Re: [Xen-devel] [PATCH v3 1/2] xen/pvhvm: If xen_platform_pci=0 is set don't blow up (v3).

[Fabio Fantoni <fabio.fantoni@m2r.biz>]

Il 16/12/2013 16:04, Konrad Rzeszutek Wilk ha scritto:
> 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.
>     In (v3) make it actually load PV drivers.
>
> 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]
> [v3: Make the unnecessary case work properly]
> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

I tested this patch with all possible cases that I know, no crash or 
calltrace found.

I don't understand the utility of 'xen_emul_unplug=unnecessary' but 
probably it is working correctly, it shows both pv and not pv for blocks 
and nics.

About 'xen_emul_unplug=disks' and 'xen_emul_unplug=nics' probably there 
is something wrong.
With 'xen_emul_unplug=nics' it shows pv nic (this should be correct) and 
about disks it shows the same disk twice, as pv and not pv (xvda and 
sda) with different device number.
With 'xen_emul_unplug=disks' it shows pv block (this should be correct) 
and it seems to show the pv nic too (this should be wrong).

Thanks for any reply.

> ---
>   arch/x86/xen/platform-pci-unplug.c         | 74 ++++++++++++++++++++++++++++++
>   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, 117 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/xen/platform-pci-unplug.c b/arch/x86/xen/platform-pci-unplug.c
> index 0a78524..ab84ac1 100644
> --- a/arch/x86/xen/platform-pci-unplug.c
> +++ b/arch/x86/xen/platform-pci-unplug.c
> @@ -69,6 +69,80 @@ 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;
> +
> +	/* This is an odd one - we are going to run legacy
> +	 * and PV drivers at the same time. */
> +	if (xen_platform_pci_unplug & XEN_UNPLUG_UNNECESSARY)
> +		return true;
> +
> +	/* And the caller 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);
> +
> +static 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 06189e5..9c2cbd1 100644
> --- a/drivers/char/tpm/xen-tpmfront.c
> +++ b/drivers/char/tpm/xen-tpmfront.c
> @@ -16,6 +16,7 @@
>   #include <xen/xenbus.h>
>   #include <xen/page.h>
>   #include "tpm.h"
> +#include <xen/platform_pci.h>
>   
>   struct tpm_private {
>   	struct tpm_chip *chip;
> @@ -422,6 +423,9 @@ 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..eea2392 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 */