xen/pvhvm: If xen_platform_pci=0 is set don't blow up (v4).

The user has the option of disabling the platform driver:
00:02.0 Unassigned class [ff80]: XenSource, Inc. Xen Platform Device (rev 01)

which is used to unplug the emulated drivers (IDE, Realtek 8169, etc)
and allow the PV drivers to take over. If the user wishes
to disable that they can set:

  xen_platform_pci=0
  (in the guest config file)

or
  xen_emul_unplug=never
  (on the Linux command line)

except it does not work properly. The PV drivers still try to
load and since the Xen platform driver is not run - and it
has not initialized the grant tables, most of the PV drivers
stumble upon:

input: Xen Virtual Keyboard as /devices/virtual/input/input5
input: Xen Virtual Pointer as /devices/virtual/input/input6M
------------[ cut here ]------------
kernel BUG at /home/konrad/ssd/konrad/linux/drivers/xen/grant-table.c:1206!
invalid opcode: 0000 [#1] SMP
Modules linked in: xen_kbdfront(+) xenfs xen_privcmd
CPU: 6 PID: 1389 Comm: modprobe Not tainted 3.13.0-rc1upstream-00021-ga6c892b-dirty #1
Hardware name: Xen HVM domU, BIOS 4.4-unstable 11/26/2013
RIP: 0010:[<ffffffff813ddc40>]  [<ffffffff813ddc40>] get_free_entries+0x2e0/0x300
Call Trace:
 [<ffffffff8150d9a3>] ? evdev_connect+0x1e3/0x240
 [<ffffffff813ddd0e>] gnttab_grant_foreign_access+0x2e/0x70
 [<ffffffffa0010081>] xenkbd_connect_backend+0x41/0x290 [xen_kbdfront]
 [<ffffffffa0010a12>] xenkbd_probe+0x2f2/0x324 [xen_kbdfront]
 [<ffffffff813e5757>] xenbus_dev_probe+0x77/0x130
 [<ffffffff813e7217>] xenbus_frontend_dev_probe+0x47/0x50
 [<ffffffff8145e9a9>] driver_probe_device+0x89/0x230
 [<ffffffff8145ebeb>] __driver_attach+0x9b/0xa0
 [<ffffffff8145eb50>] ? driver_probe_device+0x230/0x230
 [<ffffffff8145eb50>] ? driver_probe_device+0x230/0x230
 [<ffffffff8145cf1c>] bus_for_each_dev+0x8c/0xb0
 [<ffffffff8145e7d9>] driver_attach+0x19/0x20
 [<ffffffff8145e260>] bus_add_driver+0x1a0/0x220
 [<ffffffff8145f1ff>] driver_register+0x5f/0xf0
 [<ffffffff813e55c5>] xenbus_register_driver_common+0x15/0x20
 [<ffffffff813e76b3>] xenbus_register_frontend+0x23/0x40
 [<ffffffffa0015000>] ? 0xffffffffa0014fff
 [<ffffffffa001502b>] xenkbd_init+0x2b/0x1000 [xen_kbdfront]
 [<ffffffff81002049>] do_one_initcall+0x49/0x170

.. snip..

which is hardly nice. This patch fixes this by having each
PV driver check for:
 - if running in PV, then it is fine to execute (as that is their
   native environment).
 - if running in HVM, check if user wanted 'xen_emul_unplug=never',
   in which case bail out and don't load any PV drivers.
 - if running in HVM, and if PCI device 5853:0001 (xen_platform_pci)
   does not exist, then bail out and not load PV drivers.
 - (v2) if running in HVM, and if the user wanted 'xen_emul_unplug=ide-disks',
   then bail out for all PV devices _except_ the block one.
   Ditto for the network one ('nics').
 - (v2) if running in HVM, and if the user wanted 'xen_emul_unplug=unnecessary'
   then load block PV driver, and also setup the legacy IDE paths.
   In (v3) make it actually load PV drivers.

Reported-by: Sander Eikelenboom <linux@eikelenboom.it
Reported-by: Anthony PERARD <anthony.perard@citrix.com>
Reported-and-Tested-by: Fabio Fantoni <fabio.fantoni@m2r.biz>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[v2: Add extra logic to handle the myrid ways 'xen_emul_unplug'
can be used per Ian and Stefano suggestion]
[v3: Make the unnecessary case work properly]
[v4: s/disks/ide-disks/ spotted by Fabio]
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> [for PCI parts]
CC: stable@vger.kernel.org

7 files changed, 20 insertions, 4 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index c4a4c9006288..f9c43f91f03e 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1356,7 +1356,7 @@ static int blkfront_probe(struct xenbus_device *dev,
 		char *type;
 		int len;
 		/* no unplug has been done: do not hook devices != xen vbds */
-		if (xen_platform_pci_unplug & XEN_UNPLUG_UNNECESSARY) {
+		if (xen_has_pv_and_legacy_disk_devices()) {
 			int major;
 
 			if (!VDEV_IS_EXTENDED(vdevice))
@@ -2079,7 +2079,7 @@ static int __init xlblk_init(void)
 	if (!xen_domain())
 		return -ENODEV;
 
-	if (xen_hvm_domain() && !xen_platform_pci_unplug)
+	if (!xen_has_pv_disk_devices())
 		return -ENODEV;
 
 	if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
index c8ff4df81779..62e7d383fa64 100644
--- a/drivers/char/tpm/xen-tpmfront.c
+++ b/drivers/char/tpm/xen-tpmfront.c
@@ -17,6 +17,7 @@
 #include <xen/xenbus.h>
 #include <xen/page.h>
 #include "tpm.h"
+#include <xen/platform_pci.h>
 
 struct tpm_private {
 	struct tpm_chip *chip;
@@ -421,6 +422,9 @@ static int __init xen_tpmfront_init(void)
 	if (!xen_domain())
 		return -ENODEV;
 
+	if (!xen_has_pv_devices())
+		return -ENODEV;
+
 	return xenbus_register_frontend(&tpmfront_driver);
 }
 module_init(xen_tpmfront_init);
diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
index e21c1816a8f9..fbfdc10573be 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_has_pv_devices())
+		return -ENODEV;
+
 	return xenbus_register_frontend(&xenkbd_driver);
 }
 
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index e59acb1daa23..2ab82fe75ede 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_has_pv_nic_devices())
 		return -ENODEV;
 
 	pr_info("Initialising Xen virtual ethernet driver\n");
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index f7197a790341..eae7cd9fde7b 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -20,6 +20,7 @@
 #include <linux/workqueue.h>
 #include <linux/bitops.h>
 #include <linux/time.h>
+#include <xen/platform_pci.h>
 
 #include <asm/xen/swiotlb-xen.h>
 #define INVALID_GRANT_REF (0)
@@ -1138,6 +1139,9 @@ static int __init pcifront_init(void)
 	if (!xen_pv_domain() || xen_initial_domain())
 		return -ENODEV;
 
+	if (!xen_has_pv_devices())
+		return -ENODEV;
+
 	pci_frontend_registrar(1 /* enable */);
 
 	return xenbus_register_frontend(&xenpci_driver);
diff --git a/drivers/video/xen-fbfront.c b/drivers/video/xen-fbfront.c
index cd005c227a23..4b2d3ab870f3 100644
--- a/drivers/video/xen-fbfront.c
+++ b/drivers/video/xen-fbfront.c
@@ -35,6 +35,7 @@
 #include <xen/interface/io/fbif.h>
 #include <xen/interface/io/protocols.h>
 #include <xen/xenbus.h>
+#include <xen/platform_pci.h>
 
 struct xenfb_info {
 	unsigned char		*fb;
@@ -699,6 +700,9 @@ static int __init xenfb_init(void)
 	if (xen_initial_domain())
 		return -ENODEV;
 
+	if (!xen_has_pv_devices())
+		return -ENODEV;
+
 	return xenbus_register_frontend(&xenfb_driver);
 }
 
diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
index 129bf84c19ec..cb385c10d2b1 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_has_pv_devices())
 		return -ENODEV;
 
 	ready_to_wait_for_devices = 1;