linux-stable.git/arch/powerpc/kernel, branch v3.12

powerpc/irq: Don't switch to irq stack from softirq stack

2013-10-07T21:19:39+00:00

irq_exit() is now called on the irq stack, which can trigger a switch to
the softirq stack from the irq stack.  If an interrupt happens at that
point, we will not properly detect the re-entrancy and clobber the
original return context on the irq stack.

This fixes it.  The side effect is to prevent all nesting from softirq
stack to irq stack even in the "safe" case but it's simpler that way and
matches what x86_64 does.

Reported-by: Cédric Le Goater 
Tested-by: Cédric Le Goater 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Linus Torvalds

powerpc/tm: Switch out userspace PPR and DSCR sooner

2013-10-03T07:25:51+00:00

When we do a treclaim or trecheckpoint we end up running with userspace
PPR and DSCR values.  Currently we don't do anything special to avoid
running with user values which could cause a severe performance
degradation.

This patch moves the PPR and DSCR save and restore around treclaim and
trecheckpoint so that we run with user values for a much shorter period.
More care is taken with the PPR as it's impact is greater than the DSCR.

This is similar to user exceptions, where we run HTM_MEDIUM early to
ensure that we don't run with a userspace PPR values in the kernel.

Signed-off-by: Michael Neuling 
Cc:  # 3.9+
Signed-off-by: Benjamin Herrenschmidt

powerpc/tm: Turn interrupts hard off in tm_reclaim()

2013-10-03T07:25:44+00:00

We can't take IRQs in tm_reclaim as we might have a bogus r13 and r1.

This turns IRQs hard off in this function.

Signed-off-by: Michael Neuling 
Cc:  # 3.9+
Signed-off-by: Benjamin Herrenschmidt

powerpc/vio: Fix modalias_show return values

2013-10-03T07:25:16+00:00

modalias_show() should return an empty string on error, not -ENODEV.

This causes the following false and annoying error:

> find /sys/devices -name modalias -print0 | xargs -0 cat >/dev/null
cat: /sys/devices/vio/4000/modalias: No such device
cat: /sys/devices/vio/4001/modalias: No such device
cat: /sys/devices/vio/4002/modalias: No such device
cat: /sys/devices/vio/4004/modalias: No such device
cat: /sys/devices/vio/modalias: No such device

Signed-off-by: Prarit Bhargava 
Signed-off-by: Benjamin Herrenschmidt 
CC:

powerpc/iommu: Use GFP_KERNEL instead of GFP_ATOMIC in iommu_init_table()

2013-10-03T07:24:44+00:00

Under heavy (DLPAR?) stress, we tripped this panic() in
arch/powerpc/kernel/iommu.c::iommu_init_table():

	page = alloc_pages_node(nid, GFP_ATOMIC, get_order(sz));
	if (!page)
		panic("iommu_init_table: Can't allocate %ld bytes\n", sz);

Before the panic() we got a page allocation failure for an order-2
allocation. There appears to be memory free, but perhaps not in the
ATOMIC context. I looked through all the call-sites of
iommu_init_table() and didn't see any obvious reason to need an ATOMIC
allocation. Most call-sites in fact have an explicit GFP_KERNEL
allocation shortly before the call to iommu_init_table(), indicating we
are not in an atomic context. There is some indirection for some paths,
but I didn't see any locks indicating that GFP_KERNEL is inappropriate.

With this change under the same conditions, we have not been able to
reproduce the panic.

Signed-off-by: Nishanth Aravamudan 
Signed-off-by: Benjamin Herrenschmidt 
CC:

powerpc/sysfs: Disable writing to PURR in guest mode

2013-10-03T07:22:53+00:00

arch/powerpc/kernel/sysfs.c exports PURR with write permission.
This may be valid for kernel in phyp mode. But writing to
the file in guest mode causes crash due to a priviledge violation

Signed-off-by: Madhavan Srinivasan 
Signed-off-by: Benjamin Herrenschmidt 
CC:

powerpc/pseries: Do not start secondaries in Open Firmware

2013-09-25T04:19:00+00:00

Starting secondary CPUs early on from Open Firmware and placing them
in a holding spin loop slows down the boot process significantly under
some hypervisors such as KVM.

This is also unnecessary when RTAS supports querying the CPU state

So let's not do it.

Signed-off-by: Benjamin Herrenschmidt

powerpc: Remove ksp_limit on ppc64

2013-09-25T04:15:51+00:00

We've been keeping that field in thread_struct for a while, it contains
the "limit" of the current stack pointer and is meant to be used for
detecting stack overflows.

It has a few problems however:

 - First, it was never actually *used* on 64-bit. Set and updated but
not actually exploited

 - When switching stack to/from irq and softirq stacks, it's update
is racy unless we hard disable interrupts, which is costly. This
is fine on 32-bit as we don't soft-disable there but not on 64-bit.

Thus rather than fixing 2 in order to implement 1 in some hypothetical
future, let's remove the code completely from 64-bit. In order to avoid
a clutter of ifdef's, we remove the updates from C code completely
during interrupt stack switching, and instead maintain it from the
asm helper that is used to do the stack switching in the first place.

Signed-off-by: Benjamin Herrenschmidt

powerpc/irq: Run softirqs off the top of the irq stack

2013-09-25T04:15:36+00:00

Nowadays, irq_exit() calls __do_softirq() pretty much directly
instead of calling do_softirq() which switches to the decicated
softirq stack.

This has lead to observed stack overflows on powerpc since we call
irq_enter() and irq_exit() outside of the scope that switches to
the irq stack.

This fixes it by moving the stack switching up a level, making
irq_enter() and irq_exit() run off the irq stack.

Signed-off-by: Benjamin Herrenschmidt

powerpc: Fix section mismatch warning for prom_rtas_call

2013-09-11T01:39:38+00:00

While cross-building for PPC64 I've got

WARNING: vmlinux.o(.text.unlikely+0x1ba): Section mismatch in
reference from the function .prom_rtas_call() to the variable
.init.data:dt_string_start The function .prom_rtas_call() references
the variable __initdata dt_string_start.  This is often because
.prom_rtas_call lacks a __initdata annotation or the annotation of
dt_string_start is wrong.

WARNING: vmlinux.o(.meminit.text+0xeb0): Section mismatch in reference
from the function .free_area_init_core.isra.47() to the function
.init.text:.set_pageblock_order() The function __meminit
.free_area_init_core.isra.47() references a function __init
.set_pageblock_order().  If .set_pageblock_order is only used by
.free_area_init_core.isra.47 then annotate .set_pageblock_order with a
matching annotation.

Fix it by proper annotation of prom_rtas_call.

Signed-off-by: Vladimir Murzin 
Signed-off-by: Benjamin Herrenschmidt