linux-toradex.git/arch/x86/xen, branch v3.12

xen: Fix possible user space selector corruption

2013-10-10T14:39:37+00:00

Due to the way kernel is initialized under Xen is possible that the
ring1 selector used by the kernel for the boot cpu end up to be copied
to userspace leading to segmentation fault in the userspace.

Xen code in the kernel initialize no-boot cpus with correct selectors (ds
and es set to __USER_DS) but the boot one keep the ring1 (passed by Xen).
On task context switch (switch_to) we assume that ds, es and cs already
point to __USER_DS and __KERNEL_CSso these selector are not changed.

If processor is an Intel that support sysenter instruction sysenter/sysexit
is used so ds and es are not restored switching back from kernel to
userspace. In the case the selectors point to a ring1 instead of __USER_DS
the userspace code will crash on first memory access attempt (to be
precise Xen on the emulated iret used to do sysexit will detect and set ds
and es to zero which lead to GPF anyway).

Now if an userspace process call kernel using sysenter and get rescheduled
(for me it happen on a specific init calling wait4) could happen that the
ring1 selector is set to ds and es.

This is quite hard to detect cause after a while these selectors are fixed
(__USER_DS seems sticky).

Bisecting the code commit 7076aada1040de4ed79a5977dbabdb5e5ea5e249 appears
to be the first one that have this issue.

Signed-off-by: Frediano Ziglio 
Signed-off-by: Stefano Stabellini 
Reviewed-by: Andrew Cooper

Merge tag 'stable/for-linus-3.12-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

2013-09-25T22:50:53+00:00

Pull Xen fixes from Konrad Rzeszutek Wilk:
 "Bug-fixes and one update to the kernel-paramters.txt documentation.

   - Fix PV spinlocks triggering jump_label code bug
   - Remove extraneous code in the tpm front driver
   - Fix ballooning out of pages when non-preemptible
   - Fix deadlock when using a 32-bit initial domain with large amount
     of memory
   - Add xen_nopvpsin parameter to the documentation"

* tag 'stable/for-linus-3.12-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/spinlock: Document the xen_nopvspin parameter.
  xen/p2m: check MFN is in range before using the m2p table
  xen/balloon: don't alloc page while non-preemptible
  xen: Do not enable spinlocks before jump_label_init() has executed
  tpm: xen-tpmfront: Remove the locality sysfs attribute
  tpm: xen-tpmfront: Fix default durations

xen/p2m: check MFN is in range before using the m2p table

2013-09-25T13:00:03+00:00

On hosts with more than 168 GB of memory, a 32-bit guest may attempt
to grant map an MFN that is error cannot lookup in its mapping of the
m2p table.  There is an m2p lookup as part of m2p_add_override() and
m2p_remove_override().  The lookup falls off the end of the mapped
portion of the m2p and (because the mapping is at the highest virtual
address) wraps around and the lookup causes a fault on what appears to
be a user space address.

do_page_fault() (thinking it's a fault to a userspace address), tries
to lock mm->mmap_sem.  If the gntdev device is used for the grant map,
m2p_add_override() is called from from gnttab_mmap() with mm->mmap_sem
already locked.  do_page_fault() then deadlocks.

The deadlock would most commonly occur when a 64-bit guest is started
and xenconsoled attempts to grant map its console ring.

Introduce mfn_to_pfn_no_overrides() which checks the MFN is within the
mapped portion of the m2p table before accessing the table and use
this in m2p_add_override(), m2p_remove_override(), and mfn_to_pfn()
(which already had the correct range check).

All faults caused by accessing the non-existant parts of the m2p are
thus within the kernel address space and exception_fixup() is called
without trying to lock mm->mmap_sem.

This means that for MFNs that are outside the mapped range of the m2p
then mfn_to_pfn() will always look in the m2p overrides.  This is
correct because it must be a foreign MFN (and the PFN in the m2p in
this case is only relevant for the other domain).

Signed-off-by: David Vrabel 
Cc: Stefano Stabellini 
Cc: Jan Beulich 
--
v3: check for auto_translated_physmap in mfn_to_pfn_no_overrides()
v2: in mfn_to_pfn() look in m2p_overrides if the MFN is out of
    range as it's probably foreign.
Signed-off-by: Konrad Rzeszutek Wilk 
Acked-by: Stefano Stabellini

xen: Do not enable spinlocks before jump_label_init() has executed

2013-09-24T20:22:26+00:00

xen_init_spinlocks() currently calls static_key_slow_inc() before
jump_label_init() is invoked. When CONFIG_JUMP_LABEL is set (which usually is
the case) the effect of this static_key_slow_inc() is deferred until after
jump_label_init(). This is different from when CONFIG_JUMP_LABEL is not set, in
which case the key is set immediately. Thus, depending on the value of config
option, we may observe different behavior.

In addition, when we come to __jump_label_transform() from jump_label_init(),
the key (paravirt_ticketlocks_enabled) is already enabled. On processors where
ideal_nop is not the same as default_nop this will cause a BUG() since it is
expected that before a key is enabled the latter is replaced by the former
during initialization.

To address this problem we need to move
static_key_slow_inc(¶virt_ticketlocks_enabled) so that it is called
after jump_label_init(). We also need to make sure that this is done before
other cpus start to boot. early_initcall appears to be  a good place to do so.
(Note that we cannot move whole xen_init_spinlocks() there since pv_lock_ops
need to be set before alternative_instructions() runs.)

Signed-off-by: Konrad Rzeszutek Wilk 
[v2: Added extra comments in the code]
Signed-off-by: Boris Ostrovsky 
Signed-off-by: Konrad Rzeszutek Wilk 
Reviewed-by: Steven Rostedt

Merge tag 'stable/for-linus-3.12-rc0-tag-two' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

2013-09-11T03:07:04+00:00

Pull Xen bug-fixes from Konrad Rzeszutek Wilk:
 "This pull I usually do after rc1 is out but because we have a nice
  amount of fixes, some bootup related fixes for ARM, and it is early in
  the cycle we figured to do it now to help with tracking of potential
  regressions.

  The simple ones are the ARM ones - one of the patches fell through the
  cracks, other fixes a bootup issue (unconditionally using Xen
  functions).  Then a fix for a regression causing preempt count being
  off (patch causing this went in v3.12).

  Lastly are the fixes to make Xen PVHVM guests use PV ticketlocks (Xen
  PV already does).

  The enablement of that was supposed to be part of the x86 spinlock
  merge in commit 816434ec4a67 ("The biggest change here are
  paravirtualized ticket spinlocks (PV spinlocks), which bring a nice
  speedup on various benchmarks...") but unfortunatly it would cause
  hang when booting Xen PVHVM guests.  Yours truly got all of the bugs
  fixed last week and they (six of them) are included in this pull.

  Bug-fixes:
   - Boot on ARM without using Xen unconditionally
   - On Xen ARM don't run cpuidle/cpufreq
   - Fix regression in balloon driver, preempt count warnings
   - Fixes to make PVHVM able to use pv ticketlock.
   - Revert Xen PVHVM disabling pv ticketlock (aka, re-enable pv ticketlocks)"

* tag 'stable/for-linus-3.12-rc0-tag-two' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/spinlock: Don't use __initdate for xen_pv_spin
  Revert "xen/spinlock: Disable IRQ spinlock (PV) allocation on PVHVM"
  xen/spinlock: Don't setup xen spinlock IPI kicker if disabled.
  xen/smp: Update pv_lock_ops functions before alternative code starts under PVHVM
  xen/spinlock: We don't need the old structure anymore
  xen/spinlock: Fix locking path engaging too soon under PVHVM.
  xen/arm: disable cpuidle and cpufreq when linux is running as dom0
  xen/p2m: Don't call get_balloon_scratch_page() twice, keep interrupts disabled for multicalls
  ARM: xen: only set pm function ptrs for Xen guests

xen/spinlock: Don't use __initdate for xen_pv_spin

2013-09-09T17:08:49+00:00

As we get compile warnings about .init.data being
used by non-init functions.

Reported-by: kbuild test robot 
Signed-off-by: Konrad Rzeszutek Wilk

Revert "xen/spinlock: Disable IRQ spinlock (PV) allocation on PVHVM"

2013-09-09T16:06:45+00:00

This reverts commit 70dd4998cb85f0ecd6ac892cc7232abefa432efb.

Now that the bugs have been resolved we can re-enable the
PV ticketlock implementation under PVHVM Xen guests.

Signed-off-by: Konrad Rzeszutek Wilk 
Reviewed-by: David Vrabel

xen/spinlock: Don't setup xen spinlock IPI kicker if disabled.

2013-09-09T16:06:38+00:00

There is no need to setup this kicker IPI if we are never going
to use the paravirtualized ticketlock mechanism.

Signed-off-by: Konrad Rzeszutek Wilk 
Reviewed-by: David Vrabel

xen/smp: Update pv_lock_ops functions before alternative code starts under PVHVM

2013-09-09T16:06:31+00:00

Before this patch we would patch all of the pv_lock_ops sites
using alternative assembler. Then later in the bootup cycle
change the unlock_kick and lock_spinning to the Xen specific -
without re patching.

That meant that for the core of the kernel we would be running
with the baremetal version of unlock_kick and lock_spinning while
for modules we would have the proper Xen specific slowpaths.

As most of the module uses some API from the core kernel that ended
up with slowpath lockers waiting forever to be kicked (b/c they
would be using the Xen specific slowpath logic). And the
kick never came b/c the unlock path that was taken was the
baremetal one.

On PV we do not have the problem as we initialise before the
alternative code kicks in.

The fix is to make the updating of the pv_lock_ops function
be done before the alternative code starts patching.

Note that this patch fixes issues discovered by commit
f10cd522c5fbfec9ae3cc01967868c9c2401ed23.
("xen: disable PV spinlocks on HVM") wherein it mentioned

PV spinlocks cannot possibly work with the current code because they are
enabled after pvops patching has already been done, and because PV
spinlocks use a different data structure than native spinlocks so we
cannot switch between them dynamically.

The first problem is solved by this patch.

The second problem has been solved by commit
816434ec4a674fcdb3c2221a6dffdc8f34020550
(Merge branch 'x86-spinlocks-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip)

P.S.
There is still the commit 70dd4998cb85f0ecd6ac892cc7232abefa432efb
(xen/spinlock: Disable IRQ spinlock (PV) allocation on PVHVM) to
revert but that can be done later after all other bugs have been
fixed.

Signed-off-by: Konrad Rzeszutek Wilk
Reviewed-by: David Vrabel

xen/spinlock: We don't need the old structure anymore

2013-09-09T16:06:24+00:00

As we are using the generic ticketlock structs and these
old structures are not needed anymore.

Signed-off-by: Konrad Rzeszutek Wilk 
Reviewed-by: David Vrabel