Re: [PATCH] xen/pvhvm: If xen_platform_pci=0 is set don't blow up.

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

On Wed, Dec 04, 2013 at 11:23:40AM +0000, Ian Campbell wrote:
> On Wed, 2013-12-04 at 11:18 +0000, Stefano Stabellini wrote:
> > On Wed, 4 Dec 2013, Ian Campbell wrote:
> > > On Wed, 2013-12-04 at 11:05 +0000, Stefano Stabellini wrote:
> > > > On Wed, 4 Dec 2013, Ian Campbell wrote:
> > > > > On Wed, 2013-12-04 at 10:51 +0000, Stefano Stabellini wrote:
> > > > > > On Wed, 4 Dec 2013, Ian Campbell wrote:
> > > > > > > > +bool xen_has_pv_devices(void)
> > > > > > > > +{
> > > > > > > > +	if (!xen_domain())
> > > > > > > > +		return false;
> > > > > > > > +
> > > > > > > > +	if (xen_hvm_domain()) {
> > > > > > > > +		/* User requested no unplug, so no PV drivers. */
> > > > > > > > +		if (xen_emul_unplug & XEN_UNPLUG_NEVER)
> > > > > > > > +			return false;
> > > > > > > 
> > > > > > > I think you need
> > > > > > > 		if (xen_emul_unpug & XEN_UNPLUG_UNNECESSARY)
> > > > > > > 			return true;
> > > > > > > don't you?
> > > > > > 
> > > > > > XEN_UNPLUG_UNNECESSARY was introduced to enable the platform PCI device
> > > > > > even if it didn't respond properly to the unplug protocol.
> > > > > > The corresponding parameter is called "unnecessary" because if you pass
> > > > > > it to the kernel you mean that it is unnecessary to unplug the emulated
> > > > > > devices but you can use the pv devices anyway.
> > > > > > 
> > > > > > So no, we shouldn't check for XEN_UNPLUG_UNNECESSARY here.
> > > > > 
> > > > > Oh, we will eventually fall through to the return true, so it does
> > > > > actually work out OK.
> > > > > 
> > > > > I'd still be in favour of handling each option explicitly, for clarity.
> > > > > Which means checking for XEN_UNPLUG_UNNECESSARY.
> > > > 
> > > > I think is wrong to check for any xen_emul_unpug options in this function.
> > > > The xen_emul_unpug options should be used to set the right value of
> > > > xen_platform_pci_unplug. (See my other reply.)
> > > 
> > > Whichever one we check we should still be checking explicitly for the
> > > "unnecessary" case, for clarity if nothing else.
> > 
> > Sure, that is OK for me.
> > In that case should we check for the full list of possible options?
> 
> We probably should. That probably means an extra
> xen_has_pv_{disk,nic}_devices() which is the existing one plus the
> specific checks?

I decided to make it a bit simple and only implement the ones we
check for. Please see the patch below.

Also, I've trimmed the most of the CC list to not spam the folks --
naturally if Ian and Stefano think this is the way to go then I will
repost it.

>From bec67562eaf9f35aba233e6297c7a90cdc89d64f 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 1/2] xen/pvhvm: If xen_platform_pci=0 is set don't blow up
 (v2).

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=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.

Reported-by: Sander Eikelenboom <linux@eikelenboom.it
Reported-by: Anthony PERARD <anthony.perard@citrix.com>
Reported-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]
---
 arch/x86/xen/platform-pci-unplug.c         |   69 ++++++++++++++++++++++++++++
 drivers/block/xen-blkfront.c               |    4 +-
 drivers/char/tpm/xen-tpmfront.c            |    4 ++
 drivers/input/misc/xen-kbdfront.c          |    4 ++
 drivers/net/xen-netfront.c                 |    2 +-
 drivers/pci/xen-pcifront.c                 |    4 ++
 drivers/video/xen-fbfront.c                |    4 ++
 drivers/xen/xenbus/xenbus_probe_frontend.c |    2 +-
 include/xen/platform_pci.h                 |   23 +++++++++
 9 files changed, 112 insertions(+), 4 deletions(-)

diff --git a/arch/x86/xen/platform-pci-unplug.c b/arch/x86/xen/platform-pci-unplug.c
index 0a78524..2fb9088 100644
--- a/arch/x86/xen/platform-pci-unplug.c
+++ b/arch/x86/xen/platform-pci-unplug.c
@@ -69,6 +69,75 @@ static int check_platform_magic(void)
 	return 0;
 }
 
+bool xen_has_pv_devices()
+{
+	if (!xen_domain())
+		return false;
+
+	/* PV domains always have them. */
+	if (xen_pv_domain())
+		return true;
+
+	/* And user has xen_platform_pci=0 set in guest config as
+	 * driver did not modify the value. */
+	if (xen_platform_pci_unplug == 0)
+		return false;
+
+	if (xen_platform_pci_unplug & XEN_UNPLUG_NEVER)
+		return false;
+
+	if (xen_platform_pci_unplug & XEN_UNPLUG_ALL)
+		return true;
+
+	/* And the calleer has to follow with xen_pv_{disk,nic}_devices
+	 * to be certain which driver can load. */
+	return false;
+}
+EXPORT_SYMBOL_GPL(xen_has_pv_devices);
+
+bool __xen_has_pv_device(int state)
+{
+	/* HVM domains might or might not */
+	if (xen_hvm_domain() && (xen_platform_pci_unplug & state))
+		return true;
+
+	return xen_has_pv_devices();
+}
+
+bool xen_has_pv_nic_devices(void)
+{
+	return __xen_has_pv_device(XEN_UNPLUG_ALL_NICS | XEN_UNPLUG_ALL);
+}
+EXPORT_SYMBOL_GPL(xen_has_pv_nic_devices);
+
+bool xen_has_pv_disk_devices(void)
+{
+	return __xen_has_pv_device(XEN_UNPLUG_ALL_IDE_DISKS |
+				   XEN_UNPLUG_AUX_IDE_DISKS | XEN_UNPLUG_ALL);
+}
+EXPORT_SYMBOL_GPL(xen_has_pv_disk_devices);
+
+/*
+ * This one is odd - it determines whether you want to run PV _and_
+ * legacy (IDE) drivers together. This combination is only possible
+ * under HVM.
+ */
+bool xen_has_pv_and_legacy_disk_devices(void)
+{
+	if (!xen_domain())
+		return false;
+
+	/* N.B. This is only ever used in HVM mode */
+	if (xen_pv_domain())
+		return false;
+
+	if (xen_platform_pci_unplug & XEN_UNPLUG_UNNECESSARY)
+		return true;
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(xen_has_pv_and_legacy_disk_devices);
+
 void xen_unplug_emulated_devices(void)
 {
 	int r;
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index a4660bb..ed88b3c 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1278,7 +1278,7 @@ 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))
@@ -2022,7 +2022,7 @@ 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 94c280d..afa9362 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;
@@ -423,6 +424,9 @@ 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 e21c181..fbfdc10 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 36808bf..eea2392c 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -2106,7 +2106,7 @@ 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 f7197a7..eae7cd9 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 cd005c2..4b2d3ab 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 34b20bf..6244f9c 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;
diff --git a/include/xen/platform_pci.h b/include/xen/platform_pci.h
index 438c256..b49eeab 100644
--- a/include/xen/platform_pci.h
+++ b/include/xen/platform_pci.h
@@ -48,4 +48,27 @@ static inline int xen_must_unplug_disks(void) {
 
 extern int xen_platform_pci_unplug;
 
+#if defined(CONFIG_XEN_PVHVM)
+extern bool xen_has_pv_devices(void);
+extern bool xen_has_pv_disk_devices(void);
+extern bool xen_has_pv_nic_devices(void);
+extern bool xen_has_pv_and_legacy_disk_devices(void);
+#else
+static inline bool xen_has_pv_devices(void)
+{
+	return IS_ENABLED(CONFIG_XEN);
+}
+static inline bool xen_has_pv_disk_devices(void)
+{
+	return IS_ENABLED(CONFIG_XEN);
+}
+static inline bool xen_has_pv_nic_devices(void)
+{
+	return IS_ENABLED(CONFIG_XEN);
+}
+static inline bool xen_has_pv_and_legacy_disk_devices(void)
+{
+	return false;
+}
+#endif
 #endif /* _XEN_PLATFORM_PCI_H */
-- 
1.7.7.6