RE: [PATCH 1/1] Drivers: hv: vmbus: fix init_vp_index() for reloading hv_netvsc

[KY Srinivasan]

> -----Original Message-----
> From: James Bottomley [mailto:James.Bottomley@xxxxxxxxxxxxxxxxxxxxx]
> Sent: Thursday, August 13, 2015 4:09 PM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; ohering@xxxxxxxx;
> jbottomley@xxxxxxxxxxxxx; hch@xxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx;
> apw@xxxxxxxxxxxxx; vkuznets@xxxxxxxxxx; jasowang@xxxxxxxxxx;
> Dexuan Cui <decui@xxxxxxxxxxxxx>
> Subject: Re: [PATCH 1/1] Drivers: hv: vmbus: fix init_vp_index() for reloading
> hv_netvsc
> 
> On Thu, 2015-08-13 at 17:07 -0700, K. Y. Srinivasan wrote:
> > From: Dexuan Cui <decui@xxxxxxxxxxxxx>
> >
> > This fixes the recent commit 3b71107d73b16074afa7658f3f0fcf837aabfe24:
> 
> Which tree is this in?  upstream linus is giving me bad object on that
> id.

Greg's char-misc tree.
> 
> 
> > Drivers: hv: vmbus: Further improve CPU affiliation logic
> >
> > Without the fix, reloading hv_netvsc hangs the guest.
> 
> The reason for looking for the commit id was to see if cc to stable was
> necessary, is it?
The offending patch was committed on August 5th and cc to stable was not necessary.

K. Y
> 
> James
> 
> > Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> > Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> > ---
> >  drivers/hv/channel_mgmt.c |   17 +++++++++++++++++
> >  1 files changed, 17 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> > index 3ab4753..8a4105c 100644
> > --- a/drivers/hv/channel_mgmt.c
> > +++ b/drivers/hv/channel_mgmt.c
> > @@ -204,6 +204,8 @@ void hv_process_channel_removal(struct
> vmbus_channel *channel, u32 relid)
> >  		spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
> >  		list_del(&channel->listentry);
> >  		spin_unlock_irqrestore(&vmbus_connection.channel_lock,
> flags);
> > +
> > +		primary_channel = channel;
> >  	} else {
> >  		primary_channel = channel->primary_channel;
> >  		spin_lock_irqsave(&primary_channel->lock, flags);
> > @@ -211,6 +213,14 @@ void hv_process_channel_removal(struct
> vmbus_channel *channel, u32 relid)
> >  		primary_channel->num_sc--;
> >  		spin_unlock_irqrestore(&primary_channel->lock, flags);
> >  	}
> > +
> > +	/*
> > +	 * We need to free the bit for init_vp_index() to work in the case
> > +	 * of sub-channel, when we reload drivers like hv_netvsc.
> > +	 */
> > +	cpumask_clear_cpu(channel->target_cpu,
> > +			  &primary_channel->alloced_cpus_in_node);
> > +
> >  	free_channel(channel);
> >  }
> >
> > @@ -457,6 +467,13 @@ static void init_vp_index(struct vmbus_channel
> *channel, const uuid_le *type_gui
> >  			continue;
> >  		}
> >
> > +		/*
> > +		 * NOTE: in the case of sub-channel, we clear the sub-channel
> > +		 * related bit(s) in primary->alloced_cpus_in_node in
> > +		 * hv_process_channel_removal(), so when we reload
> drivers
> > +		 * like hv_netvsc in SMP guest, here we're able to re-allocate
> > +		 * bit from primary->alloced_cpus_in_node.
> > +		 */
> >  		if (!cpumask_test_cpu(cur_cpu,
> >  				&primary->alloced_cpus_in_node)) {
> >  			cpumask_set_cpu(cur_cpu,
> 
>