Re: [BUG] Xen vm kernel crash in get_free_entries.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Dec 09, 2013 at 01:57:37PM +0100, Sander Eikelenboom wrote:
> 
> Friday, November 29, 2013, 12:54:16 PM, you wrote:
> 
> > On Thu, 28 Nov 2013, Konrad Rzeszutek Wilk wrote:
> >> On Thu, Nov 28, 2013 at 02:56:53PM +0000, Stefano Stabellini wrote:
> >> > On Tue, 26 Nov 2013, Konrad Rzeszutek Wilk wrote:
> >> > > On Wed, Nov 13, 2013 at 09:40:58AM +0000, Ian Campbell wrote:
> >> > > > On Tue, 2013-11-12 at 10:56 -0500, Konrad Rzeszutek Wilk wrote:
> >> > > > > On Thu, Nov 07, 2013 at 01:47:03PM +0000, Ian Campbell wrote:
> >> > > > > > On Thu, 2013-11-07 at 09:20 +0400, Astarta wrote:
> >> > > > > > > Hello,
> >> > > > > > > 
> >> > > > > > > Let me bring some new life to this discussion.
> >> > > > > > > 
> >> > > > > > > I've investigated a bit and found another way to make  kernels starting 
> >> > > > > > > from 3.8.x to boot on the VMs with platform device_id 0002.
> >> > > > > > > Reverting of xen-grant-table-correctly-initialize-grant-table-version-1 
> >> > > > > > > patch is not necessary.
> >> > > > > > > 
> >> > > > > > > We can simply modify struct pci_device_id platform_pci_tbl[] (in 
> >> > > > > > > drivers/xen/platform-pci.c) to respect 0002 and 0000 device ids.
> >> > > > > > > That makes the kernel (3.8.x and 3.11.6) to boot correctly, disks and 
> >> > > > > > > network are also recognized.
> >> > > > > > 
> >> > > > > > I think this is just working around the problem, by avoiding the
> >> > > > > > situation where the error occurs. You could just as well switch to
> >> > > > > > platform device id < 2.
> >> > > > > 
> >> > > > > I am bit late to this discussion - but shouldn't there be something
> >> > > > > in the kernel to deal with this?
> >> > > > 
> >> > > > Well, ideally the kernel wouldn't crash ;-)
> >> > > 
> >> > > This patch should solve that (untested, but at least compile tested):
> >> > > Please test it.
> >> > > 
> >> > > >From f7d3581aa19a35ea3ff10b965b2b08843e923635 Mon Sep 17 00:00:00 2001
> >> > > From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> >> > > Date: Tue, 26 Nov 2013 15:05:40 -0500
> >> > > Subject: [PATCH] xen/pvhvm: If xen_platform_pci=0 is set don't blow up.
> >> > > 
> >> > > *TODO*
> >> > > 
> >> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> >> > > ---
> >> > >  drivers/block/xen-blkfront.c               |  2 +-
> >> > >  drivers/input/misc/xen-kbdfront.c          |  4 ++++
> >> > >  drivers/net/xen-netfront.c                 |  2 +-
> >> > >  drivers/xen/xenbus/xenbus_probe_frontend.c |  2 +-
> >> > >  include/xen/platform_pci.h                 | 13 +++++++++++++
> >> > >  5 files changed, 20 insertions(+), 3 deletions(-)
> >> > > 
> >> > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> >> > > index 432db1b..bcbaf0b 100644
> >> > > --- a/drivers/block/xen-blkfront.c
> >> > > +++ b/drivers/block/xen-blkfront.c
> >> > > @@ -2074,7 +2074,7 @@ static int __init xlblk_init(void)
> >> > >          if (!xen_domain())
> >> > >           return -ENODEV;
> >> > >  
> >> > > -        if (xen_hvm_domain() && !xen_platform_pci_unplug)
> >> > > +        if (xen_err_out())
> >> > >           return -ENODEV;
> >> > >  
> >> > >          if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
> >> > > diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
> >> > > index e21c181..9d250cf 100644
> >> > > --- a/drivers/input/misc/xen-kbdfront.c
> >> > > +++ b/drivers/input/misc/xen-kbdfront.c
> >> > > @@ -29,6 +29,7 @@
> >> > >  #include <xen/interface/io/fbif.h>
> >> > >  #include <xen/interface/io/kbdif.h>
> >> > >  #include <xen/xenbus.h>
> >> > > +#include <xen/platform_pci.h>
> >> > >  
> >> > >  struct xenkbd_info {
> >> > >          struct input_dev *kbd;
> >> > > @@ -380,6 +381,9 @@ static int __init xenkbd_init(void)
> >> > >          if (xen_initial_domain())
> >> > >           return -ENODEV;
> >> > >  
> >> > > +        if (xen_err_out())
> >> > > +         return -ENODEV;
> >> > 
> >> > Why do we error out here? There is nothing to unplug in this case.
> >> 
> >> B/c otherwise the driver blows up when it acts on the XenBus and tries
> >> to setup a grant. But the grant is initialized by the xen-platform-pci
> >> which is not run.
> 
> > I see. Adding this check must be the real purpose of the patch then?
> > In that case don't we need another check like this one in:
> 
> > drivers/char/tpm/xen-tpmfront.c:xen_tpmfront_init
> > drivers/pci/xen-pcifront.c:pcifront_init
> 
> > and for consistency (it doesn't use grants right now)
> 
> > drivers/video/xen-fbfront.c:xenfb_init
> 
> > ?
> 
> 
> Hi Konrad / Stefano,
> 
> Is there any follow up on this ?

I need to respin it. Um, will do that later on today. Thanks for
poking me!
> 
> --
> Sander
>