linux-toradex.git/arch, branch v2.6.32.50 Linux kernel for Apalis and Colibri modules oprofile, x86: Fix crash when unloading module (nmi timer mode) 2011-12-09T17:21:50+00:00 Robert Richter robert.richter@amd.com 2011-10-10T14:21:10+00:00 b669d5d9173f5f8d0e84744bc03e19d7f94f36ed commit 97f7f8189fe54e3cfe324ef9ad35064f3d2d3bff upstream. If oprofile uses the nmi timer interrupt there is a crash while unloading the module. The bug can be triggered with oprofile build as module and kernel parameter nolapic set. This patch fixes this. oprofile: using NMI timer interrupt. BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 IP: [<ffffffff8123c226>] unregister_syscore_ops+0x41/0x58 PGD 42dbca067 PUD 41da6a067 PMD 0 Oops: 0002 [#1] PREEMPT SMP CPU 5 Modules linked in: oprofile(-) [last unloaded: oprofile] Pid: 2518, comm: modprobe Not tainted 3.1.0-rc7-00019-gb2fb49d #19 Advanced Micro Device Anaheim/Anaheim RIP: 0010:[<ffffffff8123c226>] [<ffffffff8123c226>] unregister_syscore_ops+0x41/0x58 RSP: 0018:ffff88041ef71e98 EFLAGS: 00010296 RAX: 0000000000000000 RBX: ffffffffa0017100 RCX: dead000000200200 RDX: 0000000000000000 RSI: dead000000100100 RDI: ffffffff8178c620 RBP: ffff88041ef71ea8 R08: 0000000000000001 R09: 0000000000000082 R10: 0000000000000000 R11: ffff88041ef71de8 R12: 0000000000000080 R13: fffffffffffffff5 R14: 0000000000000001 R15: 0000000000610210 FS: 00007fc902f20700(0000) GS:ffff88042fd40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 0000000000000008 CR3: 000000041cdb6000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process modprobe (pid: 2518, threadinfo ffff88041ef70000, task ffff88041d348040) Stack: ffff88041ef71eb8 ffffffffa0017790 ffff88041ef71eb8 ffffffffa0013532 ffff88041ef71ec8 ffffffffa00132d6 ffff88041ef71ed8 ffffffffa00159b2 ffff88041ef71f78 ffffffff81073115 656c69666f72706f 0000000000610200 Call Trace: [<ffffffffa0013532>] op_nmi_exit+0x15/0x17 [oprofile] [<ffffffffa00132d6>] oprofile_arch_exit+0xe/0x10 [oprofile] [<ffffffffa00159b2>] oprofile_exit+0x1e/0x20 [oprofile] [<ffffffff81073115>] sys_delete_module+0x1c3/0x22f [<ffffffff811bf09e>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff8148070b>] system_call_fastpath+0x16/0x1b Code: 20 c6 78 81 e8 c5 cc 23 00 48 8b 13 48 8b 43 08 48 be 00 01 10 00 00 00 ad de 48 b9 00 02 20 00 00 00 ad de 48 c7 c7 20 c6 78 81 89 42 08 48 89 10 48 89 33 48 89 4b 08 e8 a6 c0 23 00 5a 5b RIP [<ffffffff8123c226>] unregister_syscore_ops+0x41/0x58 RSP <ffff88041ef71e98> CR2: 0000000000000008 ---[ end trace 43a541a52956b7b0 ]--- Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit 97f7f8189fe54e3cfe324ef9ad35064f3d2d3bff upstream.

If oprofile uses the nmi timer interrupt there is a crash while
unloading the module. The bug can be triggered with oprofile build as
module and kernel parameter nolapic set. This patch fixes this.

oprofile: using NMI timer interrupt.
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: [<ffffffff8123c226>] unregister_syscore_ops+0x41/0x58
PGD 42dbca067 PUD 41da6a067 PMD 0
Oops: 0002 [#1] PREEMPT SMP
CPU 5
Modules linked in: oprofile(-) [last unloaded: oprofile]

Pid: 2518, comm: modprobe Not tainted 3.1.0-rc7-00019-gb2fb49d #19 Advanced Micro Device Anaheim/Anaheim
RIP: 0010:[<ffffffff8123c226>]  [<ffffffff8123c226>] unregister_syscore_ops+0x41/0x58
RSP: 0018:ffff88041ef71e98  EFLAGS: 00010296
RAX: 0000000000000000 RBX: ffffffffa0017100 RCX: dead000000200200
RDX: 0000000000000000 RSI: dead000000100100 RDI: ffffffff8178c620
RBP: ffff88041ef71ea8 R08: 0000000000000001 R09: 0000000000000082
R10: 0000000000000000 R11: ffff88041ef71de8 R12: 0000000000000080
R13: fffffffffffffff5 R14: 0000000000000001 R15: 0000000000610210
FS:  00007fc902f20700(0000) GS:ffff88042fd40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000008 CR3: 000000041cdb6000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process modprobe (pid: 2518, threadinfo ffff88041ef70000, task ffff88041d348040)
Stack:
 ffff88041ef71eb8 ffffffffa0017790 ffff88041ef71eb8 ffffffffa0013532
 ffff88041ef71ec8 ffffffffa00132d6 ffff88041ef71ed8 ffffffffa00159b2
 ffff88041ef71f78 ffffffff81073115 656c69666f72706f 0000000000610200
Call Trace:
 [<ffffffffa0013532>] op_nmi_exit+0x15/0x17 [oprofile]
 [<ffffffffa00132d6>] oprofile_arch_exit+0xe/0x10 [oprofile]
 [<ffffffffa00159b2>] oprofile_exit+0x1e/0x20 [oprofile]
 [<ffffffff81073115>] sys_delete_module+0x1c3/0x22f
 [<ffffffff811bf09e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
 [<ffffffff8148070b>] system_call_fastpath+0x16/0x1b
Code: 20 c6 78 81 e8 c5 cc 23 00 48 8b 13 48 8b 43 08 48 be 00 01 10 00 00 00 ad de 48 b9 00 02 20 00 00 00 ad de 48 c7 c7 20 c6 78 81
 89 42 08 48 89 10 48 89 33 48 89 4b 08 e8 a6 c0 23 00 5a 5b
RIP  [<ffffffff8123c226>] unregister_syscore_ops+0x41/0x58
 RSP <ffff88041ef71e98>
CR2: 0000000000000008
---[ end trace 43a541a52956b7b0 ]---

Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
x86/mpparse: Account for bus types other than ISA and PCI 2011-12-09T17:21:49+00:00 Bjorn Helgaas bhelgaas@google.com 2011-09-25T21:29:00+00:00 98e64d37b7cf1b2ce17ac7fd65da16fb708ff738 commit 9e6866686bdf2dcf3aeb0838076237ede532dcc8 upstream. In commit f8924e770e04 ("x86: unify mp_bus_info"), the 32-bit and 64-bit versions of MP_bus_info were rearranged to match each other better. Unfortunately it introduced a regression: prior to that change we used to always set the mp_bus_not_pci bit, then clear it if we found a PCI bus. After it, we set mp_bus_not_pci for ISA buses, clear it for PCI buses, and leave it alone otherwise. In the cases of ISA and PCI, there's not much difference. But ISA is not the only non-PCI bus, so it's better to always set mp_bus_not_pci and clear it only for PCI. Without this change, Dan's Dell PowerEdge 4200 panics on boot with a log indicating interrupt routing trouble unless the "noapic" option is supplied. With this change, the machine boots reliably without "noapic". Fixes http://bugs.debian.org/586494 Reported-bisected-and-tested-by: Dan McGrath <troubledaemon@gmail.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Cc: Dan McGrath <troubledaemon@gmail.com> Cc: Alexey Starikovskiy <aystarik@gmail.com> [jrnieder@gmail.com: clarified commit message] Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Link: http://lkml.kernel.org/r/20111122215000.GA9151@elie.hsd1.il.comcast.net Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit 9e6866686bdf2dcf3aeb0838076237ede532dcc8 upstream.

In commit f8924e770e04 ("x86: unify mp_bus_info"), the 32-bit
and 64-bit versions of MP_bus_info were rearranged to match each
other better.  Unfortunately it introduced a regression: prior
to that change we used to always set the mp_bus_not_pci bit,
then clear it if we found a PCI bus.  After it, we set
mp_bus_not_pci for ISA buses, clear it for PCI buses, and leave
it alone otherwise.

In the cases of ISA and PCI, there's not much difference.  But
ISA is not the only non-PCI bus, so it's better to always set
mp_bus_not_pci and clear it only for PCI.

Without this change, Dan's Dell PowerEdge 4200 panics on boot
with a log indicating interrupt routing trouble unless the
"noapic" option is supplied.  With this change, the machine
boots reliably without "noapic".

Fixes http://bugs.debian.org/586494

Reported-bisected-and-tested-by: Dan McGrath <troubledaemon@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Dan McGrath <troubledaemon@gmail.com>
Cc: Alexey Starikovskiy <aystarik@gmail.com>
[jrnieder@gmail.com: clarified commit message]
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Link: http://lkml.kernel.org/r/20111122215000.GA9151@elie.hsd1.il.comcast.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
sched, x86: Avoid unnecessary overflow in sched_clock 2011-12-09T17:21:48+00:00 Salman Qazi sqazi@google.com 2011-11-15T22:12:06+00:00 e52d3fb7c83d6cb569f343a3db9b45decc801f59 commit 4cecf6d401a01d054afc1e5f605bcbfe553cb9b9 upstream. (Added the missing signed-off-by line) In hundreds of days, the __cycles_2_ns calculation in sched_clock has an overflow. cyc * per_cpu(cyc2ns, cpu) exceeds 64 bits, causing the final value to become zero. We can solve this without losing any precision. We can decompose TSC into quotient and remainder of division by the scale factor, and then use this to convert TSC into nanoseconds. Signed-off-by: Salman Qazi <sqazi@google.com> Acked-by: John Stultz <johnstul@us.ibm.com> Reviewed-by: Paul Turner <pjt@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20111115221121.7262.88871.stgit@dungbeetle.mtv.corp.google.com Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit 4cecf6d401a01d054afc1e5f605bcbfe553cb9b9 upstream.

(Added the missing signed-off-by line)

In hundreds of days, the __cycles_2_ns calculation in sched_clock
has an overflow.  cyc * per_cpu(cyc2ns, cpu) exceeds 64 bits, causing
the final value to become zero.  We can solve this without losing
any precision.

We can decompose TSC into quotient and remainder of division by the
scale factor, and then use this to convert TSC into nanoseconds.

Signed-off-by: Salman Qazi <sqazi@google.com>
Acked-by: John Stultz <johnstul@us.ibm.com>
Reviewed-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111115221121.7262.88871.stgit@dungbeetle.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
ARM: 7161/1: errata: no automatic store buffer drain 2011-12-09T17:21:36+00:00 Will Deacon will.deacon@arm.com 2011-11-14T16:24:58+00:00 b94342e75946ed88a3048602390633b9f047d5f2 commit 11ed0ba1754841316d4095478944300acf19acc3 upstream. This patch implements a workaround for PL310 erratum 769419. On revisions of the PL310 prior to r3p2, the Store Buffer does not automatically drain. This can cause normal, non-cacheable writes to be retained when the memory system is idle, leading to suboptimal I/O performance for drivers using coherent DMA. This patch adds an optional wmb() call to the cpu_idle loop. On systems with an outer cache, this causes an explicit flush of the store buffer. Acked-by: Catalin Marinas <catalin.marinas@arm.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit 11ed0ba1754841316d4095478944300acf19acc3 upstream.

This patch implements a workaround for PL310 erratum 769419. On
revisions of the PL310 prior to r3p2, the Store Buffer does not
automatically drain. This can cause normal, non-cacheable writes to be
retained when the memory system is idle, leading to suboptimal I/O
performance for drivers using coherent DMA.

This patch adds an optional wmb() call to the cpu_idle loop. On systems
with an outer cache, this causes an explicit flush of the store buffer.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
tty: icount changeover for other main devices 2011-11-26T17:10:38+00:00 Alan Cox alan@linux.intel.com 2011-11-13T15:25:20+00:00 9345f184dad224ff5ed726a7b67ca999384de262 commit 0587102cf9f427c185bfdeb2cef41e13ee0264b1 upstream Again basically cut and paste Convert the main driver set to use the hooks for GICOUNT Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> 
commit 0587102cf9f427c185bfdeb2cef41e13ee0264b1 upstream

Again basically cut and paste

Convert the main driver set to use the hooks for GICOUNT

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Revert "powerpc/mpic: Fix problem that affinity is not updated" 2011-11-09T00:02:23+00:00 Greg Kroah-Hartman gregkh@suse.de 2011-11-08T23:44:02+00:00 331dd2ccbb70bd7193be65bfa036b3658ccf0405 This reverts commit 1badd98ea79b7b20fb4ddfea110d1bb99c33a55f. It breaks the build on powerpc systems: arch/powerpc/sysdev/mpic.c: In function 'irq_choose_cpu': arch/powerpc/sysdev/mpic.c:574: error: passing argument 1 of '__cpus_equal' from incompatible pointer type Reported-by: Jiri Slaby <jslaby@suse.cz> Cc: Jiajun Wu <b06378@freescale.com> Cc: Li Yang <leoli@freescale.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
This reverts commit 1badd98ea79b7b20fb4ddfea110d1bb99c33a55f.

It breaks the build on powerpc systems:

arch/powerpc/sysdev/mpic.c: In function 'irq_choose_cpu':
arch/powerpc/sysdev/mpic.c:574: error: passing argument 1 of '__cpus_equal' from incompatible pointer type

Reported-by: Jiri Slaby <jslaby@suse.cz>
Cc: Jiajun Wu <b06378@freescale.com>
Cc: Li Yang <leoli@freescale.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Revert "MIPS: MTX-1: Make au1000_eth probe all PHY 2011-11-07T20:32:44+00:00 Florian Fainelli florian@openwrt.org 2011-10-17T17:43:06+00:00 0804bd48bb9787acf5ae7d2f155fdea11d198018 Commit ec3eb823 was not applicable in 2.6.32 and introduces a build breakage. Revert that commit since it is irrelevant for this kernel version. Acked-by: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Florian Fainelli <florian@openwrt.org> 
Commit ec3eb823 was not applicable in 2.6.32 and introduces a build breakage.
Revert that commit since it is irrelevant for this kernel version.

Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
KVM: x86: Reset tsc_timestamp on TSC writes 2011-11-07T20:32:42+00:00 Philipp Hahn hahn@univention.de 2011-09-12T15:52:51+00:00 f8723d9144b7bc47a8ab994bad990508c1ab848c There is no upstream commit ID for this patch since it is not a straight backport from upstream. It is a fix only relevant to 2.6.32.y. Since 1d5f066e0b63271b67eac6d3752f8aa96adcbddb from 2.6.37 was back-ported to 2.6.32.40 as ad2088cabe0fd7f633f38ba106025d33ed9a2105, the following patch is needed to add the needed reset logic to 2.6.32 as well. Bug #23257: Reset tsc_timestamp on TSC writes vcpu->last_guest_tsc is updated in vcpu_enter_guest() and kvm_arch_vcpu_put() by getting the last value of the TSC from the guest. On reset, the SeaBIOS resets the TSC to 0, which triggers a bug on the next call to kvm_write_guest_time(): Since vcpu->hw_clock.tsc_timestamp still contains the old value before the reset, "max_kernel_ns = vcpu->last_guest_tsc - vcpu->hw_clock.tsc_timestamp" gets negative. Since the variable is u64, it gets translated to a large positive value. [9333.197080] vcpu->last_guest_tsc =209_328_760_015 ← vcpu->hv_clock.tsc_timestamp=209_328_708_109 vcpu->last_kernel_ns =9_333_179_830_643 kernel_ns =9_333_197_073_429 max_kernel_ns =9_333_179_847_943 ← [9336.910995] vcpu->last_guest_tsc =9_438_510_584 ← vcpu->hv_clock.tsc_timestamp=211_080_593_143 vcpu->last_kernel_ns =9_333_763_732_907 kernel_ns =9_336_910_990_771 max_kernel_ns =6_148_296_831_006_663_830 ← For completeness, here are the values for my 3 GHz CPU: vcpu->hv_clock.tsc_shift =-1 vcpu->hv_clock.tsc_to_system_mul =2_863_019_502 This makes the guest kernel crawl very slowly when clocksource=kvmclock is used: sleeps take way longer than expected and don't match wall clock any more. The times printed with printk() don't match real time and the reboot often stalls for long times. In linux-git this isn't a problem, since on every MSR_IA32_TSC write vcpu->arch.hv_clock.tsc_timestamp is reset to 0, which disables above logic. The code there is only in arch/x86/kvm/x86.c, since much of the kvm-clock related code has been refactured for 2.6.37: 99e3e30a arch/x86/kvm/x86.c (Zachary Amsden 2010-08-19 22:07:17 -1000 1084) vcpu->arch.hv_clock.tsc_timestamp = 0; Signed-off-by: Philipp Hahn <hahn@univention.de> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
There is no upstream commit ID for this patch since it is not a straight
backport from upstream. It is a fix only relevant to 2.6.32.y.

Since 1d5f066e0b63271b67eac6d3752f8aa96adcbddb from 2.6.37 was
back-ported to 2.6.32.40 as ad2088cabe0fd7f633f38ba106025d33ed9a2105,
the following patch is needed to add the needed reset logic to 2.6.32 as
well.


Bug #23257: Reset tsc_timestamp on TSC writes

vcpu->last_guest_tsc is updated in vcpu_enter_guest() and kvm_arch_vcpu_put()
by getting the last value of the TSC from the guest.
On reset, the SeaBIOS resets the TSC to 0, which triggers a bug on the next
call to kvm_write_guest_time(): Since vcpu->hw_clock.tsc_timestamp still
contains the old value before the reset, "max_kernel_ns = vcpu->last_guest_tsc
- vcpu->hw_clock.tsc_timestamp" gets negative. Since the variable is u64, it
 gets translated to a large positive value.

[9333.197080]
vcpu->last_guest_tsc        =209_328_760_015           ←
vcpu->hv_clock.tsc_timestamp=209_328_708_109
vcpu->last_kernel_ns        =9_333_179_830_643
kernel_ns                   =9_333_197_073_429
max_kernel_ns               =9_333_179_847_943         ←

[9336.910995]
vcpu->last_guest_tsc        =9_438_510_584             ←
vcpu->hv_clock.tsc_timestamp=211_080_593_143
vcpu->last_kernel_ns        =9_333_763_732_907
kernel_ns                   =9_336_910_990_771
max_kernel_ns               =6_148_296_831_006_663_830 ←

For completeness, here are the values for my 3 GHz CPU:
vcpu->hv_clock.tsc_shift         =-1
vcpu->hv_clock.tsc_to_system_mul =2_863_019_502

This makes the guest kernel crawl very slowly when clocksource=kvmclock is
used: sleeps take way longer than expected and don't match wall clock any more.
The times printed with printk() don't match real time and the reboot often
stalls for long times.

In linux-git this isn't a problem, since on every MSR_IA32_TSC write
vcpu->arch.hv_clock.tsc_timestamp is reset to 0, which disables above logic.
The code there is only in arch/x86/kvm/x86.c, since much of the kvm-clock
related code has been refactured for 2.6.37:
	99e3e30a arch/x86/kvm/x86.c 
        (Zachary Amsden            2010-08-19 22:07:17 -1000 1084)
        vcpu->arch.hv_clock.tsc_timestamp = 0;                                                      

Signed-off-by: Philipp Hahn <hahn@univention.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
xen/timer: Missing IRQF_NO_SUSPEND in timer code broke suspend. 2011-11-07T20:32:42+00:00 Ian Campbell Ian.Campbell@citrix.com 2011-02-08T14:03:31+00:00 e4ce2d7e6b2f75d5a8a82b326d153b6fe9d3ac06 commit f611f2da99420abc973c32cdbddbf5c365d0a20c upstream. The patches missed an indirect use of IRQF_NO_SUSPEND pulled in via IRQF_TIMER. The following patch fixes the issue. With this fixlet PV guest migration works just fine. I also booted the entire series as a dom0 kernel and it appeared fine. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit f611f2da99420abc973c32cdbddbf5c365d0a20c upstream.

The patches missed an indirect use of IRQF_NO_SUSPEND pulled in via
IRQF_TIMER. The following patch fixes the issue.

With this fixlet PV guest migration works just fine. I also booted the
entire series as a dom0 kernel and it appeared fine.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
um: fix ubd cow size 2011-11-07T20:32:38+00:00 Richard Weinberger richard@nod.at 2011-11-02T12:17:27+00:00 610fba92198e257bb039e49c391bb73cd0c1b2b1 commit 8535639810e578960233ad39def3ac2157b0c3ec upstream. ubd_file_size() cannot use ubd_dev->cow.file because at this time ubd_dev->cow.file is not initialized. Therefore, ubd_file_size() will always report a wrong disk size when COW files are used. Reading from /dev/ubd* would crash the kernel. We have to read the correct disk size from the COW file's backing file. Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit 8535639810e578960233ad39def3ac2157b0c3ec upstream.

ubd_file_size() cannot use ubd_dev->cow.file because at this time
ubd_dev->cow.file is not initialized.
Therefore, ubd_file_size() will always report a wrong disk size when
COW files are used.
Reading from /dev/ubd* would crash the kernel.

We have to read the correct disk size from the COW file's backing
file.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>