On Tue, 2013-12-03 at 16:14 -0500, Konrad Rzeszutek Wilk wrote:
> 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 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.
>
> P.S.
> Ian Campbell suggested getting rid of 'xen_platform_pci_unplug'
> but unfortunatly the xen-blkfront driver is using it, so we
> cannot do it.
It might still be nice to expose a suitable semantic interface (i.e.
some relevant predicate) rather than the raw value for blkfront to use.
But that can be a future thing I think.
> Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx
> Reported-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> Reported-by: Fabio Fantoni <fabio.fantoni@xxxxxxx>
> ---
> arch/x86/xen/platform-pci-unplug.c | 18 ++++++++++++++++++
> drivers/block/xen-blkfront.c | 2 +-
> 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 | 13 ++++++++++++-
> 9 files changed, 49 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/xen/platform-pci-unplug.c b/arch/x86/xen/platform-pci-unplug.c
> index 0a78524..087dfeb 100644
> --- a/arch/x86/xen/platform-pci-unplug.c
> +++ b/arch/x86/xen/platform-pci-unplug.c
> @@ -69,6 +69,24 @@ static int check_platform_magic(void)
> return 0;
> }
>
> +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?
> + /* And user has xen_platform_pci=0 set in guest config as
> + * driver did not modify the value. */
> + if (!xen_platform_pci_unplug)
> + return false;
> + }
> + return true;
> +}
> +EXPORT_SYMBOL_GPL(xen_has_pv_devices);
> +
> void xen_unplug_emulated_devices(void)
> {
> int r;
--
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