linux-kernel - Re: [PANIC, hyperv] BUG: unable to handle kernel paging request at ffff880077800004 (hv_ringbuffer

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Date:	Wed, 27 Aug 2014 23:57:39 +0100
From:	Sitsofe Wheeler <sitsofe@...il.com>
To:	KY Srinivasan <kys@...rosoft.com>
Cc:	Dexuan Cui <decui@...rosoft.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PANIC, hyperv] BUG: unable to handle kernel paging request at
 ffff880077800004 (hv_ringbuffer_write)

On Wed, Aug 27, 2014 at 06:45:55PM +0000, KY Srinivasan wrote:
> 
> > -----Original Message-----
> > From: Sitsofe Wheeler [mailto:sitsofe@...il.com]
> > Sent: Wednesday, August 27, 2014 9:19 AM
> > 
> > > BTW, with the patch below, hyperv_fb can work now, BUT,
> > > *occasionally*,
> > > storvsc_probe() -> ... -> vmbus_open() -> can fail due to
> > > HV_STATUS_INVALID_ALIGNMENT...
> > 
> > I applied your new patch on top of KY's pieces (it applied cleanly)
> > and while it doesn't blow up, one warning is printed out and the UP
> > boot seemed to stall after input: TPPS/2 message (but pressing
> > ctrl-alt-delete allows the system to reboot cleanly).
> 
> First let me thank you guys for looking into this issue. Looking at
> your dmesg, it looked like storvsc probe failed as Dexuan had seen.
> Since the failure appears to be alignment related, perhaps we could
> test with allocating a page all the time (and getting rid of the
> kmalloc). Sitsofe, here is a patch based on Dexuan's patch. If this
> works, I will probably minimize failure cases by pre-allocating
> per-cpu pages for this.:

After some modifications to apply on top of your previous patches
applying this latest patch has cured the issues surrounding hyperv_fb
issues on boot. The only issue seen on boot now is similar to
https://lkml.org/lkml/2014/8/19/227 ...

How come previous alignment efforts weren't working out?

-- 
Sitsofe | http://sucs.org/~sits/
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