         ret = -ENODEV;
>                         goto error1;
>                 }
>         }
> I think we don't really need that line, either.
> The existing 4 .util_init callbacks also already return a
> standard error code. We can make a separate patch to clean
> that up.

Same here.

Michael