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

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

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;
+
 	return xenbus_register_frontend(&xenkbd_driver);
 }
 
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index e59acb1..be2744b 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -2115,7 +2115,7 @@ static int __init netif_init(void)
 	if (!xen_domain())
 		return -ENODEV;
 
-	if (xen_hvm_domain() && !xen_platform_pci_unplug)
+	if (xen_err_out())
 		return -ENODEV;
 
 	pr_info("Initialising Xen virtual ethernet driver\n");
diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
index 129bf84..b1c0f2a 100644
--- a/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -496,7 +496,7 @@ subsys_initcall(xenbus_probe_frontend_init);
 #ifndef MODULE
 static int __init boot_wait_for_devices(void)
 {
-	if (xen_hvm_domain() && !xen_platform_pci_unplug)
+	if (xen_err_out())
 		return -ENODEV;
 
 	ready_to_wait_for_devices = 1;
diff --git a/include/xen/platform_pci.h b/include/xen/platform_pci.h
index 438c256..a5bbd0b 100644
--- a/include/xen/platform_pci.h
+++ b/include/xen/platform_pci.h
@@ -47,5 +47,18 @@ static inline int xen_must_unplug_disks(void) {
 }
 
 extern int xen_platform_pci_unplug;
+static  bool xen_err_out(void)
+{
 
+	if (!xen_domain())
+		return true;
+
+	if (xen_hvm_domain()) {
+		if (xen_platform_pci_unplug & (XEN_UNPLUG_UNNECESSARY | XEN_UNPLUG_NEVER))
+			return true;
+		if (xen_platform_pci_unplug == 0)
+			return true;
+	}
+	return false;
+}
 #endif /* _XEN_PLATFORM_PCI_H */
-- 
1.8.3.1

> 
> I don't think it would be appropriate for Linux to bind to the device
> with ID 2, since that has been assigned to a vendor
> http://xenbits.xen.org/docs/unstable/hypercall/x86_64/include,public,hvm,pvdrivers.h.html
> it should be up to them to define the ABI of that device and provide a
> Linux binding if they want.
> 
> Perhaps the unplug protocol
> http://xenbits.xen.org/docs/unstable/misc/xen-command-line.html needs
> expanding to blacklist products based on the presence absence of
> whichever platform device subids there are.
> 
> I'm a bit confused because I thought the requirement was that the base
> level platform device was always present and the secondary ones (like
> the Citrix PV device with ID 2) would only ever be additional. Maybe I'm
> wrong about that.
> 
> Ian.
>